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Agronomical, physiological and fruit quality responses of two Italian long-storage tomato landraces under rain-fed and full irrigation conditions
Abstract
Drought is the major environmental stress that adversely affects crop productivity in the Mediterranean region. Adopting water saving strategies, such as deficit irrigation or even no irrigation (rain-fed) and using drought-tolerant genotypes and/or landraces may represent effective tools to save water without substantial reduction of yield. An experiment was conducted in two consecutive growing seasons (2013 and 2014), to assess soil water content and matric potential of soil, physiological parameters, growth, yield and fruit quality of two Italian long-storage tomato landraces: " Locale di Salina 6 " (LS; 2013 and 2014) and " Piennolo del Vesuvio " (PV; 2014) under rain-fed (RF) and full irrigation (FI) conditions. Leaf water potential, CO 2 assimilation, stomatal conductance, photosynthetic efficiency and growth were moderately impaired under rain-fed conditions, while intrinsic water use efficiency slightly increased. The marketable yield of LS in both growing seasons, and PV in 2014 under RF conditions was slightly reduced (by 6%) as compared with the FI treatment, indicating a drought tolerance of both landraces. In the 2014 experiment, the marketable yield was significantly higher by 55% in PV than in LS landrace. When averaged over landraces, the fruit quality traits in particular fruit dry matter, total soluble solids and total ascorbic acid contents increased by 21, 33 and 55%, respectively under RF compared to FI. The results can play an important role in selecting tolerant genotypes for use under limited water supply in order to save water and improve fruit quality without affecting the crop productivity.
... Within tomato, most drought-resilient genotypes have been described among local landraces in the Mediterranean basin, due to their selection over centuries under Mediterranean summer conditions (Bota et al., 2014;Guida et al., 2017;Ochogavía et al., 2011;Patanè et al., 2016). Among those, several long shelf-life (LSL) landraces have improved drought tolerance as compared to modern genotypes, and some of their adaptive mechanisms allowing to increase WUE have already been described (Conesa et al., 2020;Fullana-Pericàs et al., 2019;Galmés et al., 2013Galmés et al., , 2011Guida et al., 2017;Tranchida-Lombardo et al., 2018). ...
... Within tomato, most drought-resilient genotypes have been described among local landraces in the Mediterranean basin, due to their selection over centuries under Mediterranean summer conditions (Bota et al., 2014;Guida et al., 2017;Ochogavía et al., 2011;Patanè et al., 2016). Among those, several long shelf-life (LSL) landraces have improved drought tolerance as compared to modern genotypes, and some of their adaptive mechanisms allowing to increase WUE have already been described (Conesa et al., 2020;Fullana-Pericàs et al., 2019;Galmés et al., 2013Galmés et al., , 2011Guida et al., 2017;Tranchida-Lombardo et al., 2018). The LSL phenotype, characterized by an extended fruit post-harvest conservation, exists in several West-Mediterranean landraces like the 'de Ramellet' tomato from the Balearic Islands (Bota et al., 2014;Conesa et al., 2014), the 'de Penjar' tomato from the Eastern Iberian Peninsula (Casals et al., 2012), and in some Italian (Sacco et al., 2017;Sinesio et al., 2007) and Greek landraces (Terzopoulos and Bebeli, 2010) (extended review of LSL landraces distribution and traits can be found in Conesa et al., 2020). ...
... The differences in physiologic parameters between CON and LSL (Table 1) agree with the results reported in previous studies comparing drought adapted LSL genotypes with commercial and non-droughtadapted genotypes, denoting a different physiologic behavior between those groups (Fullana-Pericàs et al., 2019Galmés et al., 2013Galmés et al., , 2011Giorio et al., 2018;Guida et al., 2017;Landi et al., 2017;Patanè et al., 2016). In this study, we show that these contrasting performance was also observed at whole-plant level, with differences between CON and LSL in NDVI and CPA regardless of the treatment (Table 1). ...
Field high-throughput phenotyping (HTPP) studies are highly needed to study water use efficiency (WUE), stress tolerance capacities, yield and quality in tomato to improve crop breeding strategies and adapt them to the climatic change scenario. In this study, UAV remote sensing is tested by comparison with leaf-level physiologic and agronomic measurements in a collection including 91 tomato genotypes. These genotypes include long shelf-life (LSL) and non-LSL (CON) Mediterranean landraces, cultivated under well-watered (WW, covering 100% crop evapotranspiration demands) and water deficit (WD, irrigation stopped one month after plantlet transplantation to field) conditions. Aerial remote sensing (including multispectral imaging), leaf gas-exchange, leaf carbon isotope composition (δ13C), fruit production and quality measurements, including total soluble solids and acidity, were performed. Differences between CON and LSL genotypes were observed in leaf-level physiologic and remote sensing measurements under both WW and WD conditions, while for agronomic measurements differences were only found for quality traits under WW conditions. Significant relationships were detected between remote sensing and leaf-level physiologic and agronomic measurements when considering all genotypes and treatments. However, different regressions were described for CON and LSL genotypes, mainly due their different physiologic behavior and response to WD. For instance, for the same NDVI value LSL genotypes showed near 30% lower AN and half gs than CON, and therefore higher intrinsic water use efficiency (WUEi). Also, tomato fruit quality was approached through remote sensing measurements, being correlated with multispectral indices. In conclusion, this study shows how remote sensing can help to optimize tomato physiologic and agronomic phenotyping processes. However, it also points out that the inclusion of genotypes with a different water use efficiency behavior and response to WD lead to a large scattering in the relationships between remote sensing and physiologic and agronomic traits and prevents to obtention of reliable models.
... Diverse drought experiments including landraces from Sicily and Campania denoted the lack of A N and g s differences among accessions, irrespective of the severity of the stress (Patanè et al., 2016;Guida et al., 2017;Giorio et al., 2018). Moreover, A N , g s and WUEi values under drought were close to those reported for 'de Ramellet' (Galmés et al., 2011) and, similarly, the A N to g s relationship indicated a saturation of A N and thus, a disproportionate, suboptimal water consumption under nonstressing conditions (Guida et al., 2017;Giorio et al., 2018). ...
... Diverse drought experiments including landraces from Sicily and Campania denoted the lack of A N and g s differences among accessions, irrespective of the severity of the stress (Patanè et al., 2016;Guida et al., 2017;Giorio et al., 2018). Moreover, A N , g s and WUEi values under drought were close to those reported for 'de Ramellet' (Galmés et al., 2011) and, similarly, the A N to g s relationship indicated a saturation of A N and thus, a disproportionate, suboptimal water consumption under nonstressing conditions (Guida et al., 2017;Giorio et al., 2018). Overall, despite maximum A N and g s varied considerably among Mediterranean LSL landraces and studies, WUEi under stress was grossly similar across landraces, with values at low g s (i.e., 0.15-0.30 ...
... Overall, despite maximum A N and g s varied considerably among Mediterranean LSL landraces and studies, WUEi under stress was grossly similar across landraces, with values at low g s (i.e., 0.15-0.30 mol m −2 s −1 ) close to 90-110 µmol mol −1 in "de Ramellet" (Galmés et al., 2011), Sicilian landraces (Guida et al., 2017;Giorio et al., 2018) and "Vesuviano" (Guida et al., 2017). ...
The Mediterranean long shelf-life (LSL) tomatoes are a group of landraces with a fruit remaining sound up to 6–12 months after harvest. Most have been selected under semi-arid Mediterranean summer conditions with poor irrigation or rain-fed and thus, are drought tolerant. Besides the convergence in the latter traits, local selection criteria have been very variable, leading to a wide variation in fruit morphology and quality traits. The different soil characteristics and agricultural management techniques across the Mediterranean denote also a wide range of plant adaptive traits to different conditions. Despite the notorious traits for fruit quality and environment adaptation, the LSL landraces have been poorly exploited in tomato breeding programs, which rely basically on wild tomato species. In this review, we describe most of the information currently available for Mediterranean LSL landraces in order to highlight the importance of this genetic resource. We focus on the origin and diversity, the main selective traits, and the determinants of the extended fruit shelf-life and the drought tolerance. Altogether, the Mediterranean LSL landraces are a very valuable heritage to be revalued, since constitutes an alternative source to improve fruit quality and shelf-life in tomato, and to breed for more resilient cultivars under the predicted climate change conditions.
... To achieve a certain amount of water savings, RDI method is considered as an efficient way, either in a predetermined developmental stage or throughout the whole production season, without decreasing plant yield significantly. Water-saving irrigation strategies and their effects on yield and quality in tomato have been studied by many researchers. It has been reported that there has been a slight decrease in fruit yield but an improvement of fruit quality when water is inadequate (Cantore et al., 2016;Djurovic et al., 2016;Guida et al., 2017). It has also been reported that increasing the amount of irrigation water increases fruit yield, but reduces the amount of Brix, lycopene, total polyphenol significantly. ...
... Full irrigation treatments resulted in a lower organic acid content and higher total antioxidant activity than deficit irrigation (Djurovic et al., 2016). Guida et al. (2017), reported that DM, TSS contents and total AA improved under limited water conditions. Nangare et al. (2016), concluded that the greatest advantage of the limited watering is the improvement of total SS, AA, acidity and lycopene, although the fruit size is affected adversely. ...
... The highest amount of AA in tomatoes was reported as 23.67 mg 100 g-1 (Ozbahce ve Padem, 2007). According to Guida et al. (2017), Tari and Sapmaz (2017) and Nahar and Gretzmacher (2002), citric acid content increased significantly under water stress and quality enhanced. ...
... In this regard, the Mediterranean basin has been considered a secondary center of diversification for the tomato crop (Bai and Lindhout, 2007;Lin et al., 2014;Miller and Tanksley, 1990). The diverse cultivation practices and selection criteria in each particular region gave rise to landraces adapted to local conditions and responding to local consumption habits (Bota et al., 2014;Casals et al., 2011; partially attributed to morphological and physiological adaptations, but also to biochemical traits (Galmés et al., 2013(Galmés et al., , 2011Guida et al., 2017;Riccardi et al., 2016). ...
... Taken into consideration the trade-off between WUE or δ 13 C and yield, the high δ 13 C and lower g s of LSL landraces may reflect an adaptation to severe water stress (Tardieu, 2011). Most LSL landraces studied are original from the Mediterranean basin, traditionally selected under rain-fed conditions leading to severe stress during the Mediterranean summer (Bota et al., 2014;Guida et al., 2017). On the contrary, modern LSL were included in the most Table 3 Leaf, yield and fruit quality traits in the different fruit and cultivar types under well-watered (WW) and water deficit (WD) conditions. ...
... These results highlight the potential of landraces, and specifically LSL, to be included in breeding programs to optimize yield and fruit quality under severe water deficit. The yield recorded for the different fruit and cultivar types is in accordance with previous studies (Bota et al., 2014;Di Gioia et al., 2010;Eshed and Zamir, 1994;Guida et al., 2017;Makkouk et al., 1979). However, due to the large diversity surveyed, some genotypes were poorly adapted to the specific growing conditions of the present study (open-field, high temperature, lack of pruning schedules) even under WW conditions (Fig. 1). ...
The predicted climate change conditions are forcing crop improvement researchers to find drought tolerant genotypes. The aim of this experiment was to screen a large tomato (Solanum lycopersicum L.) collection cultivated under well-watered and water deficit conditions, in order to identify those genotypes with the best performance under water shortage. Thus, 165 tomato genotypes including different cultivars (landraces and modern genotypes) and fruit types (processing, big size, long shelf-life and cherry) were grown in open field under two different cultivation regimes: well-watered (WW, covering 100% crop evapotranspiration demands) and water deficit (WD, irrigation stopped one month after field transplantation). Several leaf-level traits, yield and fruit quality were measured. Large variability was found under WW, with 20-fold variations in yield among genotypes. No differences in yield or fruit quality traits were found between modern genotypes and landraces, while differences in these parameters were observed based on the fruit type. Water deficit affected the observed variability, with a general decrease of yield and increases of fruit quality. Cluster analysis based on fruit traits placed several landraces in the same cluster that the most productive modern genotypes, irrespective of the water treatment. Variable responses to WD were observed, depending on the fruit or cultivar type. Carbon isotope composition was positively correlated with leaf nitrogen content, and determined the yield limit under both treatments. The results of this study highlight the potential of landraces for minimizing yield reduction under WD and increasing fruit quality, having similar or even better performance as compared to modern improved genotypes.
... The deep soil is characterized by high fertility. The fields used in this study developed on volcanic material and showed a loam texture formed by 40.9% sand, 32.8% silt and 26.3% clay (Guida et al., 2017). ...
... A critical mechanism conferring drought tolerance in plants is ROS detoxification (Gill and Tuteja, 2010;Krannich et al., 2015), but differences between commercial cultivars and local landraces in the involvement and efficiency of this process remain unclear. During centuries, in the Mediterranean area the farmers efforts generated many tomato landraces presenting different phenotypes, which generally had been selected for their tolerance to drought (Patan e et al., 2016;Guida et al., 2017); thus, 4 different long-storage tomato landraces of Southern Italy (CRO, LUC, GB, LS) were chosen and compared to a widely utilized processing cultivar (RED). ...
... Downstream the ROS scavenging system, G6PDH activity would represent the major source of reduced NADPH requested in the ascorbate-glutathione cycle (Esposito, 2016). It is worth noting that the specific involvement of G6PDH in stress response has been suggested: the non-catalytic isoform (encoded by G6PD4 in Arabidopsis e Wakao and Benning, 2005) can form heterodimers with chloroplastic G6PDH1 monomers, thus being able to cross the peroxisomal envelope, and create a machinery to support the increased request for reductants to ROS scavenging upon abiotic stress in these organelles (Meyer et al., 2011;H€ olscher et al., 2014). Gharsallah et al. (2016) showed a similar induction of CAT and APX activity, and proline content as well, in different tomato genotypes subjected to salt stress, further validating the pivotal role of these enzymes in oxidative stress response. ...
The involvement and the efficiency of the antioxidants scavenging system upon drought were examined by comparing traditional tomato landraces with respect to an industrial commercial genotype (Red Setter); for the first time, comprehensive analyses of physiological, biochemical and molecular parameters were investigated directly under real field conditions, in a typical agricultural environment of Southern Italy.
The characterization of the responses upon drought evidenced peculiar changes in stomatal conductance, ascorbate peroxidase and catalase activities and expression in drought tolerant tomato landraces, with respect to the industrial genotype.
An in silico analysis (promoter and co-expression study) coupled to a phylogenetic investigation of selected enzymes was performed, reinforcing the hypothesis of a basal activation of ROS scavenging machinery in the Mediterranean landraces.
Thus our data suggest a constitutive increase in the expression and activities of specific enzymes involved in ROS detoxification that can play a pivotal role in the drought response shown by tomato landraces.
Therefore, traditional landraces could represent an important source of useful genetic variability for the improvement of commercial varieties; their ROS detoxifying capabilities denote peculiar aspects worth being explored to better describe their specific stress tolerance.
... Our results indicate that plant productivity response to irrigation in long shelf-life tomatoes is genotypic-specific, as also revealed by the different irrigation water use efficiency (IWUE) corresponding to tomato cultivars. A large difference in fruit yield was also reported in literature between two landraces of long shelf-life tomatoes, cultivated under full irrigation and rainfed conditions [19], which suggests the feasibility to screen within the genetic resources and select for individual genotypes with high yield potential under restricted soil water availability. ...
... Repeated cycles of dehydration and rehydration in REW, besides promoting fruit yield, contributed to maintain high levels of polyphenols in fruits, whilst high rates of irrigation adversely affected the levels of these metabolites, as well as those of flavonoids. In general, the application of water stress has been reported to trigger the synthesis of antioxidant compounds including polyphenols, in vegetables, and the imposition of water stress during cultivation has been proposed as a valuable tool for producing high quality vegetables [19,[27][28][29][30]. A wide literature on tomato supports the results of the present study [4,5,10]. ...
The Mediterranean long shelf-life tomato (or long storage tomato) is a plant traditionally cultivated under no irrigation in the Southern regions of Italy, whose fruits have typical high sensory and nutritional quality. However, yield levels are kept low under current cultivation conditions. In this study, the effects of repeated cycles of drying and rehydration on crop productivity and nutritional quality of fruits in terms of polyphenols and carotenoids content were assessed in long shelf-life tomatoes cultivated in a typical semi-arid area of Southern Italy. The three local Sicilian landraces ‘Custonaci’, ‘Salina’ and ‘Vulcano’, and the commercial tomato hybrid ‘Faino’ (control) were submitted to three irrigation treatments: DRY (no irrigation); IRR (long-season full irrigation); REW (drought/rewatering cycles). Total 450, 4710, and 1849 m3 ha−1, were distributed in DRY, IRR, and REW, respectively. At harvest, fruit yield, polyphenols (as total, flavonoids, and hydroxycinnamoyl quinic acids-HCQA), and carotenoids contents (lycopene and β-carotene) were measured. All cultivars benefitted from very limited irrigation in REW, raising their productivity (up to +147% in ‘Vulcano’) with respect to that of plants overstressed in DRY. Irrigation water use efficiency in REW was higher than that in IRR. Water shortage in REW led to a polyphenols content of fruits that was slightly lower (171.1 μg g−1) than that in DRY, but higher than that in IRR (116.8 μg g−1). All local landraces had greater contents (>160 μg g−1) than control (113.0 μg g−1). Under REW and DRY, the two landraces ‘Salina’ and ‘Vulcano’ produced fruits with the same polyphenols and flavonoids contents. Overall, the two water stressed treatments (DRY and REW) did not differ for HCQA content (>66 μg g−1), which was significantly higher than that in the irrigated plots (
... Nevertheless, the extent of decrease in stomatal conductance depends on the growing period when the water deficiency occurred; at 7 days after anthesis of maize cultivars stomatal conductance decreased by 35% on average but at 21 days after anthesis this decrease was significantly larger (74%) under water deficiency than in well-watered cultivars [100]. In the case of tomatoes grown under non-irrigated conditions, stomatal conductance decreases from 14 to 73% depending on the weather and variety in comparison with the well-watered plants [3,32,87,101] (Table 3). Table 3. Physiological traits related to water use and photosynthesis for vegetable crops under optimal water supply (OW) and water stress (WS) conditions. ...
... Nevertheless, the extent of decrease in stomatal conductance depends on the growing period when the water deficiency occurred; at 7 days after anthesis of maize cultivars stomatal conductance decreased by 35% on average but at 21 days after anthesis this decrease was significantly larger (74%) under water deficiency than in well-watered cultivars [100]. In the case of tomatoes grown under non-irrigated conditions, stomatal conductance decreases from 14 to 73% depending on the weather and variety in comparison with the well-watered plants [3,32,87,101] ( Table 3). * SPAD = relative chlorophyll content of leaves; NDVI = normalized differential vegetation index. ...
The frequency of drought periods influences the yield potential of crops under field conditions. The change in morphology and anatomy of plants has been tested during drought stress under controlled conditions but the change in physiological processes has not been adequately studied in separate studies but needs to be reviewed collectively. This review presents the responses of green peas, snap beans, tomatoes and sweet corn to water stress based on their stomatal behaviour, canopy temperature, chlorophyll fluorescence and the chlorophyll content of leaves. These stress markers can be used for screening the drought tolerance of genotypes, the irrigation schedules or prediction of yield.
... It is clear that WS induced a negative effect on leaf biomass and fruit ripening, as confirmed by the reduction of leaf DW and the alteration of fruit-ripening processes. Our results are not consistent with those by other authors [38][39][40] but are in accordance with Khan et al. [41]. The differences observed in the WS sensitivity may be due to the severity of drought. ...
... In WS_P + fruits, a significant increase of total phenols was observed, suggesting that they contribute positively to the antioxidant activity of the tomato water-soluble fraction by reducing the levels of free radicals due to WS (as confirmed by the increase of ORAC and HORAC levels). This response can be considered an adaptive mechanism to water stress that promotes the de novo synthesis of these metabolites [40]. At the end of the experiment, the content of carbohydrates showed a similar trend. ...
Tomatoes, the most cultivated vegetables worldwide, require large amounts of water and are adversely affected by water stress. Solanum lycopersicum L., cv. Micro-Tom was used to assess the effects of β-(1,3)-glucan (paramylon) purified from the microalga Euglena gracilis on drought resistance and fruit quality profile. Plants were grown in an aeroponic system under three cultivation conditions: optimal water regimen, water scarcity regimen, and water scarcity regimen coupled with a root treatment with paramylon. Eco–physiological, physicochemical and quality parameters were monitored and compared throughout the lifecycle of the plants. Drought stress caused only a transient effect on the eco–physiological parameters of paramylon-treated plants, whereas physicochemical and biochemical parameters underwent significant variations. In particular, the fruits of paramylon-treated plants reached the first ripening stage two weeks before untreated plants grown under the optimal water regime, while the fruits of stressed untreated plants did not ripe beyond category II. Moreover, antioxidant compounds (carotenoids, phenolic acid, and vitamins) of fruits from treated plants underwent a two-fold increase with respect to untreated plants, as well as soluble carbohydrates (glucose, fructose, and sucrose). These results show that paramylon increases plant resistance to drought and highly improves the quality profile of the fruits with respect to untreated plants grown under drought stress.
... For MAL, CITR, and TAC, our results were very similar to those of Migliori et al. [35]; Contrarily, the same authors detected higher GLU, FRU, and SS contents in comparison to this research. These comparisons are very notable because they concern the same "Vesuviano" tomato biotype (PV-10 ISCI); thus, the differences in concentrations were solely due to extrinsic and environmental factors, such as weather trends during ripening, irrigation regimes, and fertilization practices [49][50][51][52]. Moreover, the amounts of SS and CITR in the fresh fruit were in agreement with results of Fratianni et al. [29] and Ercolano et al. [53], who analyzed other "Vesuviano" biotypes. ...
“Vesuviano” or “piennolo” tomato is among the most famous Italian small tomato landraces and is cultivated on the slopes of Vesuvio volcano (Southern Italy). The “piennolo” tomato is an interesting case with regard to its potential sustainability, as it is traditionally grown in water-deficit conditions with a low fertilizer input. Fruits with a high firmness and a thick skin can be stored for 3–4 months at room temperature (“long shelf-life” or LSL tomato) without postharvest fungicide applications. The aim of this research was to study the retention, changes in quality, and nutritional traits of “Vesuviano” tomatoes over 120 days of “natural” storage. The dry matter, soluble sugar, organic acids, volatile compounds, and carotenoid contents were evaluated at harvesting and in fruits
stored for 40, 80, and 120 days. Slight decreases in dry matter content, soluble sugars, and sweetness index were found, while the organic acids levels remained relatively stable. Moreover, interesting increases in the concentrations of certain flavor volatiles, alcohols, aldehydes, and terpenes were detected. Regarding carotenoids, the total lycopene levels exhibited a 1.5-fold increase from harvest to 120 days. The unchanged lycopene cis-isomer levels and the �-carotene/total lycopene ratio is characteristic of relatively stable isomerization activity and indicated an optimal ripening pattern up until the end of the “natural” storage period. These results, which demonstrate good overall quality retention of this LSL tomato, represent a well-grounded reason to enhance the cultivation and marketing of this genetic resource, the fruits of which can be appreciated by consumers during the winter–early spring, when high-quality fresh tomatoes are not available on the markets.
... To cope with drought stress, plants have developed several defensive mechanisms, which include changes in root architecture; more robust root systems; the production of epidermal wax; the modulation of stomatal conductance to reduce transpiration; the production of osmolytes; scavenging reactive oxygen species (ROS); and the mobilization of stress-related hormones [5][6][7]. Understanding these mechanisms of drought tolerance at the morphological, physiological, biochemical, and molecular levels is critical for crop improvement. ...
Grafting using suitable rootstocks mitigates the adverse effects caused by environmental stresses such as water deficit in the tomato crop. Solanum pennellii and Solanum peruvianum, the wild relatives of tomato, are used as rootstocks due to their tolerance to water deficit and soil-borne diseases. This study focused on evaluating physiological and biochemical responses of tomato plants grafted onto S. pennellii and S. peruvianum rootstocks during water deficit. The commercial tomato cultivar ‘HM 1823′ (HM) either self-grafted (HM/HM) or grafted onto S. pennellii (HM/PN), S. peruvianum (HM/PR), and ‘Multifort’ (HM/MU) rootstocks were subjected to water-deficit stress by withholding irrigation for eight days. The performance of the grafted plants under water deficit was evaluated using physiological and biochemical parameters in vegetative tissues of the grafted plants. Plants grafted using S. pennellii (PN) and S. peruvianum (PR) rootstocks showed higher values of water potential (Ѱw), relative water content (RWC), net photosynthetic rate (A), and leaf water use efficiencies (WUE) compared to HM, HM/HM, and HM/MU. Plants grafted onto tomato wild relatives showed the lowest malondialdehyde (MDA) and proline content. This study demonstrated that the rootstocks of wild tomato relatives reduced the effect of water deficit to a greater extent through better physiological, metabolic, and biochemical adjustments than self-grafting plants.
... They concluded that selecting proper cultivars and irrigation strategies on suitable soils can sustain current production levels under changing climatic conditions. In some instances, long-storage tomato landraces have been found that can adapt well even to rainfed conditions, as reported by Guida et al. (2017). Besides the use of well-adapted tomato varieties, literature includes many studies on improved irrigation management with the purpose of mitigating water scarcity. ...
Intensification of low-tech agricultural production is required in the Greater Giyani Municipality (Limpopo province, South Africa) to respond to changing climatic conditions, water scarcity and increased food demand of the local market. Two years of field experiments were conducted on two typical small-scale farms under real-world conditions. The objective was to test the response of locally available tomato (Lycopersicon esculentum Mill.) cultivars (Rodade, STAR 9006, Commander, HTX 14 and MFH) to two different irrigation strategies (full irrigation FI and deficit irrigation DI). While results showed high tomato yield variability (ranging between 9.2 t ha⁻¹ and 59.7 t ha⁻¹) depending on the farms, environmental conditions (heatwaves, diseases) and irrigation management, STAR 9006 appeared to be the best performing cultivar and HTX 14 the worst. Seasonal evapotranspiration under FI was between 400 and 620 mm depending on the length of the season and harvesting time. Crop water productivity was generally higher for DI than FI treatments. Deficit irrigation appeared to be feasible to reduce water use for some cultivars (eg cv. STAR 9006), however, an economic analysis should be conducted at specific sites/farms to determine the impacts of DI on farmers’ income as some yield losses can be expected during drought years.
... Studies were carried out extensively on identifying and exploiting the target traits valuable for improving WUE to facilitate breeding drought-tolerance and high-efficient water use cultivars (Dunn et al., 2019;Condon, 2020). Traditionally genotypes or cultivars were grown under non-irrigated conditions in Mediterranean environments and selected based on their adaptation to water deficit conditions (Galmés et al., 2011;Patanè et al., 2016;Guida et al., 2017). The selection of landraces other than those of drought-tolerant genotypes or cultivars represents an interesting genetic source in breeding and/or biotechnological improvements for drought tolerance and high WUE (Galmés et al., 2011(Galmés et al., , 2013Siracusa et al., 2012;Medrano et al., 2015). ...
Water use efficiency (WUE), defined as the ratio of plant carbon gain to water use in various spatio-temporal scales, is a complex indicator of physiological, agronomic, and engineering processes, as well as management practices. Improving WUE at different scales is an important pathway to combat the global water shortage and ensure food supply, which requires both understanding the physiological mechanisms of crop responding and adapting to water deficit, and innovating field water management technologies. We reviewed advances and perspectives in the research field related to improving WUE at different scales and discussed the key obstacles and possible solutions in practice. A water-saving, quality-improving, high-efficient water use strategy was proposed and an integrative management approach making use of diverse advanced WUE improving technologies was constructed. Both the water use strategy and integrative approach were developed based on physiological mechanisms of crop responding to water deficit, crop life water requirements, precision irrigation water management according to real-time monitoring of crop responses to water deficit, as well as crop water-yield-quality models. The review was expected to provide a reference for researchers in the water management communities and boost sustainable development of water-saving agriculture in water shortage areas.
... The cherry-type 'Máriapócs' always had a low yield; nevertheless, it is recommended to grow as it is tasteful, diversifies the assortment and its ripening timeline is the longest if suckers with clusters are not removed. These results suggest that with the right timing, landraces can perform similarly or even better than commercial varieties, in concordance with other studies [19,50]. Although the different experimental design and environmental parameters do not allow us to analyze the results of the plastic tunnel and open field together, it was shown that outcomes for both methods are similar with some key differences, e.g., the potential yield of indeterminate tomato gene bank accessions can be higher under protected management. ...
Landraces are generally neglected by industrialized agriculture, regardless of their potential to provide valuable genetic material for breeding and to diversifying the available assortment for producers and markets. They may also excel in certain plant protection issues with possible resistance or tolerance to plant pathogens. This is the first report on the disease susceptibility traits of Hungarian on certain indeterminate and determinate tomato gene bank accessions under on-farm organic conditions. For this, a three-year on-farm experiment was conducted in two management systems, open-field and protected. Yield and disease symptoms data obtained from ten tomato landraces were compared to commercial varieties. The incidence and severity of three important diseases (caused by late blight ‘Phytophthora infestans’, early blight ‘Alternaria solani’ and Septoria leafspot ‘Septoria lycopersici’), as well as yield, were recorded and assessed. According to these results, there were no significant difference between landraces and control varieties (San Marzano, Kecskeméti 549) regarding the studied parameters, and year was a determinant factor in the occurrence and severity of the infection of the studied diseases. In 2016, rainy, humid weather induced a severe late blight infection, causing serious damage to the open field, while the weather in 2015 and 2017 was favorable for tomato production and our measurements. There were some differences within and between landraces in terms of susceptibility. The investigation revealed that certain accessions can be highly recommended, e.g., the indeterminate ‘Fadd’ (RCAT030275) and ‘Mátrafüred’ (RCAT057656) had suitably high yields with significantly lower susceptibility to late blight, and the determinate ‘Szentlőrinckáta’ (RCAT078726) with high yield as well as tolerance to early blight is also recommendable, but it is sensitive to late blight under an adverse environment. This study suggests that landraces are competitive with the studied commercial varieties under organic production systems. Considering yield and the prevention of the major diseases of tomato, the studied tomato gene bank accessions are recommended for organic field and protected management systems.
... It is generally believed that water deficit reduces the number of fruits (Coyagocruz et al., 2019;Favati et al., 2009). However, some studies pointed out the variations in irrigation amount or methods under partial root-zone drying (Zegbe et al., 2004) or field conditions (Guida et al., 2017) did not affect the tomato fruit number, which supports our results. Abortion of flower and fruit is related to the limit of sink strength, and reducing the inhibition of sink strength on photosynthesis is beneficial to tomato fruit setting (Ruan et al., 2012). ...
To address the twin issues of food and nutrition security, the focus of agricultural production should be shifted from biomass productivity to nutritional gains. The objectives of this study were to evaluate the impact of conversion from furrow to drip irrigation on the yield components, water productivity (WP), nutritional yield (NY) and nutritional water productivity (NWP) of tomato during two consecutive growth cycles (2017-2018) in a greenhouse in the arid area of Northwest China. Results showed that the environment under drip irrigation was more beneficial to the accumulation of phytochemicals and the formation of total antioxidant activity in tomato fruits, which also significantly increased the NWP. However, the notable decline in single fruit fresh weight reducing the tomato yield significantly under drip irrigation in summer, while the WP and NY were similar to furrow irrigation. This indicated that the NY of tomato was mainly determined by the fruit yield, while the NWP was strongly affected by the mass concentration of nutrients. In contrast, no difference was found in the single fruit fresh weight and tomato yield between drip and furrow irrigation in winter, which related to the similar environmental conditions, while the WP and NY were significantly higher under drip irrigation. In summary, the potential and water use efficiency in nutrient production of tomato were enhanced under drip irrigation, and the improvement of fruit quality can offset the negative effect of yield reduction. Therefore, drip irrigation can achieve a good balance between the high yield and superior quality of tomato fruits, meanwhile reducing the pressure on the environment caused by horticultural production. We propose that the drip irrigation should be employed in the greenhouse in arid areas for tomato production, and the concepts of NY and NWP can be further applied to other horticultural crops with high nutritional value.
... One part of accessions displayed better flavour in water stressed fruits while the other part manifested deterioration. Taking into account the high correlation found between tomato sensory traits and organoleptic compositions (Causse, Damidaux & Rousselle 2007;Tandon et al. 2003) we could say our results did not fully support the suggestion given by other authors that water deficit improves fruit quality (Guida et al. 2017;Chen et al. 2013). In our investigation under limited water supply the sensory characteristics of tomato fruits mainly depended on the genotype (Tables 2, 3, 5). ...
The effect of water deficit on sensory characteristics of tomato (Solanum lycopersicon L.) was investigated. A field experiment was carried out during 2016-2017 period under the hot summer conditions in Bulgaria. Twenty four Bulgarian tomato accessions representing three types-indeterminate, determinate for processing and determinate for fresh consumption-were harvested. Optimum and 50% reduced watering regimes were applied using a drip irrigation system. Temperatures over 35ºС during the vegetation were recorded in 26% of the days of the first experimental year and 40% of the days of the second one. The sensory analysis of the tomato fruits was performed by trained panelists on the traits: appearance, shape, external colour, internal colour, aroma, peel tenderness, visible fibre, sourness, sweetness, texture and overall taste. Negative effects of the deficit irrigation were observed on the appearance, shape and total sensory evaluation of tomato fruits regardless of the tomato type. Negative effects were also recorded on the texture of determinate tomato for processing and peel tenderness of determinate tomato for fresh consumption. The sweetness was better expressed in tomatoes grown under water deficit in all studied genotypes. Reduced irrigation did not result in aroma, external colour and visible fibre. Two-way analysis of variance revealed a significant influence of genotype on the sensory traits in the range of 39.56-74.79% in indeterminate tomato accessions, 33.49-56.05% in determinate tomato for processing, 14.96-62.93% in determinate tomato for fresh consumption. Slight influence of the applied watering regime was established except for appearance, shape and sweetness. Indeterminate tomato accessions Rozovo sartse and BG 21 β, determinate accession for processing BG 2086 and determinate accession for fresh consumption Marti and BG 252 demonstrated the best sensory profile in both treatments of irrigation.
... One part of accessions displayed better flavour in water stressed fruits while the other part manifested deterioration. Taking into account the high correlation found between tomato sensory traits and organoleptic compositions (Causse, Damidaux & Rousselle 2007;Tandon et al. 2003) we could say our results did not fully support the suggestion given by other authors that water deficit improves fruit quality ( Guida et al. 2017;Chen et al. 2013). In our investigation under limited water supply the sensory characteristics of tomato fruits mainly depended on the genotype (Tables 2, 3, 5). ...
... The relative chlorophyll concentration in the leaves as SPAD value is associated with the crop's quality parameters (Martıńez et al., 2017). A number of studies investigated the effect of water supply on tomato crop quality (Guida et al., 2017;Agbna et al., 2017) but under these conditions, the knowledge concerning the effect of soil microorganisms on photosynthesis and their relationship with quality of tomato crop is incomplete. The aim of the study was to examine the effect of mycorrhizal and bacterial products on some traits related to photosynthesis and the fruit quality of processing tomato under water deficit conditions. ...
... Mediterranean tomato landraces have been traditionally cultivated under rain-fed water regimes, and selected over centuries for drought resistance and (long storage) over-winter consumption of fruits (Galm es et al. 2011(Galm es et al. , 2013Conesa et al. 2014), with high quality and nutritional properties (Siracusa et al. 2011). Several studies have focused on yield response under rain-fed conditions (Patan e et al. 2016;Guida et al. 2017) and the primary role played by diffusive conductance in photosynthetic limitations (Galm es et al. 2011(Galm es et al. , 2013Fullana-Peric as et al. 2016). ...
Mediterranean tomato landraces adapted to arid environments represent an option to counteract drought, and to address the complexity of responses to water deficit and recovery, which is a crucial component of plant adaptation mechanisms.
We investigated physiological, biochemical and molecular responses of two Mediterranean tomato landraces, “Locale di Salina” (Lc) and “Pizzutello di Sciacca” (Pz) under two dehydration periods and intermediate rehydration in greenhouse pot‐experiments.
Relationship between CO2 assimilation and stomatal conductance under severe water stress (gs < 0.05 mol m⁻² s⁻¹) indicated the occurrence of stomatal and non‐stomatal limitations of photosynthesis. Gas‐exchanges promptly recovered within 2‐3‐day re‐hydration. ABA and gs showed a strict exponential relationship. Both leaf ABA and proline peaked under severe water stress. Lc showed higher accumulation of ABA and higher induction of the expression of both NCED and P5CS genes than Pz. PARP increased during imposition of stress, mainly in Lc, and decreased under severe water stress.
The two landraces hardly differed in their physiological performance. Under severe water stress, stomatal conductance showed low sensitivity to ABA, which instead controlled stomatal closure under moderate water stress (gs > 0.15 mol m⁻² s⁻¹). The prompt recovery after re‐dehydration of both landraces confirmed their drought tolerant behaviour. Differences between the two landraces were instead observed at biochemical and molecular levels.
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... Investigating local accessions germplasm for these beneficial stress-related traits could be a sustainable strategy to provide food and valorise marginal lands with a view to counteract the future climate changes (Halford and Foyer, 2015). Interestingly, drought-tolerance traits have been found among Mediterranean tomato accessions, which are typically cultivated in limited water supply scenario (Galmés et al., 2013;Patanè et al., 2016;Guida et al., 2017). ...
Water deficit triggers a dynamic and integrated cross-talk between leaves and roots. Tolerant plants have developed several physiological and molecular mechanisms to establish new cell metabolism homeostasis, avoiding and/or escaping from permanent impairments triggered by drought. Two tomato genotypes (a Southern Italy landrace called Ciettaicale and the well-known commercial cultivar Moneymaker) were investigated at vegetative stage to assess leaf and root metabolic strategies under 20 days of water deficit. Physiological and metabolic changes, in terms of ABA, IAA, proline, soluble sugars and phenols contents, occurred in both tomato genotypes under water stress. Overall, our results pointed out the higher plasticity of Ciettaicale to manage plant water status under drought in order to preserve the source-sink relationships. This aim was achieved by maintaining a more efficient leaf photosystem II (PSII) photochemistry, as suggested by chlorophyll fluorescence parameters, associated with a major investment towards root growth and activity to improve water uptake. On the contrary, the higher accumulation of carbon compounds, resulting from reduced PSII photochemistry and enhanced starch reserve mobilization, in leaves and roots of Moneymaker under drought could play a key role in the osmotic adjustment, although causing a feedback disruption of the source-sink relations. This hypothesis was also supported by the different drought-induced redox unbalance, as suggested by H2O2 and MDA contents. This could affect both PSII photochemistry and root activity, leading to a major involvement of NPQ and antioxidant system in response to drought in Moneymaker than Ciettaicale.
... After 2 days of the water deficit imposition, during the physiologic evaluations, the substrate was submitted to a moderate matricidal potential (below -25 kPa) ( Figure 1). Guida et al. (2017), when submitting tomato plants to a water stress, observed that the soil matricidal potential below -28 kPa promotes a reduction in the stomatal conductance, affecting the crop yield. Analyzing the climatic conditions in the greenhouse, it was found that the average temperature was 23.4°C, which is close to the ideal temperature (18°-24°C), for the tomato crop, according to Duarte et al. (2011). ...
Water stress can affect the yield in tomato crops and, despite this, there are few types of research aiming to select tomato genotypes resistant to the water stress using physiological parameters. This experiment aimed to study the variables that are related to the gas exchanges and the efficiency in water use, in the selection of tomato genotypes tolerant to water stress. It was done in a greenhouse, measuring 7 x 21 m, in a randomized complete block design, with four replications (blocks), being five genotypes in the F2BC1 generation, which were previously obtained from an interspecific cross between Solanum pennellii versus S. lycopersicum and three check treatments, two susceptible [UFU-22 (pre-commercial line) and cultivar Santa Clara] and one resistant (S. pennellii). At the beginning of flowering, the plants were submitted to a water stress condition, through irrigation suspension. After that CO2 assimilation, internal CO2, stomatal conductance, transpiration, leaf temperature, instantaneous water use efficiency, intrinsic efficiency of water use, instantaneous carboxylation efficiency, chlorophyll a and b, and the potential leaf water (Ψf) were observed. Almost all variables that were analyzed, except CO2 assimilation and instantaneous carboxylation efficiency, demonstrated the superiority of the wild accession, S. pennellii, concerning the susceptible check treatments. The high photosynthetic rate and the low stomatal conductance and transpiration, presented by the UFU22/ F2BC1#2 population, allowed a better water use efficiency. Because of that, these physiological characteristics are promising in the selection of tomato genotypes tolerant to water stress.
Increasingly, consumers are paying attention to healthier food diets, “healthy” food attributes (such as “freshness”, “naturalness” and “nutritional value”), and the overall sustainability of production and processing methods. Other significant trends include a growing demand for regional and locally produced/supplied and less processed food. To meet these demands, food production and processing need to evolve to preserve the raw material and natural food properties while ensuring such sustenance is healthy, tasty, and sustainable. In parallel, it is necessary to understand the influence of consumers’ practices in maintaining the beneficial food attributes from purchasing to consumption. The whole supply chain must be resilient, fair, diverse, transparent, and economically balanced to make different food systems sustainable. This chapter focuses on the role of dynamic value chains using biodiverse, underutilised crops to improve food system resilience and deliver foods with good nutritional and health properties while ensuring low environmental impacts, and resilient ecosystem functions.
Tomato is a popular healthy fruit worldwide because it is rich in secondary metabolites such as vitamin C. Deficit irrigation (DI) can be applied to improve tomato fruit quality to a certain degree and save water consumption. However, the effects of DI on tomato quality are complex and affected by factors such as tomato variety and soil bulk density and texture. The objective of this paper is to use meta-analysis to 1) investigate the effects of DI on tomato quality variables and 2) study how soil texture, soil bulk density and three tomato varieties affect quality variables under DI compared to those under full irrigation. We collected 83 research papers from around the world and analyzed 2369 data pairs. Overall, DI increased the total soluble solids (12.44%), soluble sugar (11.23%), organic acids (6.58%), sugar/acid content ratio (14.56%), vitamin C (13.84%), lycopene (10.46%), color index (8.42%), red-green value (11.89%), shape index (3.25%) and firmness (12.09%) while decreasing β-carotene, lightness, hue angle and yellow-blue value by 11.11%, 1.77%, 3.42% and 4.26%, respectively. In addition, DI had no significant effects on tomato chroma (0.89% on average; 95% CI: -0.96% to 2.79%) or pH (0.13% on average; 95% CI: -0.26% to 0.52%). The results indicated that it would be better to apply deficit irrigation in fine and coarse soil, because most of the quality variables improved more in these soil textures than in medium soil. Soil with a bulk density of 1.2∼1.4 g cm⁻³ benefited taste quality, vitamin C and shape index. The quality of the three tomato varieties responded differently to water deficit conditions. Moreover, cherry tomato responded better to water deficit conditions than the other two tomato varieties; four quality variables improved the most in cherry tomato and two other variables were also improved. Our findings could help to obtain a better understanding of how fruit quality responds to DI in different soil textures, soil bulk densities and tomato varieties and to produce higher-quality tomatoes.
Fruit is important for human health and applying deficit irrigation (DI) in fruit production is a strategy to regulate fruit quality and support environmental sustainability. Responses of different fruit quality variables to DI have been widely documented and much progress has been made to understand the mechanisms of these responses. We review the effects of water shortage on fruit water accumulation considering water transport from the parent plant into the fruit determined by hydraulic properties of the pathway (including xylem water transport and transmembrane water transport regulated by aquaporins) and the driving force for water movement. We discuss water relations and solute metabolism that affect main fruit quality variables (e.g., size, flavour, nutrition and firmness) at the cellular level under water shortage. We also summarize the most recent advances in the understanding of responses of main fruit quality variables to water shortage, considering the effects of variety, the severity of water deficit imposed and the developmental stage of the fruit. We finally identify knowledge gaps and suggest avenues for future research. This review provides new insights into the stress physiology of fleshy fruit, which will be beneficial for the sustainable production of high-quality fruit under DI.
Effects of drought and salt stress on fruit quality in grafted plants, which salt and drought tolerance Mardin Kızıltepe (MK), Burdur Merkez (BM) and sensitive Kemer (K), Artvin Hopa (AH) as scion genotypes were grafted on the salt tolerance commercial eggplant as rootstocks (Köksal and Vista). This study was carried out in glasshouse where controlled temperature and humidity. For drought stress, plant-available water, 50% was consumed for irrigation. The salinity level determinated as 6 dS m-1 (EC) with NaCl. The end of the experiment, fruit dry weight (DW), fruit juice EC level, titratable acidity (TA), soluble solid content (SSC), vitamin C (Vit C) contents were investigated. These parameters values were increased with drought and salinity; however fruit pH level was decreased. In the grafted plants on Köksal and Vista rootstock, fruit juice EC level, soluble solid content and Vit C content increased under drought conditions compared to control plants. As a result, using of tolerance rootstock in grafting was found effectively improving of fruit quality under drought condition in eggplant.
Drought is one of the most serious threats to crop production all over the world and is likely to worsen with anticipated changes in the climate. Drought impairs normal growth, disturbs water relations and reduces water-use efficiency in plants. Plants, however, have a variety of physiological and biochemical responses at cellular and organism levels, making it a more complex phenomenon. Researchers have been trying to understand and dissect the mechanisms of plant tolerance to drought stress using various approaches. The present chapter describes the strategies used by plants to adapt to low water potential at physiological, biochemical and molecular levels. This chapter also describes the strategies involving genetic engineering used by breeders in order to obtain crop varieties with improved drought tolerance, some of which show great promise. Modern genomic and genetic approaches coupled with breeding methodologies are expected to more effectively identify the genes and metabolic pathways that confer drought tolerance in crops.
Drought is one of the most serious threats to crop production all over the world and is likely to worsen with anticipated changes in the climate. Drought impairs normal growth, disturbs water relations and reduces water-use efficiency in plants. Plants, however, have a variety of physiological and biochemical responses at cellular and organism levels, making it a more complex phenomenon. Researchers have been trying to understand and dissect the mechanisms of plant tolerance to drought stress using various approaches. The present chapter describes the strategies used by plants to adapt to low water potential at physiological, biochemical and molecular levels. This chapter also describes the strategies involving genetic engineering used by breeders in order to obtain crop varieties with improved drought tolerance, some of which show great promise. Modern genomic and genetic approaches coupled with breeding methodologies are expected to more effectively identify the genes and metabolic pathways that confer drought tolerance in crops.
Modern agriculture is faced with two tasks: (1) to produce enough food for a growing global population,and (2) to ensure satisfactory crop quality while using water resources efficiently. A study of the effectof kaolin on the yield, quality and water use efficiency of tomato (Lycopersicon esculentum Mill.), grownunder different irrigation regimes, is reported in the paper. The research was conducted in an open fieldwith carbonate chernozem soil, at Stara Pazova (40 km north of Belgrade, Serbia). It lasted for three years(2011, 2012, and 2013). The experimental setup was a two-factorial, completely random block system,with three replications. The first factor was the irrigation regime and the second the application of kaolin.Two irrigation treatments were studied: (a) full irrigation (F), covering 100% of ETc (crop evapotranspi-ration), and (b) deficit irrigation (D) at 50% of ETc. The kaolin treatments were: (a) control treatment,without kaolin (C) and treatment with a 5% suspension of kaolin (K).On average, the highest fresh tomato fruit yields were achieved under full irrigation, with kaolin (FK)(21.0 kg m−2). The FK treatment also resulted in the greatest dry weight of the fruits (1.1 kg m−2). Theaverage fruit weight was rather uniform and ranged from 71.7 g with DC to 75.4 g with DK. The averagesugar and lycopene content was quite uniform over the study period, while the irrigation regime hada significant effect on the average organic acid content and total antioxidant activity. Deficit irrigationtreatments resulted in a higher organic acid content and higher total antioxidant activity than full irriga-tion. The application of kaolin had a greater effect of the water use efficiency of tomato than the irrigationtreatment.
Favorable temperatures for tomato (Solanum lycopersicum L.) cultivation are between
25 and 30◦C during the day and 20◦C at night. Average global temperatures are increasing
by approximately 0.3◦C per decade. A 2–4◦C increase over the optimal (25◦C)
temperature adversely affects plant growth, flowering, gamete development, embryo
development, and seed germination; inhibits the ability of pollinated flowers to develop
into seeded fruit; inhibits fruit ripening; and reduces yield. Drought resulting from
insufficient rainfall and/or altered precipitation patterns is another important climatic
stress factor for tomato, often accompanied by relatively high temperature, in
which evapotranspiration is affected and photosynthetic kinetics and crop productivity
reduced. Application of genomics in tomato, to discover novel and high-throughput
genetic and molecular technologies as an indirect selection tool, provides the potential
for increasing efficiency of breeding by reducing the genotype × environment interaction,
facilitating efficient introgression of superior alleles from wild species into plants,
promoting gene-pyramiding control of quantitative traits, and enhancing development
of stress-tolerant, higher yielding varieties. Advances in genetics and genomics have
improved the understanding of structural and functional aspects of plant genomes. The
CBF/NHX1/DREB1 genes have been used successfully to engineer drought tolerance in
tomato. These genes are transcription factors implicated in tomato response to drought
and heat stress. There are few tomato varieties/species which can easily adapt to stress
tolerance as environmental conditions change. Some tomato varieties and wild species
are heat and drought tolerant. The focus of research is to use tools and techniques to
deliver global integration and overcome effects of environmental stresses on tomato.
Previous partial root-zone drying (PRD) experiments on tomato, carried out under controlled conditions, have occasionally shown significant positive results in terms of increased water-use efficiency and fruit quality. These results raised expectations for the transfer of PRD to commercial-scale tomato growing. However, PRD experiments in the open field are completely lacking for processing tomato varieties. An experiment was conducted, in two consecutive growing seasons, to assess the potential of PRD compared to deficit irrigation (DI) or full irrigation (FULL), on two varieties of processing tomato, using drip irrigation. Both the DI and PRD treatments delivered a 50% recovery of crop evapotranspiration (ETc), whereas the FULL treatment delivered 100% of ETc. Soil moisture measurements highlighted the difficulty in attaining the desired alternate wet and dry pattern in different parts of the root-zone prescribed by PRD, as well as the considerable water stress experienced under PRD or DI. On average, over the 2 years, marketable yields were significantly reduced, by 56% under DI and by 52% under PRD, compared to FULL irrigation.Yield decreases were caused by reductions in fruit fresh weight (FW), rather than in the number of fruit per plant. DI and PRD improved fruit quality in terms of total soluble solids contents (TSSC) as well as titratable acidity (TA) and juice pH, but not lycopene concentrations or fruit colour.Water-use efficiency (WUE), calculated as the ratio of marketable yield to actual evapotranspiration (ETa; calculated using the water balance) was not significantly different among treatments. However, when computed as the ratio of above-ground dry weight (biomass) to ETa, WUE was higher, on average, in the PRD (2.1 kg m-3) and DI (1.9 kg m-3) treatments than in the FULL treatment (1.4 kg m-3).
Additional index words. drainage water, irrigation, Lycopersicon esculentum, solids Abstract. Effects of deficit irrigation and irrigation with saline drainage water on processing tomato (Lycopersicon esculentum Mill, cv. UC82B) yields, fruit quality, and fruit tissue constituents were investigated in two field experiments. Deficit irrigation reduced fruit water accumulation and fresh fruit yield, but increased fruit soluble solids levels and' led to higher concentrations of hexoses, citric acid, and potassium. Irrigation with saline water had no effect on total fresh fruit yield or hexose concentration, but slightly reduced fruit water content, which contributed to increased inorganic ion concentrations. Fruit set and marketable soluble solids (marketable red fruit yield x percent soluble solids) were generally unaffected by either irrigation practice. Water deficit and salinity increased starch concentration during early fruit development, but, at maturity, concentrations were reduced to < 1%, regardless of treatment. Higher fruit acid concentrations resulted from water deficit irrigation and from irrigation with saline water relative to the control in one year out of two. These results support the contention that deficit irrigation and irrigation with saline drainage water may be feasible crop water management options for producing high quality field-grown processing tomatoes without major yield reductions. Appropriate long-term strategies are needed to deal with the potential hazards of periodic increases in soil salinity associated with use of saline drainage water for irrigation.
Limited water supply in the Mediterranean region is a major problem in irrigated agriculture. Grafting may enhance drought resistance, plant water use efficiency, and plant growth. An experiment was conducted in two consecutive growing seasons to determine yield, plant growth, fruit quality, leaf gas exchange, water relations, macroelements content in fruits and leaves, and water use efficiency of mini-watermelon plants [Citrullus lanatus (Thunb.) Matsum. and Nakai cv. Ingrid], either ungrafted or grafted onto the commercial rootstock 'PS 1313' (Cucurbita maxima Duchesne x Cucurbita moschata Duchesne), under open field conditions. Irrigation treatments were 1.0, 0.75, and 0.5 evapotranspiration rates. In both years (2006 and 2007), marketable yield decreased linearly in response to an increase in water stress. When averaged over year and irrigation rate, the total and marketable yields were higher by 115% and 61% in grafted than in ungrafted plants, respectively. The fruit quality parameters of grafted mini-watermelons such as fruit dry matter and total soluble solids content were similar in comparison with those of ungrafted plants, whereas titratable acidity, K, and Mg concentrations improved significantly. In both grafting combinations, yield water use efficiency (WUEy) increased under water stress conditions with higher WUE values recorded in grafted than ungrafted plants. The concentration of N, K, and Mg in leaves was higher by 7.4%, 25.6%, and 38.8%, respectively, in grafted than in ungrafted plants. The net assimilation of CO2, stomatal conductance, relative water content, leaf, and osmotic potential decreased under water stress conditions. The sensitivity to water stress was similar between grafted and ungrafted plants, and the higher marketable yield from grafted plants was mainly the result of an improvement in nutritional status and higher CO2 assimilation and water uptake from the soil.
Fruit soluble solids concentration (SSC) is an important quality factor for tomatoes (Lycopersicon esculentum Mill.) grown for processing. The use of drip irrigation often results in undesirably low SSC. The effects of late-season irrigation management on fruit yield and SSC was investigated in a series of drip-irrigated field trials in California from 2000-04. The effects of irrigation cutoff or deficit irrigation implemented 40 to 50 days preharvest (the period corresponding to the initiation of fruit ripening) were compared to a standard grower practice of irrigation cutoff 20 days preharvest. Irrigation cutoff 40 to 50 days preharvest increased SSC but resulted in substantial yield loss, with significantly reduced brix yield (Mg fruit solids ha -1). By contrast, deficit irrigation significantly increased SSC compared to the standard practice, with no significant loss of brix yield. In three commercial fields the effect of deficit irrigation on fruit SSC was investigated. Fruits were sampled on three dates: 1) 4 to 5 weeks preharvest, early-ripening, pink-stage fruit only, 2) about 1 week preharvest, both late-ripening, pink-stage fruit and early-ripening fruit now fully ripe, and 3) commercial harvest, composite of early- and late-maturing fruit. SSC increased in response to soil moisture stress induced by deficit irrigation, with late-maturing fruit as much as 1.6 °brix higher than fruit maturing before significant soil moisture stress. However, once a fruit reached the pink stage of maturity, its SSC was not affected by subsequent soil moisture stress. An additional five commercial field trials were conducted to compare growers' irrigation practices with greater degrees of deficit irrigation. In each field the grower's deficit irrigation regime was compared to a reduced treatment receiving 25% to 50% less water over the final 4 to 7 weeks before harvest. Across fields, applying 20% to 60% of reference evapotranspiration (ET o) over the fruit ripening period resulted in acceptable SSC without significant brix yield reduction. We conclude that deficit irrigation initiated during early fruit ripening provides a flexible tool for SSC management. Brix monitoring of earliest ripening fruit can help classify fields as to the severity of irrigation deficit required to reach desirable SSC at harvest.
Field experiments were conducted to examine the variability in the pattern of water use (ET), water use efficiency and fruit yield of field grown rainfed and irrigated tomato during the late (post-rainy) sowing season in a humid zone of Nigeria. The annual pattern of rainfall and rainfed potential production of crops showed that the dry (post) rainy season is characterized by water adequacy index (Ao), which was calculated from rainfall and ETo ranging from 0.01 -0.33 (Dec -March), The late sowing season falls within August-December (Ao < 0.34) ending in a terminal drought situation while the wet/rainy season falls season falls between March/April to July with an Ao ranging from 0.34 to 1.0. The mean seasonal values of SE, Tr, ETa were 37.6, 38.5, 73.8 and 25.1, 25.8, 53.2 mm for the respective rainfed and irrigated tomato. Mean seasonal soil water evaporation (SE) ranges from 37 and 11 mm. day -1 which constituted 5.6 and 14.4% of ETa for the respective rainfed and irrigated fields. Trends in the values of soil water evaporation for both rainfed and irrigated fields showed that greater SE was obtained under rainfed tomato, which also had lower crop transpiration. Evapotranspiration efficiencies (ET E 0.35, 0.18 & 0.20, 0.12 kg water per kg dry matter) and crop water use efficiencies (WUE; 0.012, 0.20 & 0.013, 0.09 kg water per kg dry matter) for biomass and fruit yields in the respective rainfed and irrigated tomato. Transpiration efficiencies (TR E) measured for biomass and fruit were 1.94 and 2.22; 1.91 and 2.17 kg water per kg dry matter. Relative water use (ETa/Eo) and drought index values for the respective rainfed and irrigated tomato were 1.08, 0.11 and 0.49, 0.11. Over rainfed tomato, plant biomass (root & shoot dry weights) and leaf area were enhanced by irrigation and the improved growth was accompanied by high fruit yield and WUE.
Favorable temperatures for tomato (Solanum lycopersicum L.) cultivation are between 25°C and 30°C during daytime and 20°C at night. Average global temperatures are increasing by approximately 0.3°C per decade. A 2-4°C increase over the optimal (25°C) temperature adversely affects plant growth, flowering, gamete development, embryo development, seed germination, inhibits the ability of pollinated flowers to develop into seeded fruit, inhibits fruit ripening and reduces yield. Drought resulting from insufficient rainfall and/or altered precipitation patterns is another important climatic stress factor for tomato often accompanied by relatively high temperature, in which evapo-transpiration is affected and photosynthetic kinetics and crop productivity reduced. Application of genomics in tomato, to discover novel and high throughput genetic and molecular technologies as an indirect selection tool, provides the potential for increasing efficiency of breeding by reducing the genotype × environment interaction, facilitating efficient introgression of superior alleles from wild species into plants promoting gene pyramiding control of quantitative traits and enhancing development of stress tolerant higher yielding varieties. Advances in genetics and genomics, have improved the understanding of structural and functional aspects of plant genomes. The CBF/NHX1/DREB1 genes have been used successfully to engineer drought tolerance in tomato. These genes are transcription factors implicated in tomato response to drought and heat stress. There are few tomato varieties/species which can easily adapt to stress tolerance as environmental conditions change. Some tomato varieties and wild species are heat and drought tolerant. The focus of research is to use tools and techniques to deliver global integration and overcome effects of environmental stresses on tomato.
Bell pepper (Capsicum annuum L., cv. ‘Mercury’) response to full and deficit irrigation was studied during
the 2005 growing season at Tal Amara research station in the Central Bekaa valley of Lebanon. Treatments
were (C) well-watered treatment receiving 100 % of crop evapotranspiration (ETcrop), and three water-
stressed treatments receiving irrigation at 80 (WS1), 60 (WS2) and 40 % (WS3) of ETcrop. Pepper seasonal evapotranspiration varied from a low of 275 mm in the more stressed treatment (WS3) to a high of 478 mm in the well irrigated control, while in WS1 and WS2 seasonal ET accounted for totals of 427 and 360 mm, respectively. Relative to plants grown in WS1 treatment (31.9 t ha–1), marketable fruit yields of C, WS2, and WS3 were reduced by 11.3, 12.2, and 38.2 %, respectively. WS1 and WS2 treatments enhanced fruit quality (dry matter and total soluble solids contents) compared with C. Water use efficiency at dry yield basis (WUEy) of the control was 0.35 kg m–3 while WS1, WS2 and WS3 treatments had WUEy higher by 22, 35 and 39 %, respectively. Radiation use efficiency (RUE) observed in the C and WS1 treatments (avg. 2.20 g MJ–1) was higher by 13 % in comparison to WS2 and WS3 treatments (avg. 1.96 g MJ–1), with no significant differences between C–WS1 and WS2–WS3. We concluded that WS1 treatment is recommended for drip irrigated bell pepper under field conditions in order to obtain higher yield and optimized WUE under the Mediterranean dry climate of the Central Bekaa Valley.
Key words. Capsicum annuum L. – deficit irrigation – evapotranspiration – radiation use efficiency – water use efficiency.
Consumer interest in the quality of vegetable products has increased in recent years especially for the beneficial effects of vegetables on human health. Vegetable quality is a broad term and includes physical properties, flavor, and health related compounds. The purpose of this paper is to review the recent literature of the main pre-harvest factors that can improve the quality of vegetables and consequently their beneficial role in human diet: The importance of genotype and grafted plants selection, the optimization of the environmental conditions (light and temperature) and the advantages and disadvantages of greenhouse in comparison to open field cultivation concerning product quality will be outlined first; followed by the optimization of agricultural practices in particular, water quantity and quality, mineral nutrition, salinity and growing system (e.g. soilless). The review will conclude by identifying several prospects for future research such as modeling of the nutritional value of vegetable crops.
Irrigation management strategy invites the quantification of crop response to irrigation frequencies. Conventionally, mulches increase the yield and water use efficiency (WUE) to a great extent by augmenting the water status in the root zone profile. A field study was carried out during the winter season (November-March) of 2003-2004 and 2004-2005 at the Central Research Farm of Bidhan Chandra Krishi Viswavidyalaya (Latitude 22°58'N, Longitude 88°31'E and altitude 9.75 m amsl), Gayeshpur, India, to evaluate the effect of irrigation frequencies and mulches on evapotranspiration rate from tomato crop field as well as leaf area index (LAI), fruit yield and WUE of the crop. The experiment was laid out in a split-plot design where three irrigation treatments {rainfed (RF); CPE50 and CPE25 where irrigation was given at 50 and 25 mm of cumulative pan evaporation (CPE)} were kept in the main plots and the subplots contained four mulch managements {no mulch (NM), rice straw mulch (RSM), white polyethylene mulch (WPM) and black polyethylene mulch (BPM)}. Under CPE25, tomato crop recorded significantly higher leaf area index (LAI) over CPE50 and rainfed condition. LAI value under BPM was 9-30% more over other mulches. Maximum variation of LAI among different treatments was recorded at 60 days after transplanting (DAT). Fruit yield under CPE25 was 39.4 Mg ha-1; a reduction of 7 and 30% has been obtained under CPE50 and RF condition. The use of mulch increased 23-57% yield in comparison to NM condition. Actual evapotranspiration rate (ETR) was 1.82 mm day-1 under CPE25 and declined by 15 and 31% under CPE50 and RF condition, respectively. The variation of ETR among different mulches became more prominent under maximum water stressed (RF) condition, whereas the variation was negligible under CPE25 frequency. Irrespective of mulching WUE was highest under moderately wet (CPE50) soil environment. Among different mulches, BPM was responsible for attaining the highest WUE value (25.1 kg m-3), which declined by 22, 21 and 39% under WPM, RSM and NM, respectively.
Drip irrigation has the potential to save water and mitigate foliar diseases for processing tomato production in Central Brazil.
Four experiments were carried out at Embrapa Vegetables, Brasília, Brazil, to establish irrigation management strategies during
vegetative, fruit development, and maturation growth stages of drip-irrigated processing tomato. Soil water tension (SWT)
threshold values ranging from 5 to 120kPa were evaluated. Plants growing under higher water deficit during the vegetative
stage showed root systems up to 10cm deeper than those irrigated more frequently. Maximum fruit yield was reached when irrigations
were performed at SWT thresholds of 35, 12, and 15kPa during vegetative, fruit development, and maturation growth stages,
respectively. Total soluble solids content was not affected by irrigation treatments during vegetative and fruit development
stages, but increased as SWT increased during fruit maturation growth stage.
In search of new innovations for saving irrigation water, fruit yield response and N-fertiliser recovery of greenhouse grown spring-planted tomato (Lycopersicon esculentum Mill., cv. F1 Fantastic) were assessed as influenced by deficit irrigation, imposed using either conventional deficit irrigation (DI) or partial root drying (PRD). Three irrigation treatments were tested: (1) FULL, control treatment where the full amount of irrigation water, which was measured using Class-A pan evaporation data, was applied uniformly on the two halves of plant-root zone; (2) PRD, 50% deficit irrigation in which wetted and partially dry halves of the root-zone were interchanged every irrigation; (3) DI, conventional deficit irrigation maintained at 50% deficit, compared to FULL irrigation, with water applied on the both halves of the root-zone. During a growth period of 153 days, the highest fruit yield of 145.4 t ha−1 was measured under FULL irrigation treatment, which was followed by PRD and DI treatments with statistically lower (P ≤ 0.01) yields of 114.6 and 103.4 t ha−1, respectively. Irrigation water use efficiencies (IWUE) of both deficit treatments were significantly (P ≤ 0.01) higher (52.7% for PRD and 38.3% for DI) compared to FULL irrigation. Nitrogen-fertiliser recovery was over 70%, with no significant difference among the irrigation treatments. Both deficit treatments (DI and PRD) showed lower values of leaf water potential, photosynthetic rate and stomatal conductance compared to FULL irrigation. Before irrigation, xylem-sap abscisic acid (ABA) concentrations were 28% and 38% higher under water-stressed deficit treatments DI0 and PRD, respectively, compared to FULL irrigation, and the high ABA concentrations was maintained only under PRD effect, following irrigation. The results of this work suggest that PRD practices can be viable and advantageous compared to conventional techniques to minimise crop-yield reductions during deficit irrigation.
Grapevine is a traditionally non-irrigated crop that occupies quite an extensive agricultural area in dry lands and semi-arid regions. Recently, irrigation was introduced to increase the low land yield, but a good compromise between grape quality and yield is of major importance for the achievement of high-quality products as wine. Therefore, water-use-efficient irrigation and regulated deficit irrigation programs need to be developed to improve water-use efficiency, crop productivity and quality in semi-arid crops.In the present review, current knowledge on grapevine responses to water stress is summarised. Based on this knowledge, the usefulness of different physiological parameters is discussed, and current knowledge on their applicability for water stress detection and irrigation management in grapevines is reviewed. Partial root drying (PRD) and regulated deficit irrigation (RDI) programs are proposed as the most promising tools for such purpose. Among RDI programs, several parameters are proposed as putative indicators of irrigation convenience and dosage. These are sap flow (measured by sap flow meters), trunk growth variations (measured by linear transducers of displacement, LTDs), canopy temperature (assessed by infrared thermometry), reflectance indices (measured by spectroradiometers or specifically designed instruments) and chlorophyll fluorescence (measured by either active or passive fluorometers). Advantages and disadvantages of all these tools are discussed.
A field experiment was conducted for two years (2013–15) to evaluate the response of tomato (Lycopersicon esculentum Mill.) to deficit irrigation (DI) with drippers. The options tried were either the regulated DI on the basis of climatological approach i.e. irrigation water equalling 0.6, 0.8 and 1.0 times the evapotranspiration (ET) or DI (0.6xET) at phenological stages (vegetative, flowering, fruiting, vegetative-cum-flowering, vegetative-cum-fruiting and flowering-cum-fruiting stages) and disrupting irrigation (15 days) at either of vegetative, flowering and fruiting stage. Compared with the full irrigation (FI; 78.0 Mg ha−1) the regulated deficit irrigation though did not affect the marketable fruit yield (MFY) at RDI0.8, there was loss of about one-fourth MFY with RDI0.6. Nevertheless the water productivity (19.2 kg m−3) was the maximum under RDI0.8. When the deficit irrigation was applied at different growth stages, MFY was rather improved by 4% with DI0.6(VS) while DI0.6(FL) showed little effect and a decline of 7% was monitored with DI0.6(FT). The DI applied at either of two stages (DI0.6(VS + FL); DI0.6(FL + FT); DI0.6(VS + FT)) resulted in 14–18% decline in MFY. The crop was able to tolerate interruptions of irrigation for 15 days at the above phenological stages i.e. simulating canal closures and the decline in yield was only 3–7%, the highest being at fruiting stages (IIFT). The major advantage of DI was improvement in quality in terms of total soluble solid, ascorbic acid, acidity and colour index (lycopene) though the fruit size was affected. It was concluded that benefits of deficit irrigation in terms of improved quality and water productivity while sustaining fruit yield could be achieved with regulated DI at 0.8xET and DI at 0.6xET during vegetative stage followed by flowering.
The influence of irrigation doses on standard and high lycopene tomato varieties has been analyzed during two years in one of the main processing tomato growing areas of Spain. Deficit irrigation (75% ETc) implied a mean reduction in water use of 28.2%, while it caused a significant reduction in the marketable production of 16.4% and increase in soluble solids (8.4%) and Hunter a/b ratio (2.4%). The effect on lycopene content was not significant. Increasing irrigation dose over the recommended 100% ETc had no significant effect on the agronomical performance, while it provoked a dilution effect reducing total soluble solids and lycopene content. The effects on 33 tomato volatiles were also analyzed, 11 of them related to main aroma notes and 22 to the background volatile profile. The effect of deficit irrigation on aroma was dependant on climatic conditions and it may either not have a significant effect on the aroma profile or may lead to higher logodor units in main aroma volatiles. High lycopene cultivars showed higher contents in most volatiles, including some volatiles originated in pathways that have not been related with carotenoid degradation processes. In both the fresh and processing tomato market the improvement of organoleptic and functional quality and the reduction of the impact of agriculture on environment represent main goals. The use of high lycopene cultivars and restricted irrigation would enhance the aroma of materials targeted to quality markets, contributing to increase the efficiency of water use in agriculture.
The nutritional composition of ten leafy vegetables (chicory, green lettuce, lamb’s lettuce, mizuna, red chard, red lettuce, rocket, spinach, Swiss chard, and tatsoi) and quality traits of the selected leafy vegetables in relation to the light intensity (low and high Photosynthetically Active Radiation; PAR) at time of harvest were determined. Irrespective of the light intensity at time of harvest, the highest leaf dry matter (DM), proteins, nitrate, P, K and Ca contents were observed in rocket followed by mizuna. The highest lipophilic antioxidant activity (LAA) was recorded in red lettuce and rocket, whereas ascorbic acid (AA) and total phenolic (TP) contents of red lettuce were higher compared to the other leafy vegetables. When leafy vegetables were harvested at low as opposed to high PAR, the leaf content was higher in DM, protein, K, Ca and Mg, hydrophilic antioxidant activity (HAA), and LAA by 12.5%, 10.0%, 12.6%, 23.7%, 14.1%, 11.9%, and 18.5%, respectively. The highest values in TP for chicory, green lettuce, lamb’s lettuce, mizuna, red chard, and red lettuce, were observed under high PAR.
European Community agricultural and environmental policies clearly aims at a rational use of natural resources, particularly water, and a reduction to zero in nitrogen pollution. These goals are impossible to reach without a day-by-day evaluation of the availability of water and nitrogen in the root zone. Therefore, a precise evaluation of root zone volume is essential to optimise crop water and nutrient management. A good estimation of the root zone volume requires an evaluation of the root elongation rate on three axes: depth, between rows and within rows. Horizontal root growth (between and within rows) may be assumed to be uniform and thus an uniform 3D root distribution can be calculated without taking into account differences in root density inside the root zone. Root elongation can be assessed on the basis of depth and width only. Tomato root growth rate was analysed using the data collected during the EU QUALITOM project. The project database is derived from observations made over three years in ten experimental stations located throughout the Mediterranean area and representing most of the tomato growing soil and climate conditions. Observed root growth was analysed and correlated with different soil characteristics, available water content, thermal day units accumulation, accumulated radiation and photosynthetic active radiation (PAR) in order to define some useful algorithms for modelling the soil volume occupied by roots.
The present paper reports research that focused on the effect of kaolin on the yield, quality and wateruse efficiency of the sweet pepper Capsicum annuum L., grown under different irrigation regimes. Theresearch was conducted in an open field with carbonate chernozem soil, at Stara Pazova (40 km northof Belgrade, Serbia). It lasted for three years (2011, 2012, and 2013). Three irrigation regimes and twokaolin treatments were compared. The irrigation regimes were: (i) full irrigation (F) ensuring 100% ofcrop evapotranspiration (ETc), (ii) deficit irrigation at 80% ETc (R1), and (iii) deficit irrigation at 70% ETc(R2). The kaolin treatments were: (i) control without kaolin (C) and (ii) treatment with kaolin application(K). The setup was a two-factorial, completely random block system, with three replications. The firstfactor was the irrigation regime and the second kaolin application.On average, the highest fresh sweet pepper yields were achieved under full irrigation (10 kg m−2). Also,FC and FK treatments resulted in the highest first-class, second-class and first + second class yields. Onaverage, the lowest percentage of sunburn was noted in the case of the FK treatment (10%), and thehighest with the R2C treatment (about 27%). The sugar content of the pepper was quite consistent, whilethe organic acid content varied from 15.0 mL g−1with R1C to 18.7 mL g−1with FK. The application ofkaolin and the irrigation regime did not have a statistically significant effect on the antioxidant activity ofthe pepper and ranged from 5538.4 to 6447.4 �mol TU g−1. The highest yield water use efficiency (yWUE)of first-class and first + second class yields was recorded with the FC, FK and R1C treatments. Throughoutthe study period, yWUE levels of the second-class yields, and of the total yield, were rather uniform,regardless of the type of treatment.
Tomato (Lycopersicon esculentum Mill.) root distribution was evaluated by the trench profile wall method at four trickle irrigation regimes (irrigation at soil water potential -10, -20,-40, and -60 kPa) in a 2-year field trial. Total root length intensity (m.m-2), final yield (t · ha-1) and fruit size (g/fruit) decreased with decrease in amount of water applied. In both years, tomato water use efficiency (kg · ha-1 · mm-1) was significantly lower with irrigation at -10 kPa than with any other irrigation regime studied. The largest proportion of tomato roots, 88% for 1989 and 96% for 1990, was found in the top 40 cm of the soil and rapidly decreased with depth. The high concentration of roots in the 30 to 40 cm layer was attributed to an horizon with high soil bulk density values, immediately below 40 cm, impeding deeper root penetration. Mast roots occurred in the emitter area, close to the plant. In rows 1.5 m apart, between 12% and 21% of total root length was found more than 0.5 m from the stem, which may have resulted from the interpenetration of roots from plants of adjoining rows.
Considering the current water scarcity of Northwest China, aiming at sustainable agricultural development in this region, it is required to identify and apply the most appropriate practices for water-saving, and yield and water productivity improvement. Relative to the tomato crop, a two-year field experiment was conducted in an arid region of Northwest China using drip irrigation and transparent plastic mulch to study the impacts of various soil matric potential thresholds (−10, −20, −30, −40 and −50 kPa) on yields, fruit quality and water productivity. A soil water balance was performed to estimate the seasonal actual ET (ETa) for every treatment and to relate it with the volume of water applied and yields achieved. Crop coefficients were determined from the crop density and height; for the non-stressed treatment the values of 0.30, 1.10 and 1.05 were obtained for the initial, mid-season and late season stages, respectively. A linear relationship between seasonal ETa and applied water was obtained. Tomato yields and ETa decreased with decreasing applied water but fruit quality did not: it was best under mild to moderate water stress (−30 to −40 kPa). Water productivity based on marketable-quality yields was the greatest when applied irrigation was 90% of the amount of irrigation required for no stress. This condition corresponds to a soil matric potential threshold of −40 kPa. However, a smaller stress may be desired in terms of irrigation management and a threshold of −30 kPa is then recommended.
A series of experiments is presented investigating short term and long term changes of the nature of the response of rate of CO2 assimilation to intercellular p(CO2). The relationships between CO2 assimilation rate and biochemical components of leaf photosynthesis, such as ribulose-bisphosphate (RuP2) carboxylase-oxygenase activity and electron transport capacity are examined and related to current theory of CO2 assimilation in leaves of C3 species. It was found that the response of the rate of CO2 assimilation to irradiance, partial pressure of O2, p(O2), and temperature was different at low and high intercellular p(CO2), suggesting that CO2 assimilation rate is governed by different processes at low and high intercellular p(CO2). In longer term changes in CO2 assimilation rate, induced by different growth conditions, the initial slope of the response of CO2 assimilation rate to intercellular p(CO2) could be correlated to in vitro measurements of RuP2 carboxylase activity. Also, CO2 assimilation rate at high p(CO2) could be correlated to in vitro measurements of electron transport rate. These results are consistent with the hypothesis that CO2 assimilation rate is limited by the RuP2 saturated rate of the RuP2 carboxylase-oxygenase at low intercellular p(CO2) and by the rate allowed by RuP2 regeneration capacity at high intercellular p(CO2).
The land area surrounding the Mediterranean Sea has experienced 10 of the 12 driest winters since 1902 in just the last 20 years. A change in wintertime Mediterranean precipitation toward drier conditions has likely occurred over 1902–2010 whose magnitude cannot be reconciled with internal variability alone. Anthropogenic greenhouse gas and aerosol forcing are key attributable factors for this increased drying, though the external signal explains only half of the drying magnitude. Furthermore, sea surface temperature (SST) forcing during 1902–2010 likely played an important role in the observed Mediterranean drying, and the externally forced drying signal likely also occurs through an SST change signal.
The observed wintertime Mediterranean drying over the last century can be understood in a simple framework of the region’s sensitivity to a uniform global ocean warming and to modest changes in the ocean’s zonal and meridional SST gradients. Climate models subjected to a uniform +0.5°C warming of the world oceans induce eastern Mediterranean drying but fail to generate the observed widespread Mediterranean drying pattern. For a +0.5°C SST warming confined to tropical latitudes only, a dry signal spanning the entire Mediterranean region occurs. The simulated Mediterranean drying intensifies further when the Indian Ocean is warmed +0.5°C more than the remaining tropical oceans, an enhanced drying signal attributable to a distinctive atmospheric circulation response resembling the positive phase of the North Atlantic Oscillation. The extent to which these mechanisms and the region’s overall drying since 1902 reflect similar mechanisms operating in association with external radiative forcing are discussed.
The effect of water stress on the growth, yield, and various morphological characteristics related to yield and eco-physiological responses of tomato was studied in two drought-tolerant cultivars, 'TM 0126' (TM) and 'VF-134-1-2' (VF) and two drought-sensitive ones, 'Kyokko' (KK) and 'Ratan' (RT). Water stress decreased yield, flower number, fruit set percentage and dry matter production in all cultivars, but the reduction was greater in drought- sensitive cultivars than in tolerant ones. Photosynthetic rate (Pr), transpiration rate (Tr), leaf water potential (Ψ(w)), and water use efficiency (WUE) were reduced, and leaf temperature (Tl) and stomatal resistance (r(s)) were increased by water stress in all cultivars. The reduction of Pr, Tr, Ψ(w) and WUE, however, was less pronounced in tolerant cultivars than in sensitive ones, whereas the increase of Tl and r(s) was more conspicuous in tolerant cultivars than in sensitive ones. After re-watering, all these eco-physiological responses returned to near normal state, but the recovery was more rapid and complete in tolerant cultivars than in sensitive ones. The better performances of tolerant cultivars under water stress and recovery after re-watering are attributed to the ability of plants to maintain a better water status and minimize the reduction of photosynthesis.
Abstract Water is an increasingly scarce resource worldwide and irrigated agriculture remains one of the largest and most inefficient users of this resource. Low water use efficiency (WUE) together with an increased competition for water resources with other sectors (e.g. tourism or industry) are forcing growers to adopt new irrigation and cultivation practices that use water more judiciously. In areas with dry and hot climates, drip irrigation and protected cultivation have improved WUE mainly by reducing runoff and evapotranspiration losses. However, complementary approaches are still needed to increase WUE in irrigated agriculture. Deficit irrigation strategies like regulated deficit irrigation or partial root drying have emerged as potential ways to increase water savings in agriculture by allowing crops to withstand mild water stress with no or only marginal decreases of yield and quality. Grapevine and several fruit tree crops seem to be well adapted to deficit irrigation, but other crops like vegetables tend not to cope so well due to losses in yield and quality. This paper aims at providing an overview of the physiological basis of deficit irrigation strategies and their potential for horticulture by describing the major consequences of their use to vegetative growth, yield and quality of different crops (fruits, vegetables and ornamentals).
BACKGROUND
The heightened consumer awareness for food safety is reflected in the demand for products with well-defined individual characteristics due to specific production methods, composition and origin. In this context, of pivotal importance is the re-evaluation of folk/traditional foods by properly characterizing them in terms of peculiarity and nutritional value. The subjects of this study are two typical Mediterranean edible products. The main morphological, biometrical and productive traits and polyphenol contents of three onion genotypes (Cipolla di Giarratana', Iblea' and Tonda Musona') and three long-storage tomato landraces (Montallegro', Filicudi' and Principe Borghese') were investigated. RESULTSSicilian onion landraces were characterized by large bulbs, with Cipolla di Giarratana' showing the highest bulb weight (605 g), yield (151 t ha(-1)) and total polyphenol content (123.5 mg kg(-1)). Landraces of long-storage tomato were characterized by low productivity (up to 20 t ha(-1)), but more than 70% of the total production was obtained with the first harvest, allowing harvest costs to be reduced. High contents of polyphenols were found, probably related to the typical small fruit size and thick skin characterizing these landraces. CONCLUSION
The present study overviews some of the most important traits that could support traditional landrace characterization and their nutritional value assessment. (c) 2013 Society of Chemical Industry
Scientia Horticulturae j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s c i h o r t i Effects of deficit irrigation on biomass, yield, water productivity and fruit quality of processing tomato under semi-arid Mediterranean climate conditions a b s t r a c t Processing tomato is a high water demanding crop, thus requiring irrigation throughout growing season in arid and semiarid areas. The application of deficit irrigation (DI) strategies to this crop may greatly con-tribute to save irrigation water. A two-year study was carried out in order to assess the effects of DI upon water productivity, final biomass, fruit yield and some quality traits of open-field processing tomato cv. Brigade in a typical semi-arid Mediterranean environment of South Italy. Four irrigation treatments were studied: no irrigation following plant establishment (V0); 100% (V100) or 50% (V50) evapotranspiration (ETc) restoration up to fruit maturity, 100% ETc restoration up to flowering, then 50% ETc restoration (V100-50). Total dry biomass accumulation was significantly depressed by early soil water deficit in V0; irrigation at a reduced rate (50% ETc) from initial stages (V50) or from flowering onwards (V100-50) did not induce any losses in final dry biomass. The marketable yield did not significantly differ among plots irrigated, but an averaged irrigation water saving of 30.4% in V100-50 and 46.2% in V50 was allowed as compared to V100. Marketable yield was negatively affected by the early water shortage in V0, due to the high fruit losses (>44%). The effects of DI on fruit quality were generally the converse of those on fruit yield. DI improved total soluble solids content, titratable acidity and vitamin C content. Water use efficiency was positively affected by DI, suggesting that the crop does not benefits from the water when this last is supplied to fulfil total crop requirements for the whole season. Yield response factor, which indicates the level of tolerance of a crop to water stress, was 0.49 for total dry biomass (Kss) and 0.76 for marketable yield (Ky), indicating that in both cases the reduction in crop productivity is proportionally less than the relative ET deficit. In conclusion, the adoption of DI strategies where a 50% reduction of ETc restored is applied for the whole growing season or part of it could be suggested in processing tomato, to save water improving its use efficiency, minimizing fruit losses and maintaining high fruit quality levels. This aspect is quite important in semi-arid environments, where water scarcity is an increasing concern and water costs are continuously rising.
In a previous study, important acclimation to water stress was observed in the Ramellet tomato cultivar (TR) from the Balearic Islands, related to an increase in the water use efficiency through modifications in both stomatal (g(s) ) and mesophyll conductances (g(m) ). In the present work, the comparison of physiological and morphological traits between TR accessions grown with and without water stress confirmed that variability in the photosynthetic capacity was mostly explained by differences in the diffusion of CO(2) through stomata and leaf mesophyll. Maximization of g(m) under both treatments was mainly achieved through adjustments in the mesophyll thickness and porosity and the surface area of chloroplasts exposed to intercellular airspace (S(c) ). In addition, the lower g(m) /S(c) ratio for a given porosity in drought acclimated plants suggests that the decrease in g(m) was due to an increased cell wall thickness. Stomatal conductance was also affected by drought-associated changes in the morphological properties of stomata, in an accession and treatment dependent manner. The results confirm the presence of advantageous physiological traits in the response to drought stress in Mediterranean accessions of tomato, and relate them to particular changes in the leaf anatomical properties, suggesting specific adaptive processes operating at the leaf anatomical level. © 2012 Blackwell Publishing Ltd.
Polyethylene glycol (PEG 6000)-induced water deficit causes physiological as well as biochemical changes in plants. The present study reports on the results of such changes in hydroponically grown tomato plants (Ly coper sicon esculentum Mill. cv. Nikita). Plants were subjected to moderate and severe levels of water stress (i.e. water potentials in the nutrient solution of-0.51 and-1.22 MPa, respectively). Water stress markedly affected the parameters of gas exchange. Net photosynthetic rate (Pn) decreased with the induction of water stress. Accordingly, a decrease in the transpiration rate (E) was observed. The ratio of both (Pn/E) resulted in a decrease in water use efficiency. One of the possible reasons for the reduction in Pn is structural damage to the thylakoids, which affects the photosynthetic transport of electrons. This was indicated by an increase in non-photochemical quenching and a reduction in the quantum yield of photosystem II. Furthermore, a decrease in both leaf water potential and leaf osmotic potential was observed, which resulted in a significant osmotic adjustment during stress conditions. Analysis of the physiological responses was complemented with a study on changes in proline content. In stressed plants, a 10-fold increase in proline content was detected compared with control plants. It is clear that water stress tolerance is the result of a cumulative action of various physiological and biochemical processes, all of which were affected by PEG 6000-induced water stress.
(Managing editor: Ping HE)
BACKGROUND: There is growing interest among consumers in baby leaf vegetables, mostly requested for mixed salads, both as fresh market products and ready-to-use vegetables. Fertilisation is one of the most practical and effective ways of controlling and improving the yield and nutritional quality of crops for human consumption. The optimal fertiliser concentration for baby leaf vegetables depends on the environmental conditions. The aim of the present work was to determine the effects of nutrient solution concentration (2, 18, 34, 50 or 66 mequiv L−1) during two consecutive growing seasons (spring and summer) on the yield and leaf quality of Lactuca sativa L. var. acephala grown in a floating system.
RESULTS: Marketable fresh yield, total dry biomass, leaf area index, macroelement (N, P, K and Mg) concentrations and nitrate and total chlorophyll contents increased in response to an increase in nutrient solution concentration, while the opposite trend was observed for root/shoot ratio and glucose, fructose, starch, total carbohydrate and protein contents. Plants grown in the spring season exhibited lower yield and growth (total dry biomass and leaf area index) but higher leaf quality (higher carbohydrate content and lower nitrate content) than those grown in the summer season.
CONCLUSION: The use of nutrient solution concentrations of 37 and 44 mequiv L−1 for the spring and summer seasons respectively could be adopted in the present conditions to improve marketable fresh yield and leaf mineral content, but with a slight reduction in some nutritional parameters. Copyright
Abstract Previously published data from tomato plants grown in nutrient solutions having one of three electrical conductivities (2, 12 and 17 mS cm−1) were analysed. The rate of water import into the fruit, and the proportion of this conducted by the xylem stream were calculated from the daily rates of transpiration and the net accumulation of water and calcium. The rate of water import decreased as the conductivity of the nutrient solution rose, the maximum daily import rates in the third week after pollination being 3.2, 3.0 and 1.8 g fruit−1 d−1 for fruit grown at 2, 12 and 17 mS cm−1, respectively. During fruit development, the proportion of water imported via the xylem fell from 8–15% to 1–2% at maturity. The principal source of water for tomato fruit growth was phloem sap. Based on the daily rates of net dry matter accumulation, respiration and phloem water import, the calculated dry matter concentration of the phloem sap declined from 7 to 3%, or from 12.5 to 7.8% during fruit development in low or high salinity, respectively. The similar dry matter accumulation of fruit grown at different salinities was due to changes in both volume and concentration of phloem sap. Potassium salts in tomato fruit were calculated lo have contributed –0.29, –0.48 and –0.58 MPa to total fruit osmotic potential in the 2, 12 and 17 mS cm−1 treatments, respectively, which accounted for 38% or 49% of the measured total osmotic potential of the 2 mS cm−1 or 17 mS cm−1 treatments. The contribution of hexoses to total fruit osmotic potential in the young fruit was from about –0.1 to –0.2 MPa at all salinities. The osmotic potential of tomato fruit is regulated more by potassium salts than by hexoses.
BACKGROUND: Tomato, one of the most important vegetables worldwide, contains a range of flavonoids and phenolic acids in addition to lycopene, which are regarded as potentially useful compounds with respect to health benefits. Composition data in fresh tomatoes vary due to genetic and environmental factors and cultural practices. Breeding programs aim to produce tomatoes with enhanced levels of flavonoids and other phenolics.RESULTS: The present paper gives an overview of flavonoids, stilbenoids and other phenolics reported to occur in tomato fruits. Contents are reported for a wide range of cultivars and types. Metabolism of phenolics during fruit maturation and tissue location are described, and an overview of measured contents is given. Effects of environmental conditions and cultural practices are estimated using available literature. Recent literature on transgenic tomatoes is included, and possibilities for regulating phenolic contents in tomatoes are discussed.CONCLUSION: The literature review clearly discloses a rapidly growing interest in flavonoids and other phenolics in tomato fruits and products made thereof. This is particularly connected to the antioxidant properties of these compounds as well as other possible health effects. Choice of cultivar and effects of environment and agronomic practices are important factors with respect to phenolic qualities and quantities of tomatoes. Copyright © 2009 Society of Chemical Industry
The responses of two sugar beet genotypes, 24367 (putative droughttolerant) and N6 (putative drought intolerant), to drought and nutrientdeficiency stress were investigated in an attempt to identify reliable andsensitive indicators of stress tolerance. In glasshouse-grown plants of bothgenotypes, relative water content (RWC) of the leaves decreased and leaftemperature increased in response to drought stress. Genotype differences inresponse to drought included leaf RWC, glycine betaine accumulation, alterationof shoot/root ratio and production of fibrous roots. Thus, in comparison to N6,genotype 24367 lost less water from leaves, produced more fibrous roots,produced more glycine betaine in shoots and tap roots and had a much reducedshoot/root ratio in response to withholding water for up to 215 h.The hydraulic conductance and sap flow of sugar beet seedlings grown innutrientculture decreased when subjected to nitrogen deficiency stress. Under nitrogensufficient conditions sap flow was greater in 24367 than in N6. The resultsindicate that genotype 24367 is more tolerant to stresses induced by water andnitrogen deficiency and that increased fibrous root development may be a majorfactor in increasing sap flow via a concomitant enhancement of aquaporinactivity.
Measurements of the quantum yields of chlorophyll fluorescence and CO2 assimilation for a number of plant species exposed to changing light intensity and atmospheric CO2 concentrations and during induction of photosynthesis are used to examine the relationship between fluorescence quenching parameters and the quantum yield of non-cyclic electron transport. Over a wide range of physiological conditions the quantum yield of non-cyclic electron transport was found to be directly proportional to the product of the photochemical fluorescence quenching (qQ) and the efficiency of excitation capture by open Photosystem II (PS II) reaction centres (Fv/Fm). A simple fluorescence parameter, ΔφF/φFm, which is defined by the difference in fluorescence yield at maximal φFm, and steady-state φFs, divided by φFm, can be used routinely to estimate changes in the quantum yield of non-cyclic electron transport. It is demonstrated that both the concentration of open PS II reaction centres and the efficiency of excitation capture by these centres will determine the quantum yield of non-cyclic electron transport in vivo and that deactivation of excitation within PS II complexes by non-photochemical processes must influence the quantum yield of non-cyclic electron transport.
An analysis of deficit irrigation in three quite different situations was conducted to better understand the potential benefits and risks associated with this irrigation strategy. Existing crop yield functions and cost functions, developed independently of the present research, were used to estimate the levels of applied water that would produce maximum net income in each situation. These same functions were also used to estimate the degree to which the three crops could be under-irrigated without reducing income below that which would be earned under full irrigation. The analysis encompassed wheat production in the northwestern USA, cotton production in California and maize production in Zimbabwe. Results suggest that (1) deficits of between 15% and 59% would be economically optimal, depending on the circumstances, and (2) the estimated margin for error in these estimates is quite wide.
"Long-storage" tomato ( Solanum lycopersicum L.) is a niche product typical of the Mediterranean area, traditionally cultivated under no water supply, the fruits of which combine a good taste with excellent nutritional properties. High-performance liquid chromatography coupled with diode array detection and electron spray-mass spectrometry (HPLC/DAD/ESI-MS) was used to identify the phenolic profile in 10 landraces of long-storage tomato, grown under a typical semiarid climate, as compared to a processing tomato hybrid cultivated in the same environment, under both well-irrigated and unirrigated conditions. Sixteen different secondary metabolites, belonging to the classes of cinnamoylquinic acids and flavonoids, were identified. Quantitative analyses were also performed to monitor the changes in the phenolic content along the batch. The results highlighted that landraces originating from the same area exhibit different fruit morphologies but own a similar biochemical profile. Moreover, the two controls (well irrigated and unirrigated) are placed into the same cluster, suggesting that these secondary metabolites in tomato fruits may be more genetics-dependent than environment-dependent. Given the analysis of phenols nowadays represents a useful tool to assess the genetic variability in tomato, these compounds could be adopted as chemotaxonomic markers in the traceability of this niche product.
The physiological traits underlying the apparent drought resistance of 'Tomàtiga de Ramellet' (TR) cultivars, a population of Mediterranean tomato cultivars with delayed fruit deterioration (DFD) phenotype and typically grown under non-irrigation conditions, are evaluated. Eight different tomato accessions were selected and included six TR accessions, one Mediterranean non-TR accession (NTR(M)) and a processing cultivar (NTR(O)). Among the TR accessions two leaf morphology types, normal divided leaves and potato-leaf, were selected. Plants were field grown under well-watered (WW) and water-stressed (WS) treatments, with 30 and 10% of soil water capacity, respectively. Accessions were clustered according to the leaf type and TR phenotype under WW and WS, respectively. Correlation among parameters under the different water treatments suggested that potential improvements in the intrinsic water-use efficiency (A(N)/g(s)) are possible without negative impacts on yield. Under WS TR accessions displayed higher A(N)/g(s), which was not due to differences in Rubisco-related parameters, but correlated with the ratio between the leaf mesophyll and stomatal conductances (g(m)/g(s)). The results confirm the existence of differential traits in the response to drought stress in Mediterranean accessions of tomato, and demonstrate that increases in the g(m)/g(s) ratio would allow improvements in A(N)/g(s) in horticultural crops.
In order to assess the effect of soil water deficit (SWD) during fruit development and ripening, on yield and quality of processing tomato under deficit irrigation in the Mediterranean climate, an open-field experiment was carried out in two sites differing from soil and climatic characteristics, in Sicily, South Italy. Six irrigation treatments were studied: no irrigation following plant establishment (NI); 100% (F=full) or 50% (D=deficit) ETc restoration with long-season irrigation (L) or short-season irrigation up to 1st fruit set (S); and long-season irrigation with 100% ETc restoration up to beginning of flowering, then 50% ETc restoration (LFD). The greatest effect of increasing SWD was the rise in fruit firmness, total solids and soluble solids (SS). A negative trend in response to increasing SWD was observed for fruit yield and size. Tough yield and SS were negatively correlated, the final SS yield under the LD regime was close to that of LF, and 47% water was saved. However, SS seems to be more environmental sensitive than SWD, since it varied more between sites than within site. The variations between sites in fruit quality response to deficit irrigation demonstrate that not only SWD but also soil and climatic characteristics influence the quality traits of the crop.
Florida is the largest producer of fresh-market tomatoes in the United States. Production areas are typically intensively managed with high inputs of fertilizer and irrigation. The objectives of this 3-year field study were to evaluate the interaction between N-fertilizer rates and irrigation scheduling on yield, irrigation water use efficiency (iWUE) and root distribution of tomato cultivated in a plastic mulched/drip irrigated production systems. Experimental treatments included three irrigation scheduling regimes and three N-rates (176, 220 and 230 kg ha-1). Irrigation treatments included were: (1) SUR (surface drip irrigation) both irrigation and fertigation line placed right underneath the plastic mulch; (2) SDI (subsurface drip irrigation) where the irrigation line was placed 0.15 m below the fertigation line which was located on top of the bed; and (3) TIME (conventional control) with irrigation and fertigation lines placed as in SUR and irrigation being applied once a day. Except for the "TIME" treatment all irrigation treatments were controlled by soil moisture sensor (SMS)-based irrigation set at 10% volumetric water content which was allotted five irrigation windows daily and bypassed events if the soil water content exceeded the established threshold. Average marketable fruit yields were 28, 56 and 79 mg ha-1 for years 1-3, respectively. The SUR treatment required 15-51% less irrigation water when compared to TIME treatments, while the reductions in irrigation water use for SDI were 7-29%. Tomato yield was 11-80% higher for the SUR and SDI treatments than TIME where as N-rate did not affect yield. Root concentration was greatest in the vicinity of the irrigation and fertigation drip lines for all irrigation treatments. At the beginning of reproductive phase about 70-75% of the total root length density (RLD) was concentrated in the 0-15 cm soil layer while 15-20% of the roots were found in the 15-30 cm layer. Corresponding RLD distribution values during the reproductive phase were 68% and 22%, respectively. Root distribution in the soil profile thus appears to be mainly driven by development stage, soil moisture and nutrient availability. It is concluded that use of SDI and SMS-based systems consistently increased tomato yields while greatly improving irrigation water use efficiency and thereby reduced both irrigation water use and potential N leaching.
The quenching action of dibromothymoquinone on fluorescence and on primary photochemistry was examined in chloroplasts at minus 196 degrees C. Both the initial (F0) and final (FM) levels of fluorescence as well as the fluorescence of variable yield (FV equals FM minus FO) were quenched at minus 196 degrees C to a degree which depended on the concentration of dibromothymoquinone added prior to freezing. The initial rate of photoreduction of C-550 at minus 196 degrees C, which was assumed to be proportional to maximum yield for primary photochemistry, phipo, was also decreased in the presence of dibromothymoquinone. Simple theory predicts that the ratio FV/FM should equal phipo. Excellent agreement was found in a comparison of relative values of phipo with relative values of FV/FM at various degrees of quenching by dibromothymoquinone. These results are taken to indicate that FO and FV are the same type of fluorescence, both emanating from the bulk chlorophyll of Photosystem II. Dibromothymoquinone appears to create quenching centers in the bulk chlorophyll of Photosystem II which compete with the reaction centers for excitation energy. The rate constant for the quenching of excitation energy by dibromothymoquinone is directly proportional to the concentration of the quencher. Rate constants for the de-excitation of excited chlorophyll molecules by fluorescence, kF, by nonradiative decay processes, kD, by photochemistry, kP, and by the specific quenching of dibromothymoquinone, kQ, were calculated assuming the absolute yield of fluorescence at FO to be either 0.02 or 0.05.