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Arbuscular mycorrhizal fungi in the rhizosphere of banana and plantain and the growth of tissue culture cultivars
Abstract
The status of arbuscular mycorrhizal fungi (AMF) in banana and plantain (Musa spp.) farming systems was studied in central Kenya. Soils and roots were sampled from 50 farms. Mean colonization frequency and intensity of 56.9% and 36.8% signified presence of viable infective propagules. Total of 22 morphotypes were recovered and six identified to known species. Fungal communities comprised of Acaulosporaceae, Glomaceae, Archaeosporaceae and Gigasporaceae dominated by species in Glomus. Acaulospora produced 52.2% of the spores with Acaulospora scrobiculata the most abundant and dominant at the rhizosphere of 60% of the cultivars. Mean colonization, spore abundance, species richness and diversity at rhizosphere of cultivars were not significant (p < 0.05). Nonetheless, Monte Carlo significant test revealed significant (p = 0.04) interaction between cultivars and AMF variables. Principal component analysis indicated high correspondence of cultivars in similar ploidy and AMF variables and Co-inertia analysis indicating AAA-Cavendish cultivars to relate strongly to spore variables and AAA-Gros Michel with colonization. Pearson correlation coefficients indicated soil phosphorus and carbon to negatively affect colonization and carbon to positively affect spore abundance and species richness. Musa systems maintained high species richness and low spore abundance. Trap plants of unrelated species did not differ in their effects on AMF variables.
... También se encontró una relación positiva entre la colonización de HMA y el porcentaje de carbono orgánico en suelo (4.9 -7.7 %), mientras que el contenido de fósforo total en suelo (603 -1673 ppm) se relacionó negativamente con la colonización (Guerrero-Ariza y Posada, 2017). Asimismo, Jefwa et al. (2012) encontraron que el contenido de P (30.7 mg/kg) y el carbono orgánico en suelo (1.9 %) de plantaciones de banano se correlacionan negativamente con la colonización, no obstante, el carbono orgánico también tuvo un efecto positivo en la abundancia de esporas y en la riqueza de especies. A pesar de la importancia del cultivo de banano en el estado de Colima, no existen reportes sobre los factores edáficos que promueven o disminuyen la abundancia y colonización de HMA. ...
... Una explicación a esto es que la concen-tración alta de nutrientes presente en suelo arcilloso puede reducir el desarrollo de la micorriza arbuscular (Carrenho et al., 2007). Se ha reportado que un incremento de P en suelo se correlaciona negativamente con la colonización de HMA (Guerrero-Ariza et al., 2017) y con la abundancia de esporas (Jefwa et al., 2012). No obstante, los resultados obtenidos en el análisis de componentes principales indican que el P influye positivamente en la abundancia de esporas, pero no tiene un efecto sobre la colonización (Tabla 2). ...
... Las discrepancias en la influencia de este factor en la abundancia de esporas y colonización de HMA pueden deberse a que esta última es más sensible a las concentraciones de P comparado con la producción de esporas (Liu et al., 2016). Con respecto al pH, este factor tuvo una influencia positiva en la colonización de época de sequía (Tabla 3), lo cual coincide con lo reportado por Jefwa et al. (2012), quienes encontraron que el pH favorece la colonización, pero disminuye la abundancia de esporas. Aunado a esto, se sabe que el pH se correlaciona positivamente con la CIC, es decir, un incremento del pH aumenta la concentración de cationes intercambiables (Ca Mg, K) y, por lo tanto, mayores nutrientes disponibles para la planta (Gaidashova et al., 2010). ...
Background: Edaphic properties influence the abundance of spores and the colonization of arbuscular mycorrhizal fungi, however, there are few studies of the properties that have a greater impact on arbuscular mycorrhiza in the dry and rainy season in banana crops.
Objectives: To determine the influence of edaphic properties on the abundance of spores and the colonization of mycorrhizal fungi in banana plantations in two seasons of the year.
Methods: Soil and banana roots were collected in Tecoman, Colima, and the influence of edaphic properties on the abundance of spores and colonization of mycorrhizal fungi was determined by principal component analysis.
Results and conclusions: The highest value of spore abundance (1700 spores/100 g of soil) and colonization of mycorrhizal fungi (63.3 %) were found in the rainy and dry season, respectively. Twenty three morphotypes of the Claroideoglomus, Acaulospora, Rhizophagus, Racocetra, Funneliformis, and Glomus genera were identified, the latter being the most common. The edaphic properties that promote or reduce the abundance of spores and colonization of AMF differ in each season, with a greater number of factors that influence the abundance of spores.
... In order to develop and apply a specific AM as the main root associate in any crop, good knowledge of the ecology of natural AM flora in diverse cultivated fields of the crop is quite important. Exploration of AM fungal species associations in the native fields in relation to the soil environmental characteristics is vital to advance (Jefwa et al. 2012) in ecology of specific mycorrhiza. ...
... Natural AM fungal population in a farming system is the resultant of ecological and evolutionary interrelationship between plants, soil and other environmental factors in the field, where each mycorrhizal species has certain functions to play (Jefwa et al. 2012) and specific competence in relation to the existing field environment conditions. In this connection, broad ecological field survey of AM fungal associations are highly relevant to the context of sustainable soil fertility management not only banana, but all crops. ...
... Species such as F. mosseae and G. microcarpum showed no host specificity and were found with all the 13 widely cultivated banana varieties of South India. Certain degree of host specificity has been reported for certain species of Acaulospora and Glomus in different banana varieties (Jefwa et al. 2012). Although, different AMF species may vary in the capacity to produce different amount of spores in a fixed time period (Bever et al. 1996) the exact reasons of higher spore density of Glomus and Acaulospora than that of others in South Indian fields need to be investigated further, because spore production depends on multiple factors. ...
This is the first report of a comprehensive ecological investigation of AMF symbiosis in banana over a very broad zone of its commercial cultivation, South India. The AMF characteristics in relation to specific banana varieties, soils and seasons are carried out. This baseline data has global use for mycorrhizal applications in the crop. Spore density and percentage root colonization in relation to soil fertility parameters, seasons and soil series, along with other ecological parameters are assessed as per standard methods. Altogether 14 different AMF species of 13 different banana varieties, in terms of spore density and percentage colonization from 47 different soil series of South India are discovered. Among the 14 AMF species observed, Dentiscutata nigra is a new report in banana. Shannon’s diversity index and Simpson’s index over seasons are measured. Evenness in AM fungal population in banana fields in the monsoon was higher than that of summer. Presence of over 30% AMF root colonization in majority of banana varieties revealed its significance in the crop.
... This clearly showed that there was a diverse core of AMF taxa already preestablished in a large part in the banana field soils. The AMF communities within the banana field soils can be considered highly diverse as compared to the diversity found when morphological description used (Jefwa et al, 2012). In this study the Illumina Miseq technology allowed the identification of 25 species distributed in 12 genera within the three agroecological zones. ...
... However, previous studies revealed that banana and plantain fields were dominated by the genera Acau-lospora (Jaizme-Vega & Azcón, 1995;Fotso et al., 2016). The dominance of an AMF genus may not be linked to the presence of a particular crop species or variety in an agro-ecological zone (Jefwa et al., 2012). Indeed similar agroecological zones (Abengourou and Azaguié) exhibited the dominance of the genus Rhizophagus in cassava rhyzosphere fields (Séry et al, 2018) while PCA analyses of the banana field soils did not allow a clear cut deliniation of each agroecological zone. ...
The arbuscular mycorrhizal fungi (AMF) communities of plantain rhizosphere soils were investigated by Illumina MiSeq technology. We analyzed the possible correlation between soil characteristics, AMF abundance and community composition in plantain field soils within three different agro-ecological zones. We used principal component analysis to test the relative contribution of each agro-ecological zone in explaining AMF community composition variation in field soils. Pearson correlations were used to identify the soil properties that significantly explained AMF community compositions within the three zones. The results showed that despite the fact that the three zones exhibited contrasted soils, AMF communities within the three zones were dominated by Glomeraceae, with Rhyzophagus as the main genus (72.75% of AMF identified genera). Soil types determined the distribution of AMF communities in plantain field soils, and this effect was attributed to total phosphorus, organic matter, Ca2+, Mg2+ and Na+. Les communautés des champignons mycorhiziens à arbuscules (CMA) des sols de la rhizosphère du bananier plantain ont été étudiées par la technologie Illumina MiSeq. Nous avons analysé la corrélation possible entre les caractéristiques du sol, l'abondance et la composition des communautés CMA dans les sols de bananiers plantains dans trois zones agro-écologiques différentes. Nous avons utilisé une analyse en composantes principales pour tester la contribution relative de chaque zone agro-écologique à l'explication de la variation de des communautés de CMA. Les corrélations de Pearson ont été utilisées pour identifier les propriétés du sol qui expliqueraient de manière significative la composition des communau-tés de CMA dans les trois zones. Les résultats ont montré que, malgré le fait que les trois zones présentaient des sols con-trastés, les communauté des CMA dans les sols des champs de plantains étaient dominée par la famille des Glomeraceae, Rhyzophagus étant le genre principal (72,75% des genres identifiés). Le type de sol a déterminé la distribution des commu-nautés de CMA dans les sols de bananier plantain, et cet effet a été attribué au phosphore total, à la matière organique, au Ca2+, au Mg 2+ et au Na+. Abstract Résumé
... A bananeira é uma espécie semiperene que vem crescendo em importância sócia-econômica na região noroeste paranaense, além disso, é uma planta micotrófica, capaz de beneficiar-se da presença de FMAs e apresenta uma alta dependência micorrízica (DECLERCK; PLENCHETTE; STRULLU, 1995;2002;OLivEiRA;OLivEiRA, 2005;JEFwA et al., 2012). ...
... Recentemente, Lermen et al. (2012) avaliaram a densidade de esporos de FMAs em Umuarama-PR de um solo cultivado com aveia preta (Avena strigosa Schreb), uma poacea como a braquiária e encontraram valores superiores a 10 esporos g -1 de solo seco, correspondendo a mais de 2 vezes a densidade de esporos observada no presente estudo. Jefwa et al. (2012) Na área com braquiária, a densidade de esporos de FMAs foi de 3,67 esporos g -1 de solo, similar a média de 3,4 a 6,5 esporos g -1 de solo observada por Santos et al. (2008), em cinco diferentes períodos de amostragem no estado de São Paulo em 2002/2003. Estes autores também observaram alta colonização radicular média por FMAs em torno de 73 a 78%, corroborando com a alta dependência micorrizíca da braquiária. ...
... India holds the first position of being the largest producer of bananas and nendran (AAB) is the most popular banana variety of Kerala, well suited for both culinary and table purposes, albeit the existing supply of the fruits in the market falls short of meeting the escalating demand (Singh et al., 2016). The banana industry faces several significant challenges, including reduced productivity, lack of disease-free planting materials and declining soil fertility, consequently leading to poor growth, yield and quality of banana fruits (Jefwa et al., 2012). To bridge the supply and demand gap in the banana industry, there is a requirement for an adequate supply of good quality banana fruits in the market. ...
... India holds the first position of being the largest producer of bananas and nendran (AAB) is the most popular banana variety of Kerala, well suited for both culinary and table purposes, albeit the existing supply of the fruits in the market falls short of meeting the escalating demand (Singh et al., 2016). The banana industry faces several significant challenges, including reduced productivity, lack of disease-free planting materials and declining soil fertility, consequently leading to poor growth, yield and quality of banana fruits (Jefwa et al., 2012). To bridge the supply and demand gap in the banana industry, there is a requirement for an adequate supply of good quality banana fruits in the market. ...
Piriformospora indica is an axenically cultivable fungal root endophyte that contributes multifaceted benefits to plants. The role of P. indica in improving quality parameters of ripe and unripe stages of banana (Musa acuminata) var. Nendran was investigated. The physical, biochemical and organoleptic status were quantified during the green (unripe) and ripe stages. Both shelf life and beta carotene content were enhanced in the fruits of P. indica-colonized plants compared to control. All physical parameters like, bunch weight, fruits per hand, fruit length, fruit weight and fruit diameter were significantly enhanced in bunches obtained from P. indica-colonized banana plants. Biochemical parameters viz., total sugars, pH, total reducing sugars, beta carotene, protein and carbohydrate contents were also substantially increased in fruits obtained from the fungus colonized plants. In contrast, crude fibre and moisture content were reduced in ripe fruits obtained from the colonized plants compared to their respective control plants. Beta carotene was increased by 93.9 per cent; and pH, total reducing sugars and acidity were increased progressively during ripening of the fruits obtained from the colonized plants. These fruits recorded 34 per cent more total sugars, which indicate the degree of sweetness of the fruit. The carbohydrate, fibre and moisture content were high in unripe banana fruits obtained from the colonized plants compared to control plants. The unripe fruits had 13.2 and 52.15 per cent high carbohydrate and protein contents respectively compared to the respective unripe control fruit. The present study also revealed that P. indica could enhance the shelf life of banana fruits by slowing down the ripening process, thereby increasing its marketability. Furthermore, sensory evaluation confirmed the overall acceptability of banana fruits from the endophyte colonized plants compared to fruits from the control plants. Thus P. indica-colonized banana plants render fruit quality improvement with enhanced shelf-life of fruits to a reasonable extent.
... Controlled inoculation in the germinators and then in the nursery favoured an important colonization of the roots of the plantain seedlings, first in the nursery and then after 14 weeks in the plantation. This confirms that plantain plants are highly mycotrophic [22,23]. The roots of inoculated plants contain abundant and essentially the structures of the strain constituting the inoculum (Rhizophagus intraradices isolated from the rhizosphere of plantain). ...
The difficulties of nurserymen and producers of plantains in Côte d’Ivoire are the high mortality rate of seedlings and the delays of growth in the field. The aim of this study is to improve quality and agronomic performance of plantain seedlings produced by PIF technique (plantain seedlings production based on macropropagation). The plantain shoot bulbs were inoculated before being placed in the germinator and seedlings from germinator were inoculated again during the weaning phase at nursery with AMFs (Rhizophagus intraradices). Root mycorrhizal colonization, growth parameters such as girth, height, total leaf area, biomass and entry into production were measured in nursery and on the field. The results showed that the root colonization rate of the plants inoculated with R. intraradices inoculum was higher (30.59%) than that of the native arbuscular mycorrhizal fungi (2.78%). All inoculated plants survived while non-inoculated plants had 27.69% of mortality rate. Inoculated plants had higher growth than non-inoculated plants. The organs of inoculated plants also had higher biomass than non-inoculated plants. Eleven months after planting, nearly 50% of the inoculated plants had started production, while only 5.67% of the non-inoculated plants had started production. Mycorrhization improved the vigor and vegetative growth of plantain seedlings. It could therefore be used as a solution for a sustainable plantain culture.
... Gambar 6 Struktur kolonisasi FMA pada tanaman serai wangi di lahan ternaungi (A-D). Arbuskula (a), hifa internal (hi), dan vesikula (v) (Bar = 20 µm).yang mempunyai tingkat ketergantungan yang rendah pada mikoriza(Jefwa et al. 2012;Karthikeyan et al. 2005), sedangkan tanaman bambu dan kopi dilaporkan oleh Das dan Highland (2010) merupakan tanaman yang mempunyai tingkat ketergantungan moderat sampai tinggi pada mikoriza. Tanaman aren merupakan anggota Famili Arecaceae yang anggotanya di antaranya ialah tanaman kurma (Phoenix dactylifera). ...
Arbuscular mycorrhiza (AM) characteristics of citronella grass in the field have not been reported. This research aimed to study the AM characteristics of citronella grass grown in unshaded and shaded fields. The roots of citronella grass were collected from citronella grass plantations in Cianjur, West Java. The root samples were analyzed for AM structures, namely entry points, intercellular hyphae, arbuscules, and vesicles. The results showed that the citronella grass form AM colonization. The quality of root colonization differed between the two cultivation systems. The unshaded citronella grass had higher root colonization compared to shaded citronella grass. In the unshaded citronella grass, the number of arbuscules was 7 per cm of root length, whereas in the shaded citronella grass was 4 per cm of root length. The types of arbuscules observed were arum and intermediate. There were no differences in the number of entry points in the two cultivated systems, which was 3,5 entry points per cm of root length. The numbers of vesicles and internal hyphae in unshaded citronella grass were lower than that of in the shaded citronella grass. In the unshaded citronella grass, the number of vesicles and intracellular hyphae were 1,5 and 8,5 per cm root length, whereas in the shaded citronella grass were 3,5 and 11 per cm root length, respectively. Shading plants grown in the field were bamboo, banana, coffee, tea, and sugar palm. All the shading plants formed AM symbiosis with a colonization value of 7 to 30%. This research indicates that arbuscular mycorrhiza is an important component in the citronella grass cultivation in unshaded and shaded fields.
Keywords: Arbuscule, entry point, intercellular hyphae, root colonization, vesicle
... Citrus, for example, are strongly mycorrhizal dependent (Ortas, 2012). Bananas with AMF benefit from enhanced plant nutrition and reduced Janke, Blackburn, Khan, Al Busaid, Al Busaidi, Al Hinai, Mushtaque nematode lesions (Jaizme-Vega and Pinochet, 1997), some protection from Fusarium wilt disease (Castillo et al., 2019), but there can be significant differences between colonization and benefits from the AMF that are different among different banana cultivars (Jefwa et al., 2012). ...
Organic soil amendments have been used in Oman since prehistoric agriculture began and are still being used today. Recently, interest in certified organic farming, and the use of organic soil amendments to enhance soil quality has motivated more research on traditional and new diverse soil amendment products. In addition, the arid climate of Oman combined with sandy soils benefit from non-traditional soil amendments and nutrient sources, such as treated human waste and wastewater. These two are not allowed in certified organic farming but offer sustainable solutions to building soil health for non-certified crops. This review will cover studies of soil quality in Oman related to the comparison of these various amendments, including manures, composts, organic mulch materials, biochar, ash, and others. In general, most of these amendments improve the soil by adding organic carbon, increasing the water holding capacity, improving infiltration rate, and stimulating or providing habitat and food sources for diverse soil microbiological communities. Some amendments can also help crops overcome some of the stresses of agriculture in Oman, such as soil salinity, heat and drought. Most also provide macro and micronutrients for crop growth. Some anti-quality factors may be present however, such as a high carbon to nitrogen ratio in some mulches, or high heavy metal content, human pathogens, and pharmaceutical residues in treated waste or wastewater. Biochar may have a positive or negative effect on soil microbes, depending on the source material and temperature of combustion can result in byproducts that inhibit microbes. The value of soil microorganisms has been shown in organic cropping systems, and several new species have been discovered in Oman. Some of these provide possibilities for biocontrol of pathogens, and increased salt tolerance in crops like tomato. Though much valuable research has been done in Oman and the rest of the world, there is much left to be done to determine the effects of these organic amendments over the long term, and also the interactions among various amendments, soil conditions, soil microbes, and on crops grown with different irrigation methods and cropping systems.
... (2010) who reported the same genera was the most dominant in their study. However similar observation of Glomus being dominant followed by Acualospora was reported in different crops such as banana (Jefwa et al., 2012), tomato (Songachon et al., 2012 and apple (Summuna et al., 2019). The point that an equal number of spores of genus Glomus were present in both the CSA and non-CSA agricultural practices, was in agreement with the work by Dandan and Zhiwei, (2007) who reported that Glomus is highly dominated by small spores and widely distributed in a wide range of ecological conditions. ...
Fruit and vegetable value chain actors in developing countries experience postharvest losses of 20 – 50% depending on the crop and management practices. One of the reasons for such loss is mentioned to be lack of affordable technologies to enhance produce storability during handling after harvest. Temperature management serves as number one practice for extending shelf life of fresh produce. CoolBot is a device coupled to room air conditioner capable of dropping the room temperature to as low as 2oC. Storage rooms installed with the technology seem suitable for handling of fresh fruits and vegetables over extended period. However, most value chain actors aware of the technology are skeptical of its performance and cost effectiveness during utilization. This study was designed to evaluate performance and cost effectiveness of two CoolBot Cold-rooms (CB-CR) independently set at temperature of 13±1oC and 16±1oC, respectively. Tomato fruits of the variety Assila harvested at three maturity stages were used during the evaluation. A 2x3 factorial experiment arranged in a Completely Randomized Design (CRD) with two factors; storage condition (CB-CR at 13±1oC and CBCR at 16±1oC) and Maturity stage (mature-green, breaker and light-red) was used. Following 42 days storage of 6 crates (14.25kg each) per treatment combination, results indicated no significant interaction of maturity stage and storage condition among variables. However, external fruit colour change (L*C*h*), marketable fruits (%), soluble solid content (%Brix), titratable acidity (MeqL-1), weight loss (%) and firmness-compression (kg/mm2) varied with maturity stages. External fruit colour change from yellow yellow-green (L*C*h* = 57, 31.7, 110) to yellow yellow-red (L*h*C*= 39.7, 42.3, 43.0) was delayed more on mature green (MG) compared to other stages at both CB-CR (13±1oC and 16±1oC). Percentage marketable fruits was much higher on mature green fruits (84.83%), followed by Breakers (60.91%) and light red (48.58%). Based on electricity consumption, storage of tomato at CB-CR 16±1oC (160.2 KWh) was more beneficial than at CB-CR 13oC (272.7 KWh) due to less power consumption. It is therefore imperative to conclude that, more benefit can be realized when CB-CR storage is combined with proper harvest maturity stage. More studies are required to map price change of tomato over seasons for proper storage timing using the technology along the year.
... Various species of AMF have been reported from different plants with Glomus, Acaulospora, Gigaspora being the most common one. Jefwa et al. (2012) isolated 22 AMFs from the rhizospheric zone of banana and plantain. These fungi belonged to Acaulospora sp., Archaeospora sp., Glomus sp., Scutellospora sp., and Gigaspora sp., and the highest abundance in the banana rhizosphere was of Acaulospora scrobiculata. ...
Extreme cold environments harbor novel psychrotrophic microbes bestowed with the characteristic to grow in diverse cold habitats worldwide ranging from permanently ice-covered lakes, glaciers, snow, ice cap cores of deep oceans, cloud droplets, and Antarctica. To study the survival mechanism under low temperature, diverse psychrotrophic microbes act as model organisms. These microbes have potentially important and multiple commercial utilities as enzymes, peptides, biodetergents, antibiotics, and bioactive compounds in different areas of industries, agriculture, and pharmaceutics along with multifunctional plant growth-promoting traits. In addition, it also provides an environment-friendly and economically captivating means for improving nutrition acquisition, plant hormone production, and release of siderophores to trigger crop growth under cold stress. Such psychrotrophic microbes are of immense potential for high-altitude and psychrotrophic agroecosystems due to their unique climatic adaptations. Hence, it is of utmost importance to isolate, characterize, and conserve these economically important microbes to reveal their functional characteristics under cold temperature. The present chapter provides insights into the biodiversity of psychrotrophic microbes, their adaptation strategies, and their potential applications in agriculture, medicine, industry, food, and allied sectors.
... Various species of AMF have been reported from different plants with Glomus, Acaulospora, Gigaspora being the most common one. Jefwa et al. (2012) isolated 22 AMFs from the rhizospheric zone of banana and plantain. These fungi belonged to Acaulospora sp., Archaeospora sp., Glomus sp., Scutellospora sp., and Gigaspora sp., and the highest abundance in the banana rhizosphere was of Acaulospora scrobiculata. ...
Plant–microbe interactions are crucial for many ecological processes. These interactions majorly take place in the rhizosphere and are mediated by the secretion of organic compounds by plant roots. These compounds act as signalling molecules and also as carbon sources for microbes. Microbial community in the rhizosphere is very diverse and consists of bacteria, archaebacteria, viruses, fungi, actinomycetes, protozoans, arthropods, algae, and nematodes. The rhizospheric microbes promote plant growth by different mechanisms such as biocontrol activity, phytohormone secretion, siderophore production, mineral solubilization, nitrogen fixation, and enzyme production. Since, a large proportion of microbial diversity is still not cultured, the detection and phylogenetic characterization of such un-/non-cultured microorganisms require advanced molecular techniques viz. metagenomics, metabolomics, metatranscriptomics, and metaproteomics. Several factors affect the rhizosphere microbial population, including root exudates, type and age of the plant, status of plant health, and application of fertilizers, pesticides, and amendments. Plant growth-promoting microbes of the rhizosphere can be used as biofertilizers and biocontrol agents and rhizosphere competence is an important factor that determines their success. This chapter discusses all these aspects of rhizospheric microbial communities, especially their occurrence, distribution, and functions.
... Increase in plant growth parameters was due to improved nutrient uptake brought about by the symbiotic association of plants withAMF (Jeffries et al., 2003). Among various species of Glomeromycota, Glomus species are most effective in promoting growth of banana plantlets during the acclimatization as well as post transplants into the fields as demonstrated by YanoMelo et al., 1999; Koffi and Declerek, 2015.Colonization of plant roots by AMF increases crop productivity through improved access to nutrientsand water and suppression of pest and diseases(Jefwa et al., 2010(Jefwa et al., , 2012 Conclusion:AMF inoculant application is an excellent growth promoter and best treatment in promoting the growth of micro propagated banana plantlets. As AMF showed remarkable increase in Plant growth parameters: plant height, leaf area, and dry weight of shoots and roots of banana plantlets inoculated with AMF, it can be used as a potential agent for sustainable agriculture in the Marathwada region.Future Prospectives:Many reports have demonstrated the effectiveness of AMF in drought and salinity(Augé, 2001), as well as a bio control agent against nematodes due to suppressive effects of the fungi on their reproduction(Elsen et al., 2003), this study is per sued further on this line, as major areas in Marathwada region is now facing water scarcity and nematode infestations in banana plantation.Despite its enormous potential, the application of AMF has not been fully adopted by farmers so far. ...
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which this book would not have come into existence.
... They increase root surface area and enhance ability to explore nutrients beyond the nutrient depletion zone (Smith and Read, 1997). Indeed, different AMF species have been observed to colonize plantain roots (Jefwa et al., 2012). Inoculated plants with AMF fungi can improve crop production under water deficit conditions. ...
A pot experiment was conducted to assess the potential of arbuscular mycorrhizal fungi to improve plantain resistance to water deficit conditions. For this purpose, three sources of inoculants were used: (1) a strain of Glomus clavisporum isolated from plantain rhizosphere in Azaguié region; (2) a fungal complex isolated from plantain rhizosphere in Azaguié (5° 38 'N, 4°05' W); (3) a fungal complex isolated from plantain rhizosphere in Bouaflé (6°59 'N, 5°45' W). These inoculants were tested, using the plantain varieties Fhia 21 and Orishele, using three levels of water supply (100, 60 and 30%). Plant growth and others physiological parameters were measured and compared for all the treatments, including the control. Comprehensively, root colonization decreased with the reduction of water supply. The mycorrhizal plants had widest leaves, highest leaf water and chlorophyll contents for any level of water supply. As same, arbuscular mycorrhizal fungi significantly increased soluble sugars and proline contents with water deficit. These results demonstrated that arbuscular mycorrhizal fungi increase plantain photosynthetic activity and thus impact plantain growth in any water supply condition. The proline and soluble sugars are were sensitive molecules to water stress conditions and their productions in the plantain are were improved in presence of mycorrhizal fungi. Une expérience en pot a été réalisée pour évaluer le potentiel des champignons mycorhiziens à arbuscules (CMA) à amélio-rer la résistance du bananier plantain au déficit hydrique. Trois inocula ont été utilisées : (1) une souche de Glomus clavispo-rum provenant d'Azaguié, (2) un complexe de spores isolé provenant d'Azaguié (5 ° 38 'N-4 ° 05' O) et (3) un complexe de spores provenant de Bouaflé (6 ° 59 'N-5 ° 45' O). Ces inocula ont été testés sur les variétés Fhia 21 et Orishele en considé-rant trois niveaux d'apport d'eau (100, 60 et 30%). La croissance des plants et d'autres paramètres physiologiques ont été mesurés et comparés pour tous les traitements. Il en ressort que la colonisation des racines a diminué avec la réduction de l'apport d'eau. Les plants mycorhizés avaient les feuilles les plus larges, la plus grande teneur en eau et en chlorophylle, quel que soit le niveau d'apport en eau. De même, les CMA ont augmenté de manière significative les sucres solubles et les teneurs en proline en condition de déficit hydrique. Ces résultats démontrent que les CMA augmentent l'activité photosyn-thétique du bananier plantain et ont un impact sur sa croissance dans toutes les conditions d'apport en eau. La proline et les sucres solubles sont des molécules sensibles aux conditions de stress hydrique et leur production dans le bananier plan-tain sont améliorées en présence de CMA. Mots clés : champignons mycorhiziens à arbuscules, Côte d'Ivoire, bananier plantain, résistance, stress hydrique. Abstract Résumé
... The data generated are based on literature review, consulting the Scielo, Scopus and Web of Science databases and the following publications: Mukerji & Bhattacharjee (1983), Vestberg et al. (1999), Mangan & Adler (2000), Picone (2000), Carrenho et al. (2001), Varela & Trejo (2001), Suciatmith (2002), Lovelock et al. (2003), Muthukumar et al. (2003), Souza et al. (2003Souza et al. ( , 2013Souza et al. ( , 2016, Uhlmann et al. (2004), Shi et al. (2006), Gavito et al. (2008), Sharda & Rodrigues (2008), Tchabi (2008), Tchabi et al. (2008), Violi et al. (2008), Aguilar-Fernández et al. (2009), Rhatwal & Gandhe (2009), Cuenca & Lovera (2010), Goto et al. (2010), Wang et al. (2010), Sridhar et al. (2011), Stürmer & Siqueira (2011), Arias et al. (2012), Boonlue et al. (2012), Carneiro et al. (2012), da Silva et al. ( , 2015aSilva et al. ( , b, 2017a, de Carvalho et al. (2012), de Mello et al. (2012, Jefwa et al. (2012), Lakshmipathy et al. (2012), Rajkumar et al. (2012), Bonfim et al. (2013Bonfim et al. ( , 2016, Johnson et al. (2013), Kamble et al. (2013), Leal et al. (2013), Pagano et al. (2013), Pontes et al. (2013), Santos et al. (2013), Teixeira-Rios et al. (2013), Vasconcellos et al. (2013), Freitas et al. (2014), Gupta et al. (2014), Pereira et al. (2014Pereira et al. ( , 2016, Sousa et al. (2014Sousa et al. ( , 2017, Belay et al. (2015), Channabasava & Lakshman (2015), Dantas et al. (2015), , Rajeshkumar et al. (2015), Trejo et al. (2015), de Assis et al. (2016), Jobim et al. (2016), Willis et al. (2016), Andrade et al. (2017), Pontes et al. (2017a, b, c), Souza & Freitas (2017), Torres- Arias et al. (2017), Verma & Verma (2017). ...
Tropical forests account for about 50 % of all world biodiversity, playing a key role in the functioning of the globe. These forests are divided into six natural vegetation formations: Lowland evergreen rainforests, Semi-evergreen rainforests, Dry forests, Lower montane forests, Upper montane forests and Mangroves. Arbuscular mycorrhizal fungi (AMF - Glomeromycotina) are among the organisms commonly found and directly related to the balance and functioning of these plant communities. This review shows the record of 228 AMF species in tropical forests, distributed in 14 families and 35 genera, representing 75 % of the known richness of this group of soil fungi. The Dry forests exhibit the largest number of AMF species. Areas under anthropic influence in the various forest formations generally present a decrease in richness when compared to natural preserved areas.
... Calcium and magnesium are the two major metallic elements essential to the growth and productivity of all plants. From the fertility point of view, the exchangeable (Jefwa et al. 2012;Fotso et al. 2016) or available amount of a metallic nutrient (Moreira and Fageria 2009) in soils is significant. However, measurement of the total amount of these metals in soils can reveal the potential for productivity or soil fertility. ...
The present report is a general assessment of the level of nutrient and toxic heavy metals as an impact of Bchemicalized^ cultivation
practices for decades in banana fields in the three south Indian states, Kerala, Karnataka, and Tamilnadu. The major objective was to
critically analyze the status of metallic content in green revolution fields, where chemical fertilizers or plant protective chemicals
remain the major source of heavy metal contaminants. Since soil series being a soil taxonomic category that includes slightly variant
soils of similar origin and common parent materials, the 286 field samples of the broad south Indian region were further grouped into
composite samples representing 47 different soil series for limiting the sample analysis. The quantitative assessment of ten metals
done in these soils using the Atomic Absorption Spectrophotometer included Ca, Mg, Mn, Zn, Fe, Cu, Pb, Ni, Cr, and Co. The
amount of Cu observed in many fields was higher than all the previous reports of the same in the Bchemicalized^ fields. Similarly, the
amount of Co observed in 25 fields was above its threshold levels expected for normal soils. The amount of Pb observed in all the
soils appeared quite normal. The amount of Ni observed in 14 soil series was higher than its threshold levels for normal soils, except in
4 soil series, where its amount exceeded the upper limit of contamination. Cr was detected in all the samples, but found higher than its
threshold level in 31 soil series. Significant positive correlations were observed between the amounts of different metals in the study.
PCA results indicated that variables were correlated to four principal components, and 74.36% of the total variance was justified.
Keywords Banana . Heavy metal contamination . Southern Indian soils . Soil series . Cultivated soils . Green revolution fields
... Significant differences in colonization of banana cultivars by AM fungal isolates were observed (Declerck et al., 1995). In addition, under greenhouse conditions 50-70% root colonization was observed; however under field conditions, it was 37-57% (Jefwa et al., 2012). Plant mycorrhizal dependency and root colonization depend upon several soil and plant factors, as well as AM fungal species (Mwashasha et al., 2011;Ortas and Ustuner, 2014). ...
The objective of this study was to investigate the acclimatization and performance of banana (Dwarf Cavendish) in two substrates inoculated with different AM fungi (Glomus. caledonium and G. macrocarpun) and assess the plantlets dependency on inoculation for phosphorus (P) and zinc (Zn) uptake along with biomass development. In addition, to investigate the role of mycorrhizal fungi in supporting acclimatization phase, a plant growth promotion study was set-up in greenhouse using micropropagated plantlets. Two growth media, as GM-I and GM-II were used accompanied by G. caledonium and G. macrocarpum. In first phase, 9 weeks acclimatization study was conducted and in second phase, acclimatized plants were propagated for 16 weeks in both inoculated and non-inoculated conditions. Plantlets acclimatization and nutrient uptake were recorded along with other parameters. Mycorrhizal inoculation significantly increased banana plantlets growth, root infection and P uptake. Plantlets inoculated with G. caledonium exhibited increase in shoot and root dry mass, P and Zn concentration, and root infection in the GM-I. The shoot and root dry mass, P and Zn concentration, and root infection were higher in GM-I than Konaktas soil series. Banana plantlets are mycorrhizal dependent (MD) and soil-grown banana plantlets are more MD than plants grown in the GM-I. Mycorrhizal inoculation seems to be a significant factor in decreasing mortality and increasing production of high-quality banana plantlets under micropropagation conditions.
Diversity of arbuscular mycorrhizal fungi (AMF) in banana and plantain fields in western Cuba is here reported. Thirty rhizosphere soil samples were collected and used for direct evaluation of the AMF community and establishment of trap cultures. AMF spores were extracted from the soil samples by wet sieving and decanting, and species were identified based on the morphology of the spores. Overall, 56 AMF morphospecies were differentiated within at least 10 genera. From the total number of morphospecies, 25 were identified up to the species level, and 31 were morphologically different from described species. From field samples, 42 morphospecies were verified, with predominance of the genera Acaulospora and Glomus. However, the most frequent species recovered directly from the field samples were Claroideoglomus etunicatum and Funneliformis geosporum. Additionally, 14 morphospecies were only obtained in the trap cultures, from which five could be identified up to the species level while the other nine corresponded to apparently undescribed species. It was concluded that banana and plantain fields in western Cuba have highly diverse communities of arbuscular mycorrhizal fungi.
Phosphorus, nitrogen and Striga hermonthica are the major constraints to maize production in the Nyanza Province of Kenya. Field trials were conducted on-farm in Nyanza Province to investigate the effects of phosphate fertilizers and manure on maize yields. The experimental design was a Randomized Complete Block Design (RCBD) with maize as the test crop. The maize was top dressed with calcium ammonium nitrate (CAN) fertilizer at a uniform rate of 30 kg N/ha diammonium phosphate (DAP), Minjingu rock phosphate (MRP) and triple super phosphate (TSP) fertilizers were applied at 60 kg/ha P2O5, farmyard manure (FYM) at 10 t/ha and a non-phosphorus (P) treatment (control) plus lime only. Responses (P ≤ 0.01) from grain yield, total dry matter yield and harvest index to phosphate fertilizers and manure treatments were found. Nutrient uptake and removal by the crop increased (P ≤ 0.01) due to fertilizers and manure application. Phosphate fertilizers and manure application increased (P ≤ 0.01)) available soil P, agronomic phosphorus use efficiency (APUE) and Physiological P use efficiency (PPUE). The results indicate that phosphate fertilizers and manure applications are essential to improve maize yield and nutrient P use efficiency.
Improving fertilizer recommendations for farmers is essential to increase food security in smallholder landscapes. Currently, blanket recommendations are provided across agro-ecological zones, although fertilizer response and nutrient use efficiency by maize crop are spatially variable. We aimed to identify factors that could help to refine fertilizer recommendation by analyzing the variability in fertilizer response (FR) and the agronomic nitrogen use efficiency (N-AE). A literature search for on-farm studies across Kenya and Sub-Sahara Africa (SSA), excluding Kenya, yielded 71 publications. The variability in FR was studied using a meta-analysis whereas key factors that influence FR and N-AE were studied with linear regression models. On average, the FR was 2, but it varied considerably from 1 to 28.5 (excluding outliers). In SSA, 18% of the plots were non-responsive plots with an FR < 1. The main factors affecting N-AE for Kenya were P-Olsen, silt content, soil pH, clay and rainfall, whereas only soil pH, exchangeable K and texture were important for SSA. However, our study indicates that available data on soil, climate and management factors could explain only a small part (< 33%) of the variation in FR and N-AE. Soil pH, P-Olsen, silt content, and rainfall had significant but low levels of power in explaining variation in FR and N-AE. Our findings indicate that strategies to refine fertilizer recommendation should include information on soil types and soil properties.
Diagnostic on-farm nutrient omission trials were conducted over two cropping seasons (2015 and 2016) to assess soil nutrients related constraints to maize yield in the northern Nigerian savanna agro-ecological zone and to quantify their variability. Two sets of trials were conducted side by side, one with an open pollinated maize variety (OPV) and the other one with a hybrid maize variety and each set had six equal treatments laid out in 198 farmers’ fields. The treatments comprised (i) a control, (ii) a PK (‘−N,’ without N), (iii) an NK (‘−P,’ without P), (iv) an NP (‘−K,’ without K), (v) an NPK and (vi) an NPK + S + Ca + Mg + Zn + B (‘+SMM,’ NPK plus secondary macro- and micro-nutrients). Moderate to a large variability in most soil characteristics was observed in the studied fields. Consequently, cluster analysis revealed three distinct yield-nutrient response classes common for the two types of maize varieties. These define classes were fields that have (i) no-response to any nutrient, (ii) a large response to N and P and (iii) a large response to N alone. Although overall yield performance of OPV and hybrid varieties was similar, a distinct fourth class was identified for the hybrid variety, (iv) fields with a large response to N and secondary macro- and micro-nutrients. The results indicate that the large variability in soil nutrients related constraints need to be accounted for to optimize maize yield in the northern Nigerian savanna. The development of field- and area-specific fertilizer recommendations is highly needed, using simple decision support tools that consider variable soil fertility conditions and yield responses as obtained from this study.
The coefficient of determination R² quantifies the proportion of variance explained by a statistical model and is an important summary statistic of biological interest. However, estimating R² for generalized linear mixed models (GLMMs) remains challenging. We have previously introduced a version of R² that we called for Poisson and binomial GLMMs, but not for other distributional families. Similarly, we earlier discussed how to estimate intra-class correlation coefficients (ICCs) using Poisson and binomial GLMMs. In this paper, we generalize our methods to all other non-Gaussian distributions, in particular to negative binomial and gamma distributions that are commonly used for modelling biological data. While expanding our approach, we highlight two useful concepts for biologists, Jensen's inequality and the delta method, both of which help us in understanding the properties of GLMMs. Jensen's inequality has important implications for biologically meaningful interpretation of GLMMs, whereas the delta method allows a general derivation of variance associated with non-Gaussian distributions. We also discuss some special considerations for binomial GLMMs with binary or proportion data. We illustrate the implementation of our extension by worked examples from the field of ecology and evolution in the R environment. However, our method can be used across disciplines and regardless of statistical environments.
Sustainability of maize-based cropping systems is a major challenge for southern Africa, yet the demand for maize as staple food and animal feed in the region continues to increase. A study was conducted on a sandy clay loam (220 g clay kg⁻¹ soil) at Domboshawa in Zimbabwe to investigate the long-term effects of organic resource quality and application rate, and nitrogen (N) fertilization on soil chemical properties and maize (Zea mays L.) productivity. Crotalaria juncea (high quality), Calliandra calothyrsus (medium quality), cattle manure (variable quality), maize stover and Pinus patula sawdust (both low quality) were incorporated into soil at 4.0 t C ha⁻¹ (high rate) and 1.2 t C ha⁻¹ (low rate) at the start of each cropping season for nine consecutive years. At both high and low application rates, each of the five organic resources was applied in combination with or without mineral nitrogen (N) fertilizer at 120 kg N ha⁻¹. The nine-year period saw maize grain yields declining by 22% to 84% across treatments despite increases in soil organic carbon, total N and available P from 6% to 80%. Crotalaria, Calliandra and manure led to a less steep yield decline. Exchangeable calcium (Ca), magnesium (Mg) and potassium (K), and soil pH explained much of the variation in yield patterns observed under the different organic resource applications. Maize grain yield was positively correlated with exchangeable Ca (r = 0.51), Mg (r = 0.62) and K (r = 0.53), and soil pH (r = 0.49), but negatively correlated with other soil properties over the 9-year period. We concluded that declining soil exchangeable basic cations were the underlying causes of decreasing maize productivity, and was aggravated by use of low rates of organic resource inputs, particularly with N fertilization. Current nutrient management and fertilizer recommendations that emphasize inorganic N, P and K significantly undervalue the role played by organic resources in sustainability of maize cropping systems in southern Africa. © 2017 Mtangadura et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Soil, a natural four-dimensional body at the atmosphere–lithosphere interface, is organic-carbon-mediated realm in which solid, liquid, and gaseous phases interact at a range of scales and generate numerous ecosystem goods and services. Soil organic carbon (SOC) strongly impacts soil quality, functionality and health. Terms soil quality and soil health should not be used interchangeable. Soil quality is related to what it does (functions), whereas soil health treats soil as a living biological entity that affects plant health. Through plant growth, soil health is also connected with the health of animals, humans, and ecosystems within its domain. Through supply of macro- and micronutrients, soil health, mediated by SOC dynamics is a strong determinant of global food and nutritional security. Soil C pool consists of two related but distinct components: SOC and soil inorganic C (SIC). The SIC pool comprises of primary and secondary carbonates, and the latter consists of calcitic (no net sequestration of atmospheric CO2) and silicatic (net sequestration). While SOC is highly dynamic, its mean residence time depends on the degree of protection (physical, chemical, biological, and ecological) within the soil matrix. Formation of stable microaggregates and of organo–mineral complexes can protect SOC against microbial processes for millennia. In addition to formation of silicatic type of secondary carbonates, leaching of bicarbonates into the subsoil or shallow water table is also an important mechanism of sequestration of CO2 as SIC. Numerous soil functions and ecosystem services depend on SOC and its dynamics. Improvements in soil health, along with increase in availability of water and nutrients, increases soil's resilience against extreme climate events (e.g., drought, heat wave) and imparts disease-suppressive attributes. Enhancing and sustaining soil health is also pertinent to advancing Sustainable Development Goals of the U.N. such as alleviating poverty, reducing hunger, improving health, and promoting economic development.
Spatial distribution of soil nutrients is not normally considered for smallholder farms in Ghana resulting in blanket fertilizer application which leads to low efficiencies of some applied nutrients. This study focuses on applying geospatial analyses to map 120 maize farms in 16 districts of the Northern region of Ghana to identify nutrient distribution. Soil samples were taken from these 120 locations and analysed for contents of nitrogen (N), phosphorus (P) and potassium (K). Spatial models of the contents were generated through geostatistical analysis to map the status of N, P and K nutrients across the locations. Study results indicated that proportion of area deficient in N is 97%, P is 72% and K is 12%. Distribution pattern for N and K nutrients were clusters of low or high contents at specific locations; and that of P was random. Outcome of this study could enhance site-specific nutrient recommendation in Ghana.
Soil Organic Carbon (SOC) is a major indicator of soil fertility in the tropics and underlies variability in crop response to mineral fertilizers. Critical SOC concentrations that interact positively with N fertilizer for optimal crop yield are less understood. A study was conducted on a Ferralsol in sub-humid Uganda to explore the critical range of SOC concentrations and associated fractions for optimal maize (
Zea mays
L.) yield response to applied mineral N fertiliser. Maize grain yield response to N rates applied at 0, 25, 50 and 100 kg N ha
−1
in 30 fields of low fertility (SOC
<
1.2%), medium fertility (SOC = 1.2–1.7%) and high fertility (SOC
>
1.7%) was assessed. Soil was physically fractionated into sand-sized (63–2000 µm), silt-sized (2–63 µm) and clay-sized (<2 µm) particles and SOC content determined. Low fertility fields (<1.2% SOC) resulted in the lowest response to N application. Fields with >1.2% SOC registered the highest agronomic efficiency (AE) and grain yield. Non-linear regression models predicted critical SOC for optimal yields to be 2.204% at the 50 kg N ha
−1
rate. Overall, models predicted 1.9–2.2% SOC as the critical concentration range for high yields. The critical range of SOC concentrations corresponded to 3.5–5.0 g kg
−1
sand-sized C and 9–11 g kg
−1
for clay-sized C.
Bananas and plantains are cultivated in over 100 countries throughout the tropical and sub-tropical regions of the world. They are grown over a harvested area of approximately 10 million hectares, with an annual production of around 88 million metric tonnes, of which approximately one third is produced in each of the African, Asia-Pacific and Latin America and Caribbean regions. The vast majority of producers are small-scale farmers growing the crop either for home consumption or for local markets.
Details are given for each region.
Crop association with arbuscular mycorrhizal fungi (AMF) often prove beneficial to crop productivity through a number of mechanisms, such as improved access to nutrients and water and pest and disease suppression. Banana and plantain (Musa spp.) are both mycorrhizal plants, with a number of studies demonstrating the strong stimulatory effect of AMF on plant growth in pots. Therefore, application of AMF to newly deflasked tissue culture plants or in nurseries may improve plant growth and possibly provide healthier plants for sale to farmers. Pot trials have also shown that inoculated plants are better able to suppress nematodes. However, how this association benefits banana and plantain plant performance under field conditions remains largely unknown. Studies are currently underway to determine the mycorrhizal associations of banana and plantain cultivars with AMF in East and Central Africa. Greenhouse studies complement field studies for comparison at the different levels. In West Africa, studies have been conducted to assess AMF association and yield impact following inoculation. Data from across Africa increasingly highlights that composition and abundance of AMF species associated with Musa spp. is highly variable. Up to 20 AMF species were found to be associated with banana plantations in East and Central Africa. Spore abundance, the inoculum reservoir that determines colonization, is largely influenced by management practices. The data generated to date increasingly illustrates the importance of AMF in banana systems and its sensitivity to crop and soil management practices. Some AMF species appear to be better than others with regard to their effects on banana growth, nutrient uptake and control of root damage by nematodes. Studies are in progress to screen AMF species and establish trials along different integrated soil fertility management practices. This paper summarizes the state-of-the-art regarding our knowledge of AMF and its (potential) impact on banana and plantain production in Africa.
80% of arable land in Africa has low soil fertility and suffers from physical soil problems. Additionally, significant amounts of nutrients are lost every year due to unsustainable soil management practices. This is partially the result of insufficient use of soil management knowledge. To help bridge the soil information gap in Africa, the Africa Soil Information Service (AfSIS) project was established in 2008. Over the period 2008-2014, the AfSIS project compiled two point data sets: the Africa Soil Profiles (legacy) database and the AfSIS Sentinel Site database. These data sets contain over 28 thousand sampling locations and represent the most comprehensive soil sample data sets of the African continent to date. Utilizing these point data sets in combination with a large number of covariates, we have generated a series of spatial predictions of soil properties relevant to the agricultural management-organic carbon, pH, sand, silt and clay fractions, bulk density, cation-exchange capacity, total nitrogen, exchangeable acidity, Al content and exchangeable bases (Ca, K, Mg, Na). We specifically investigate differences between two predictive approaches: random forests and linear regression. Results of 5-fold cross-validation demonstrate that the random forests algorithm consistently outperforms the linear regression algorithm, with average decreases of 15-75% in Root Mean Squared Error (RMSE) across soil properties and depths. Fitting and running random forests models takes an order of magnitude more time and the modelling success is sensitive to artifacts in the input data, but as long as quality-controlled point data are provided, an increase in soil mapping accuracy can be expected. Results also indicate that globally predicted soil classes (USDA Soil Taxonomy, especially Alfisols and Mollisols) help improve continental scale soil property mapping, and are among the most important predictors. This indicates a promising potential for transferring pedological knowledge from data rich countries to countries with limited soil data.
Low crop yields in the savannah zones of West Africa are commonly attributed to rainfall deficits and poor soil fertility. In this study, an assessment was made on how the position of fields belonging to different farm types can explain soil variability and related crop yield gaps in two villages in Burkina Faso, Yilou and Koumbia, located, respectively, in the Sudano-Sahelian and Sudanian agro-ecological zones. In each village, four farm types were identified. Soil fertility was generally poor and use of nutrient inputs low in most of the farmer’s fields . As a consequence, yields for most crops were low, but differences among farm types were found, which can be linked to their socioeconomic characteristics that influence the amount of inputs used. Application of fertilizers differed also between fields within farms and tended to be greater on the fields near the homesteads in the village of Yilou, especially for organic fertilizers. At both villages, the rates of N and K inputs were insufficient to compensate for their respective output rates, leading to negative partial nutrient balances . The existence of patchworks of soil fertility gives rise to a wide variation in crop responses to fertilizers. Exploitable yield gaps were substantial and to a large extent related to the low fertility status of soils and sub-optimal fertilizer applications.
Degradation of land health - the capacity of land, relative to its potential, to sustain delivery of ecosystem services - is recognized as a major global problem in general terms, but remains poorly quantified, resulting in a lack of specific evidence to focus action. Land health surveillance and response is designed to overcome limitations of current assessment approaches. It is modelled on science principles and approaches used in surveillance in the public health sector, which has a long history of evidence-informed policy and practice.
This study examines current land access and livelihood choices of rural youth in Southern Ethiopia. We found that youth in rural south have limited access to agricultural land because of land scarcity and land market restrictions. We hypothesize that this forces the youth to abandon agriculture in search of other livelihoods. Our study shows that only 9% of the rural youth plan to pursue agriculture as their livelihood. We also found a sharp increase in youth outmigration in the past six years. Our econometric analyses confirm that lack of land access is forcing the youth away from an agricultural livelihood.
Maximum likelihood or restricted maximum likelihood (REML) estimates of the
parameters in linear mixed-effects models can be determined using the lmer
function in the lme4 package for R. As for most model-fitting functions in R,
the model is described in an lmer call by a formula, in this case including
both fixed- and random-effects terms. The formula and data together determine a
numerical representation of the model from which the profiled deviance or the
profiled REML criterion can be evaluated as a function of some of the model
parameters. The appropriate criterion is optimized, using one of the
constrained optimization functions in R, to provide the parameter estimates. We
describe the structure of the model, the steps in evaluating the profiled
deviance or REML criterion, and the structure of classes or types that
represents such a model. Sufficient detail is included to allow specialization
of these structures by users who wish to write functions to fit specialized
linear mixed models, such as models incorporating pedigrees or smoothing
splines, that are not easily expressible in the formula language used by lmer.
Heterogeneity in soil fertility in these smallholder systems is caused by both inherent soil-landscape and human-induced variability across farms differing in resources and practices. Interventions to address the problem of poor soil fertility in Africa must be designed to target such diversity and spatially heterogeneity. Data on soil management and soil fertility from six districts in Kenya and Uganda were gathered to understand the determinants of soil heterogeneity within farms. Analysis of the variance of soil fertility indicators across 250 randomly selected farms (i.e., 2607 fields), using a mixed model that considered site, sampling frame, farm type, and field as random terms, revealed that the variation in soil organic C (6.5-27.7 g kg(-1)), total N (0.6-3.0 g kg(-1)), and available P (0.9-27 mg kg(-1)) was mostly related to differences in the inherent properties of the soils across sites (50 to 60% of total variance). Exchangeable K+ (0.1-1.1 cmol((+)) kg(-1)), Ca2+ (1.5-14.5 cmol((+)) kg(-1)), Mg2+ (0.6-3.7 cmol((+)) kg(-1)), and pH (5.1-6.9) exhibited larger residual variability associated with field-to-field differences within farms (30 to 50%). Soil fertility indicators decreased significantly with increasing distance from the homesteads. When this variable was included in the model, the unexplained residual variances-associated with soil heterogeneity within farms-were 38% for soil C; 32% for total N; 49% for available P; 56, 49, and 38% for exchangeable K+, Ca2+ and Mg2+, respectively; and 49% for the pH. In allocating nutrient resources, farmers prioritized fields they perceived as most fertile, reinforcing soil heterogeneity. Categorization of fields within a farm with respect to distance from the homestead, and soil fertility classes as perceived by farmers, were identified as entry points to target soil fertility recommendations to easily recognizable, distinct entities.
Avocado trees lack root hairs. It has been demonstrated that arbuscular mycorrhiza forming fungi (AMF) colonize these fruit trees, favour water absorption and nutrient uptake by plants, and also enhance growth and ameliorate plant health. However, the symbiotic associations in the field and the role AMF may play on the production system are not currently well documented; approaches on mycorrhizal symbiosis and its yield effects have been mainly addressed to plant nursery as well as to in vitro propagation. This caused the present study, which aims at determining AMF diversity and abundance on avocado orchards soil in Michoacan, Mexico. The experiment was developed in orchards with seven different climates, under two moisture conditions (irrigation and rain fed) and in two times of the year (rainy and low water season). Rhizosphere samples were obtained from soils of 14 orchards; spores from those samples were extracted and mounted on glass slides to identify and quantify them under microscope. 22 morphospecies corresponding to five genera, from three families and two orders, were identified; seven of them had not been previously reported as associated with the avocado culture. In the low water season species, distribution of the three genera was as shown: Glomus (39.43%), Acaulospora (26.23%) and Scutellospora (21%) and while in the rainy season the distribution among these genera differed: Glomus (37.56%), Scutellospora (29.16%) and Acaulospora (23.24%).
p>Large variability in crop responses to macronutrient application at various spatial scales present challenges for developing effective fertilizer recommendations for crop production in smallholder farming systems of sub-Saharan Africa. We assessed maize yield responses to nitrogen (N), phosphorus (P) and potassium (K) application and evaluated relationships between crop responses to N, P and K application and soil analysis data. Nutrient omission trials were conducted on 23 farms located in Sidindi, Western Kenya, selected to be representative of the main soil and management factors in maize based systems in Siaya County. Treatments included a control and PK, NK, NP and NPK applications. The trials ran for six consecutive cropping seasons, without changing treatments or plot location, covering the period 2013–2015. Strong spatial-temporal patterns in maize yield responses to N, P and K applications were observed. Average maize yields in the control, PK, NK, NP and NPK treatments were 2.8, 3.2, 5.1, 5.1 and 5.5 t ha<sup>−1</sup> at 88% dry matter respectively in the first cropping season, and 1.1, 1.4, 2.9, 3.6 and 5.3 t ha<sup>−1</sup> at 88% dry matter respectively in the sixth cropping season. In all seasons, variability in maize yield between fields was greatest in the control treatment followed by the NK treatment and least in the NPK treatment. Mean relative yield was 0.6, 0.92 and 0.93 for N, P and K respectively, in the first cropping season, and 0.25, 0.52 and 0.68, respectively, in the sixth cropping season. Six main maize yield response categories were identified that differed in the maize grain yield responses to recursive N, P and K applications. Maize yield responses to N, P and K were not fully accounted for by soil organic matter, soil available P and exchangeable K respectively. Our results indicate that current methods for soil analysis do not adequately predict the response to application of N, P and K fertilizer under the highly variable soil fertility conditions encountered in smallholder farming systems. The strong spatial-temporal patterns observed present major challenges for the development of effective site-specific fertilizer recommendations. Potential avenues for future research and options for more effective intensification strategies are discussed.</p
A poor response to fertilizer application is one of the persisting constraints preventing closure of the maize yield gaps in Sub-Saharan Africa (SSA). It is speculated that nutrient imbalances derived from deficient and/or excessive concentrations could be one of the causes of this limited response of maize to fertilizer. This is however not confirmed and the extent of such poor response is ill-documented. To investigate this, we conducted 44 on-farm trials with a two treatment structure (with and without NPK fertilizer) in two subsequent seasons, the 2014 long rains (LR) and short rains (SR) distributed across two sites: Bungoma-Southwest and Busia-North in western Kenya. As a discriminating criterion between responsive and poorly responsive soils, we used a Value Cost Ratio (VCR) of 2 of NPK fertilizer use. Nutrient sufficiency ranges were developed using compositional nutrient diagnosis (CND method) and then used to identify both deficient and/or excessive nutrient concentrations occurring in maize grown in the poorly responsive soils.
Results show that 48% of all fields from both sites could be classified as ‘poorly responsive’, with small VCR values ranging between 0.1 and 1.99. Nutrient deficiencies were more prevalent than situations of excessive concentrations in such fields. N-deficiency was the most common in the unfertilized (control) plots occurring in between 80 and 89% of the poorly responsive plots. Zn-deficiency became apparent in the fertilized plots and was observed at similar frequencies in this treatment. The next most widespread nutrient deficiencies in poorly responsive soils were those of P and Cu affecting between 70 and 79% of both control and fertilized plots. K and Mg deficiencies were rare in both treatments. This study indicates that the occurrence of poorly responsive soils in Bungoma-southwest and Busia-North is likely related to micronutrient deficiencies. These findings necessitate further investigation on the bioavailability of these micronutrients nutrients in such soils and a validation trial to evaluate the extent of crop responses.
Significance
Improvements in agricultural productivity in developing countries are thought to play a key role in poverty reduction. Unfortunately, such productivity remains poorly measured throughout much of the world, hampering efforts to evaluate and target productivity-enhancing interventions. Using high-resolution satellite imagery in combination with field data we collected from thousands of smallholder plots in Kenya, we show that satellite imagery can be used to estimate and understand yield variation at the field scale across African smallholders. Our results suggest a range of potential capabilities, including the inexpensive measurement of the impact of specific interventions, the broader characterization of the source and magnitude of yield gaps, and the development of financial products aimed at African smallholders.
Micropropagation has established its position as a way of propagating large numbers of uniform plants. For some plant species that are difficult to propagate by seeds or by conventional cuttings, this technique provides the only possible way of producing high quality plants. Micropropagation is widely used for propagation of high value crops like ornamentals, fruits, vegetables, plantation crops and spices (Vestberg and Estaún 1994). The micropropagation industry was growing fast in Europe up to 1992 (O’Riordain 1992) but after that the micropropagation industry seems to have stabilized its position although a slight increase in production of microplants was still recorded for the period 1993-1996 (O’Riordain 2000). Prunus is the most important plant in both commercial and official laboratories (O’Riordain 2000).
Land health surveillance is a methodological framework for measuring and monitoring land health—the capacity of land to sustain delivery of ecosystem services—for the purpose of targeting agroforestry and other sustainable land management in landscapes, and assessing their impacts. It is modelled on scientific principles used in surveillance in the public health sector, which has a long history of evidence-informed policy and practice. Key elements of the science methodological framework are (1) probability-based sampling of well-defined populations of sample units; (2) standardized protocols for data collection to enable statistical analysis of patterns, trends, and associations; and (3) multilevel statistical modelling of land health attributes at different scales, including in relation to satellite imagery for spatial interpolation. The framework was applied in assessing soil carbon in Kenyan rangelands in Laikipia. Systematic probability-based field sampling provided a robust baseline on condition in the study area. Infrared spectroscopy was used in the laboratory as a rapid low-cost tool for estimating soil carbon concentration. The georeferenced soil carbon values were modelled to reflectance values of fine resolution (2 m) satellite imagery and spatially interpolated over the 100-km2 sampling block. The combination of methods makes soil carbon baselines feasible at a landscape level in land management projects and provides much additional information on soil and vegetation health for targeting interventions. The land health surveillance approach could form the basis for evidence-based decision making on land management at project, national, and even continental levels.
Seventeen Musa cultivars that were rated highly by the small-scale farmers in Kenya were examined for random amplified polymorphic DNA (RAPD) genetic markers using PCR with ten 10-mer primers. The aim of the study was to sort out synonyms and enable in vitro production of true-to-type plants. The study included five reference cultivars of genomic groups AA, AB, AAA, AAB, and ABB to uncover the genomic groups prevalent among the Kenyan cultivars. The ten primers generated 69 genetic markers that were used for estimation of genomic groups and for cultivar identification. Pairwise RAPDistance analysis of the data and subsequent generation of a dendrogram using the "Neighbour Joining Tree" program grouped the cultivars into two major clusters depending on their genomic similarities. One cluster comprised the Kenya highland bananas that grouped with the AAA reference cultivar Poyo, while the other cluster contained the coastal lowland cultivars that grouped with the ABB AAB and AB reference cultivars Saba, Kelong Mekindu, Safet Velchi, respectively. The dissimilarity analysis between the samples showed no duplication among the banana accessions. Each cultivar was genotypically different although some were closely related.
Using eight nuclear and four chloroplast microsatellite markers, a total of 133 banana (Musa spp.) accessions from East Africa, Bioversity International and Polynesia were characterized at the University of Hawaii. The objectives of the study were to determine variation patterns existing in the Musa AA and AAB genomes of East Africa and to determine the usefulness of microsatellites markers in differentiating accessions within the two Musa genome groups. Group average clustering produced major clusters corresponding to the genome composition of AAA, AAA-EA, AAB (plantains), AAB (dessert bananas), AA and AB. At least four distinct subclusters of 'Apple Banana' (AAB genome) were observed, namely 'Mysore' (AAB genome), 'Sukari Ndizi' (AAB geome), 'Prata' (AAB genome) and 'Silk' (AAB genome). The East African 'Muraru' (AA genome) dessert bananas formed a distinct cluster with a high similarity to AAA dessert bananas, suggesting the possibility of shared ancestry between them.
As soils are facing considerable changes in climate, land use, land consumption, and degradation, it is vital to understand the characteristics of soils and their distribution, especially for soil management issues. In mountainous regions like the Alps, soils require specific attention as they provide a large variety of ecological functions, but also because of their vulnerability. However, pedological research and the collection of soil data in the Alps are still limited. On the one hand, there are specific methodological problems linked to the surveying, interpretation, and classification of Alpine soils due to their high variability over short spatial ranges and the peculiarities of the Alpine environment in general. On the other hand, the process of collecting soil data and mapping soils, as well as the soil classification systems used, significantly differs among the Alpine countries. The Alpine Convention therefore requires data harmonization as a basis for national and cross-country collaborations, soil monitoring, and sustainable management.
Although Typha (cattail) species have been reported to be non-mycorrhizal, recent studies have reported arbuscular mycorrhizal (AM) structures in Typha roots, even in very wet habitats. The purpose of this study was to determine the relationship between phosphorus availability and AM colonization of Typha angustifolia. Typha angustifolia was grown in factorial combinations of four phosphorus concentrations (1, 10, 100, and 500 μm P) and two inoculum densities (200 or 500 spores/pot), with an uninoculated control treatment at 100 μm P. After 13 wk, AM colonization was present in the three lowest phosphorus treatments, but was absent from the 500 μm P and control treatments. Colonization did not differ significantly between inoculum density treatments. Shoot dry mass increased significantly with increased phosphorus and was marginally higher in treatments that received 200 spores than 500 spores. Among the 100 μm P treatments, shoot dry mass was significantly higher in the 200 spore treatment than the uninoculated control, but shoot nutrient content did not differ. This study presents clear evidence that AM fungi can colonize T. angustifolia under controlled conditions as a function of phosphorus availability.
[1] Often hydrologic regression models are developed with ordinary least squares (OLS) procedures. The use of OLS with highly correlated explanatory variables produces multicollinearity, which creates highly sensitive parameter estimators with inflated variances and improper model selection. It is not clear how to best address multicollinearity in hydrologic regression models. Here a Monte Carlo simulation is developed to compare four techniques to address multicollinearity: OLS, OLS with variance inflation factor screening (VIF), principal component regression (PCR), and partial least squares regression (PLS). The performance of these four techniques was observed for varying sample sizes, correlation coefficients between the explanatory variables, and model error variances consistent with hydrologic regional regression models. The negative effects of multicollinearity are magnified at smaller sample sizes, higher correlations between the variables, and larger model error variances (smaller R2). The Monte Carlo simulation indicates that if the true model is known, multicollinearity is present, and the estimation and statistical testing of regression parameters are of interest, then PCR or PLS should be employed. If the model is unknown, or if the interest is solely on model predictions, is it recommended that OLS be employed since using more complicated techniques did not produce any improvement in model performance. A leave-one-out cross-validation case study was also performed using low-streamflow data sets from the eastern United States. Results indicate that OLS with stepwise selection generally produces models across study regions with varying levels of multicollinearity that are as good as biased regression techniques such as PCR and PLS.
Understanding the patterns of land degradation indicators can help to identify areas under threat as basis for designing and implementing site-specific management options. This study sort to identify and assess the patterns of land degradation indicators in selected districts of western Kenya. The study employed the use of Land Degradation Sampling Framework (LDSF) to characterize the sites. LDSF a spatially stratified, random sampling design framework consisting of 10 km × 10 km blocks and clusters of plots. The study broadly identified and classified the indicators and attributes of land degradation into soil and site stability, hydrologic function and biotic integrity. Assessment of general vegetation structure showed that over 70% of the land was under cropland with forests accounting for 8% of the area. Sheet erosion was the major form of soil loss. High variability was observed for the soil properties and this can be due to both inherent soil characteristics as well as land management practices. There was distinct variation in the soil properties between the topsoil (0–20 cm) and the subsoil (20–30 cm) with the topsoil having higher values for most of the parameters compared to the subsoil. Using coefficient of variation (CV) as criteria for expressing variability, Ca, TON, Mg, SOC and silt were most variable soil properties for the 0–20 cm depth. Moderate variability (CV 0.15–0.35) was observed for CEC, P, K and clay while Na, Sand and pH had the least variability (CV < 0.15). For the subsoil (20–30 cm), Ca, Mg and silt were the most variable. About 94% of the farms sampled were recorded to have very strongly acidic soil levels (pH 4.5–5.5) while 6% of the farms had moderately acidic soil levels (pH 5.6–6.0). Over 55% of the farms had low (< 2%) total organic carbon levels and this varied with land use. Soils with SOM below this ‘critical level’ are at a threat of degradation if not well managed. The principal component analysis (PCA) identified three main explanatory factors for soil variability: ‘soil fertility potential’, ‘soil physical properties’ and ‘available P’. Improving productivity of land therefore calls for the adoption of integrated soil fertility management (ISFM) options as a strategy to ensuring nutrient availability while at the same time building the natural nutrient reserve through soil organic matter build up.
Sub-Sahara Africa can overcome the soil fertility depletion that has resulted from decades of nutrient mining by small-scale farmers and threatens the region's food security. Nutrient restoration is now technically feasible because its mechanisms are understood and the rural development community is alerted to this need. Rapid and inexpensive approaches of diagnosing soil fertility limitations are also becoming available and information generated is becoming systematically applied. For example, the recently initiated Africa Soil Information Service project aims at evaluating, mapping, and monitoring Africa's soil qualities for better targeting of soil fertility management technologies to improve crop yields while enhancing the environment. Practical knowledge is available on nutrient management in small-scale farming systems that combines increased biological nitrogen fixation, utilizes agromineral resources such as phosphate rock, better uses organic resources, and more efficiently applies mineral fertilizers. The new approach to managing soil nutrients, recognized as integrated soil fertility management, aims to increase food production through strategic combination of traditional and new technologies and is being stimulated through increased availability and more profitable use of mineral fertilizers by Africa's poorer farmers. This is building on already existing sparks of hope for restoring soil fertility in sub-Saharan Africa derived from such examples as the increasing adoption of the zaï-type of pitting system originated in drier parts of West Africa which exemplifies the beneficial effects of integrating harvesting of water and applying nutrient sources at each planting station so as to increase yield in a region where both necessities are key limiting factors. Nitrogen fixation by indigenous and introduced legumes combined with improved agronomic practices has shown potential for kick-starting self-multiplying improvements in soil productivity. Such successes will be accelerated by broader initiatives which improve rural infrastructure, increase accessibility of inputs, improve marketing facilities, and make reinvestment into farming more productive and sustainable. Indeed, experience indicates that investments in farming and, by inference, soil fertility conservation are made when economic returns from smallholder production are sufficient to do so. So, while technical advances leading to improvements in farming practice must continue, policymakers must also recognize that agriculture ultimately forms the basis for economic recovery and act upon past promises to invest in agriculture, including the restoration of nutrient-depleted soils. Investments must address factors that have impacts both on the broad reforms for provision of services such as marketing and trade, as well as those directly constraining the poor farmers such as capacity to access and efficiently apply fertilizers.
The use of partial least squares (PLS) for handling collinearities among the independent variables X in multiple regression is discussed. Consecutive estimates $({\text{rank }}1,2,\cdots )$ are obtained using the residuals from previous rank as a new dependent variable y. The PLS method is equivalent to the conjugate gradient method used in Numerical Analysis for related problems.
To estimate the “optimal” rank, cross validation is used. Jackknife estimates of the standard errors are thereby obtained with no extra computation.
The PLS method is compared with ridge regression and principal components regression on a chemical example of modelling the relation between the measured biological activity and variables describing the chemical structure of a set of substituted phenethylamines.
Dry combustion analysis of carbon (C) and nitrogen (N) in materials of biological or mineral origin is safer and less labor-intensive than traditional acid digestion methods, and can give better recoveries of both elements. Dry combustion macro-analyzers have recently been developed, which allow a sample size of up to several grams to be analyzed for C and N, thereby further increasing the precision and accuracy of these determinations. One of these macro-analyzers, the Leco CN-2000 is a dedicated C and N analyzer, and hence, unlike its companion instrument the Leco CNS-2000, can be finely controlled to maximize the recoveries of organic and inorganic C and N. As yet, though, the combustion temperatures and oxygen flow-rates necessary for optimizing the recoveries of C and N from soil have not been determined for this instrument. Two separate combustion conditions (profiles) were therefore sought for the Leco CN-2000, one of which would minimize the decomposition of carbonate C while maximizing the recovery of organic C (Profile 1), and another one which would maximize the recoveries of total C and total N (Profile 2). Both of these profiles were successfully defined for the instrument. Under lower temperature (1040°C) conditions (Profile 1), the decomposition loss of carbonate from samples of pure CaCO3 was minimized to only one third of the minimum value previously found using the Leco CNS-2000 (1000°C). The measured values for organic C obtained under these conditions were in good agreement with the certified or ‘true’ values for a wide range of reference soils. Nitrogen recovery, however, was sub-optimal under these lower temperature conditions (Profile 1), and indeed for many soils was less than 70% of its potential total. Under the higher temperature (1300°C) conditions (Profile 2), up to 98% of carbonate C was recovered from samples of pure CaCO3, and good agreement was obtained between measured and certified values for total C and total N in a wide range of reference soils. It was concluded that a combustion temperature of 1300°C was essential for making accurate determinations of total C and total N in soil, and that measurements of organic C made using the Leco CN-2000 are, inherently, more accurate and precise than those made using the Leco CNS-2000.
The objectives of this study were to modify the Mehlich 2 (M2) extractant to include Cu among the extractable nutrients, retain or enhance the wide range of soils for which it is suitable and minimize it's corrosive properties. The substitution of nitrate for chloride anions and the addition of EDTA accomplished those objectives. The new extracting solution, already designated Mehlich 3 (M3) is composed of 0.2N CH3COOH‐0.25N NH4N03‐0.015NNH4F‐0.013NHN03‐0.001M EDTA. Extractions from 105 soils using M3, M2, Bray 1 (Bl) and Ammonium Acetate (AA) were compared to evaluate the new extractant. The quantity of F extracted by M3 exceeded that by M2 20% and that by Bl 4% but the results from all extractions were highly correlated. Extractions of both K and Mg by M3 were 6–8% higher than those by AA and 3–4% higher than those by M2, but, again, there was high correlation among methods. Addition of EDTA increased Cu extractions by 170%, Mn by 50% and Zn by 25%. Cu extractions by M3 correlated with those from the Mehlich‐Bowling method. High correlations between Mn, as well as Zn, extracted by M3 and M2 were shown.
Previously described methods to quantify the proportion of root length colonized by vesicular-arbuscular (VA) mycorrhizal fungi are reviewed. It is argued that these methods give observer-dependent measures of colonization which cannot be used to compare, quantitatively, roots examined by different researchers. A modified method is described here to estimate VA mycorrhizal colonization on an objective scale of measurement, involving inspection of intersections between the microscope eyepiece crosshair and roots at magnification × 200; it is referred to as the magnified intersections method. Whether the vertical eyepiece crosshair crosses one or more arbuscules is noted at each intersection. The estimate of colonization is the proportion of root length containing arbuscules, called the arbuscular colonization (AC). The magnified intersections method also determines the proportion of root length containing vesicles, the vesicular colonization (VC), and the proportion of root length containing hyphae, the hyphal colonization (HC). However, VC and HC should be interpreted with caution because vesicles and hyphae, unlike arbuscules, can be produced in roots by non-mycorrhizal fungi.
The effect of an in vitro monoxenically produced arbuscular mycorrhizal fungus (AMF), i.e. Glomus intraradices on the growth and phosphorus content of micropropagated banana (Musa spp. c.v. Grand Naine) plantlets was investigated in a pasteurized and non-pasteurized Vertisol. The experiment was conducted as a 2×2 randomly factorial design with the Vertisol pasteurized or non-pasteurized and the plants inoculated or non-inoculated with the AMF. The plants colonized by AMF had larger shoot and root dry weight and P content than the non-mycorrhizal plants. The largest growth increment was observed in the plants inoculated during the weaning phase with the monoxenic AMF inoculum and subsequently grown in the pasteurized soil. The native AMF population also induced a marked increase in plant growth supporting further the efficiency of this natural population, whereas both inoculum sources in combination did not yield the largest growth increment. The latter suggests a competitive phenomenon between the introduced AMF and the other soil micro-organisms including the native AMF population. Our results demonstrate, for the first time, the potential benefits of a monoxenically produced AMF in micropropagated banana plants.
Summary
In vitro coculture of plant tissue explants with beneficial microorganisms induces developmental and metabolic changes in the derived
plantets which enhance their tolerance to abiotic and biotic stresses. The induced resistance response caused by the inoculants
is referred to as “biotization.” There is enough experimental evidence with bacteria (bacterization) and vesicular arbuscular
mycorrhiza (mycorrhization) inoculations to recommend utilization of this technology in commercial micropropagation. The paper
reviews literature on this topic, outlines other uses and potential uses ofin vitro plant-microbial cocultures, and discusses their current constraints.