Article

Biological control of postharvest green mold decay of oranges by Rhodotorula glutinis

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Abstract

The biocontrol activity of Rhodotorula glutinis on green mold decay of oranges caused by Penicillium digitatum was investigated in vitro and in vivo. Significant control was achieved with a washed cell suspension and an unwashed cell culture mixture of R.glutinis. Treatment of wounds with autoclaved cell cultures or cell-free culture filtrate did not prevent decay. The protection provided by the washed yeast cells was dose-dependent. The higher the concentration of R.glutinis, the better the effect of the biocontrol capacity. At concentrations of yeast of 1109colony-forming units per milliliter or higher and pathogen spore suspensions of 5104spores per milliliter, green mold was almost inhibited after 4-days incubation at 20C. The interval between the pathogen inoculation and the antagonist application significantly influenced the biocontrol ability. The biocontrol efficacy of R.glutinis applied before the pathogen was better than that of applied after the pathogen. Surprisingly, R.glutinis was also effective in controlling green mold at low temperature (4C). Rapid colonization of the yeast in wounds was observed during the first 3days at 20C, and remained stable after 5-days incubation. On fruits stored at 4C, even after 21days, the population of R.glutinis in wounded fruits was more than 1,600-fold of what it was just prior to storage. In the test on potato dextrose agar plates, agar disks of R.glutinis nutrient yeast dextrose agar cultures placed on PDA plates seeded with pathogens did not inhibit the growth of P.digitatum. Spore germination of pathogens in potato dextrose broth was greatly controlled in the presence of living cell suspensions.

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... Nevertheless, the most common and serious diseases that affect citrus fruit are green and blue moulds caused, respectively, by Penicillium digitatum Sacc. and Penicillium italicum Wehmer, followed in importance by sour rot caused by Geotrichum citri-aurantii Link ex Persn (Caccioni et al. 1998;Palou et al. 2002;Zheng et al. 2005). These pathogens are strict wound pathogens that can infect the fruit in the grove, in the packinghouse, or during subsequent handling and storage . ...
... The nonpathogenic micro-organisms (especially yeasts) protect the surface of citrus fruits by rapid colonization of wounds and thereby exhausting the limited available substrates so that none are available for pathogen to growth. Several yeast species, P. guilliermondii, C. saitoana, R. glutinis, Rhodosporidium paludigenum, K. apiculata, Hanseniaspora guilliermondii and Metschnikowia andauensis, were reported to compete with citrus postharvest pathogens for nutrients and space (Arras et al. 1998;El-Ghaouth et al. 2000;Zheng et al. 2005;Long et al. 2006;Taqarort et al. 2008;Liu et al. 2010) (Table 1). The competition for nutrients and space is favoured by the attachment capability of antagonistic yeasts to pathogen hyphae. ...
... Furthermore, as infection of citrus fruit occurs either prior to harvest or during harvesting and processing, microbial antagonists are expected to display both a protective and curative activity comparable to that observed with synthetic fungicides. However, the biocontrol agents often fail to control previously established infections (Ippolito and Nigro 2000;Zheng et al. 2005). The combination of biological control with other control methods is one of the most promising means of establishing effective integrated disease management strategies. ...
Article
The postharvest diseases of citrus fruit cause considerable losses during storage and transportation. These diseases are managed principally by the application of synthetic fungicides. However, the increasing concern for health hazards and environmental pollution due to chemical use has required the development of alternative strategies for the control of postharvest citrus diseases. Management of postharvest diseases by using microbial antagonists, natural plant-derived products and Generally Recognized As Safe (GRAS) compounds has been demonstrated to be most suitable to replace the synthetic fungicides which are either being banned or recommended for limited use. However, application of these alternatives by themselves may not always provide a commercially acceptable level of control of postharvest citrus diseases comparable to that obtained with synthetic fungicides. To provide more effective disease control, a multifaceted approach based on the combination of different postharvest treatments has been adopted. Actually, despite the distinctive features of these alternative methods, several reasons hinder the commercial use of such treatments. Consequently, research should emphasize the development of appropriate tools to effectively implement these alternative methods to commercial citrus production. This article is protected by copyright. All rights reserved.
... An antagonistic Rhodotorula strain has been reported as an effective biocontrol agent against postharvest decay of apples, pears, sweet cherries, and oranges. Rhodotorula glutinis is an effective biocontrol agent against postharvest fungal spoilage of apples [16] pears [17] oranges [18] sweet cherries [19] as well as strawberries [20]. ...
... The proposed antagonistic mechanism of R. minuta is by competition for space and limited resources as no inhibition zone was observed near to the antagonistic colonies [23]. Biocontrol can also be applied by According to [18], OPA-2, OPA-3, and OPA-9 were the best primers to discriminate yeast strains. The RAPD-PCR technique has been to distinguish between strains or subspecies of microorganisms [27]. ...
... Several antagonistic characteristics are associated with the ability of the yeasts to rapidly reproduce on simple nutrients and to colonise surfaces, while competing for nutrients and space with the other flora [29,30], and the induction of host resistance for some yeasts [31][32][33] and the ability of yeasts to produce cell wall degrading enzymes such as laminarinases, glucanases, proteases, peroxidase and chitinases [33][34][35][36]. Other antagonistic mechanisms can be attributed to the effect of decreasing germ tube length, preventing mycelial growth and suppressing conidial germination [37], the parasitism being associated with the release of hydrolase, the oxidative stress [33] as well as the spoilage fungi and growth inhibition by diffusible volatile organic compounds (VOCs) [38][39][40][41] in synergy with a carbon dioxide enclosed environment [42]. Species of C. pyralidae have previously been studied as producers of killer toxins which can act against beverage spoilage organisms [43]. ...
... Growth inhibition properties of 2-phenylethanol [50,55], ethyl acetate [39] and acetic acid [40] have also been reported. Growth inhibition of spoilage fungi by VOCs have been linked to preventing mycelial growth and suppressing conidial germination [37]. ...
Article
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Undesired fermentation of fruit-derived beverages by fungal, yeast and bacterial spoilage organisms are among the major contributors of product losses in the food industry. As an alternative to chemical preservatives, the use of Candida pyralidae and Pichia kluyveri was assessed for antimicrobial activity against several yeasts (Dekkera bruxellensis, Dekkera anomala, Zygosaccharomyces bailii) and fungi (Botrytis cinerea, Colletotrichum acutatum and Rhizopus stolonifer) associated with spoilage of fruit and fruit-derived beverages. The antagonistic properties of C. pyralidae and P. kluyveri were evaluated on cheap solidified medium (grape pomace extract) as well as on fruits (grapes and apples). Volatile organic compounds (VOCs) from C. pyralidae and P. kluyveri deemed to have antimicrobial activity were identified by gas chromatography-mass spectrometry (GC-MS). A cell suspension of C. pyralidae and P. kluyveri showed growth inhibition activity against all spoilage microorganisms studied. Direct contact and extracellular VOCs were two of the mechanisms of inhibition. Twenty-five VOCs belonging to the categories of alcohols, organic acids and esters were identified as potential sources for the biocontrol activity observed in this study. This study reports, for the first time, the ability of C. pyralidae to inhibit fungal growth and also for P. kluyveri to show growth inhibition activity against spoilage organisms (n = 6) in a single study.
... So far, most studies have examined the antifungal activities of microbial antagonists as a stand-alone product. Results have shown inconsistent performance and control of previously established infections compared to many commercial fungicides (Ippolito and Nigro, 2000;Zheng et al., 2005). Integrated approaches combining biological control with other methods such as salts or food additives, physical treatments, and non-chemical elicitors or plant growth regulators are one of the most promising means of disease management (Huang et al., 1995;Droby et al., 1998;El-Ghaouth et al., 2000;Arras et al., 2002;Janisiewicz and Korsten, 2002;Porat et al., 2002;Zhang et al., 2004;Papoutsis et al., 2019). ...
Article
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Green mold ( Penicillium digitatum ) and blue mold ( Penicillium italicum ) are among the most economically impactful post-harvest diseases of citrus fruit worldwide. Post-harvest citrus diseases are largely controlled with synthetic fungicides such as pyrimethanil, imazalil, fludioxonil, and thiabendazole. Due to their toxic effects, prolonged and excessive application of these fungicides is gradually restricted in favor of safe and more eco-friendly alternatives. This review comprehensively describes alternative methods for the control of P. digitatum and P. italicum : (a) antagonistic micro-organisms, (b) plant extracts and essential oils, (c) biofungicides, (d) chitosan and chitosan-based citrus coatings, (e) heat treatments, (f) ionizing and non-ionizing irradiations, (g) food additives, and (h) synthetic elicitors. Integrating multiple approaches such as the application of biocontrol agents with food additives or heat treatments have overcome some drawbacks to single treatments. In addition, integrating treatment approaches could produce an additive or synergistic effect on controlling both molds for a satisfactory level of disease reduction in post-harvest citrus. Further research is warranted on plant resistance and fruit-pathogen interactions to develop safer strategies for the sustainable control of P. digitatum and P. italicum in citrus.
... Usually, the higher the concentration of an antagonist, the better the biocontrol activity (Zhang et al., 2009). The control of green mould of oranges with yeast Rhodoturula glutinis (Harrison) when applied at a concentration of 1×10 9 cells mL -1 was reported by Zheng et al. (2005). ...
... In the secondary experiment, all tested antagonist gave a significant reduction of green mold, when applied 24 h before pathogen inoculation. However, infection percentages were similar to the untreated control when yeast strains were applied 24 h after pathogen inoculation (data not shown), a finding similar to that of Chalutz and Wilson (1990), Vero et al. (2002) and Zheng et al. (2005). A high level of control was achieved by the yeasts P. anomala strain YT73, D. hansenii strain YT22 and H. guilliermondii strain YT13. ...
Article
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The antagonistic activity of a collection of 245 yeasts strains isolated from the surface of citrus fruits harvested in several orchards of the region Souss-Massa (Agadir, Morocco) has been studied. The assessment of these strains, achieved to basis of their inhibitory effect against Penicillium digitatum Sacc., agent of the green mould, permitted the selection of 21 strains that reduced the rate of rot to less than 50%, among who 7 reduce this rate to less than 20%. The assessment of the protective effect of citrus fruits by the 7 better strains showed a distribution in three categories whose protective rates are respectively 40%, 50 to 60% and 70 to 80%. The identification of these 7 strains permitted to recognize two genera, Candida, with two species, C. famata and C. guilliermondii, and Kloeckera. The study of the population dynamic of these yeasts showed that they actively increase and persist in wounds and on the surface of citrus fruits stored at 25°C during one week.
... Diversos trabalhos relatam a eficácia de R. glutinis no controle de doenças em pós-colheita, como no controle de podridões em frutos de maçãs causadas por Botrytis cinerea e Penicillium expansum (ZHANG et al., 2009a;LI et al., 2011), em combinação com metil jasmonato (MeJA) no controle da podridão cinzenta causada por P. expansum (ZHANG et al., 2009b); no controle da podridão negra pós-colheita em abacaxi causada por 456 Controle pós-colheita... FRANÇA, G. S. et al Ceratocystis paradoxa (REYES et al., 2004); em combinação com ácido salicílico no controle da podridão pós-colheita em morango causado por Rhizopus stolonifer (ZHANG et al., 2010a) e Botrytis cinerea (ZHANG et al., 2007;Zhang et al., 2010b;Ge et al., 2010), no controle de podridões verde ou bolor verde de laranjas causadas por Penicillium digitatum (ZHENG et al., 2005) e integrado com água quente no controle de podridões em pêras causadas por Penicillium expansum e B. cinerea (ZHANG et al., 2008a;ZHANG et al., 2008b) O presente estudo, bem como os inúmeros exemplos citados acima, demonstram a eficácia de R. glutinis no controle de doenças em pós-colheita. Somado a isso, Zhang et al. (2009a) observaram que o tratamento com R. glutinis não afetou os parâmetros de qualidade pós-colheita de maçãs, como perda de massa, firmeza, sólidos solúveis totais (SST), ácido ascórbico (AA), e acidez titulável (AT). ...
Article
Considerando as perdas causadas em pos-colheita pela antracnose no pimentao e a ineficacia das medidas de controle atualmente utilizadas, este trabalho teve por objetivo estudar a potencialidade antagonica in vitro e in vivo de quinze isolados de leveduras a Colletotrichum sp., agente causal da antracnose em pimentao. Foi calculada a porcentagem de inibicao do crescimento do fungo dos tratamentos em relacao a testemunha nos testes in vitro e determinado o tamanho da area lesionada em frutos atraves da mensuracao do comprimento da lesao em dois sentidos diametricamente opostos nos testes in vivo . As leveduras que obtiveram o melhor resultado no controle da antracnose foram identificadas atraves de caracteristicas macroscopicas, microscopicas, fisiologicas, bioquimicas e por taxonomia molecular, sendo os isolados de levedura 13E e 13A1, os que obtiveram as melhores respostas no controle do fitopatogeno tanto in vitro quanto in vivo , identificados como pertencentes a especie Rhodotorula glutinis.
... Mechanisms that have been reported to play a significant role in the biocontrol activity of non-Saccharomyces yeasts against fungi include: competition for nutrients and space (Bencheqroun et al., 2007;Droby et al., 1989;Liu et al., 2013), production of laminarinases and chitinases (Fan et al., 2002;Grevesse et al., 2003;Masih and Paul, 2002), induction of host resistance (Droby et al., 2002;El-Ghauth et al., 2003), reduction in spore germination and decreased germ tube length (Zheng et al., 2005), and inhibition of fungal mycelial growth by diffusible and volatile metabolites (Huang et al., 2011;Lutz et al., 2013). However, there are few reports about antifungal mechanisms of non-Saccharomycesagainst fungi isolated from viticultural environments (Castoria et al., 2001;Rabosto et al., 2006) and there are no reports at all regarding the mechanisms of action of Saccharomyces biofungicides against fungi isolated from grapes. ...
... The result for apples stored at 5 °C for 32 days and 20 °C for 15 days showed that these two strains reduced growth of P. expansum and were effective material for control of pathogen. These strains have also ability for suppressing other pathogen such as green mold of oranges (Penicillium digitatum; Zheng et al. 2004), Grey Mould on Tomato (Botrytis cinerea) (Bello et al. 2008). The adaptation of these two strains to a wide range of temperature provides great market potential for this product for control of postharvest diseases on apples in storage and transportation, as well as under arbitrary temperature in the market places and consumers' home. ...
Article
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In this present research, two yeast antagonists Rhodotorula mucilaginosa (strain A7) and Pichia guilliermomdii (strain A6) isolated from the surface of healthy apples, controlled blue mould of apple caused by Penicillium expansum. This yeast applied instead of fungicide, whatever hazard health and environment. Both antagonists were evaluated as a potential biological control agent for apple blue mould caused by P. expansum. Dual culture, cell free metabolite and volatile test were used in vitro assay. Colony area was recorded compared with controls and percentage of growth inhibition was calculated. Both yeast strains of two genus inhibited growth of P. expansum, the inhibition varied among isolates of two genuses and ranged from 34.51 to 57.62, in dual culture, from 71.86 to 82.6 in volatile metabolite and from 86.03 to 88.77in cell free metabolite test. Both antagonists reduced the incidence of blue mould by 70% at 20 °C. At 5 °C P. guilliermomdii (strain A6) maintained the efficacy of disease control, but R. mucilaginosa (strain A7) only reduced disease incidence by 60%. Moreover P. guilliermomdii (strain A6) exhibited significant protection at lower concentrations than R. mucilaginosa (strain A7). The population of both strains increased in wounds of apples at 20 and 5 °C, and both strains maintained viable over a period of 32 days at 5 °C. Separately, effect of CaCl 2 was mixed yeast was evaluated in 25°C. The different of concentration CaCl 2 reduced decay area from 185.07 to 1738.037 mm 2 compared to 2452.84mm 2 in control after incubation for 15 days.
... The results are presented as the percentage of the control treatment. Isolate PL7T1-S4I3 is R. phylloplana and PL7T2-S6I5 and PLT3-S4I6 are A. pullulans 215 Plum yeasts to be an effective antagonist against brown rot of stone fruits (Mari et al., 2012), and Rhodotorula species were reported to control various fruit decays (Li et al., 2011;Lima et al., 1998;Zhang et al., 2005). ...
Article
Bacterial and yeast antagonists isolated from fruit surfaces have been effective in controlling various post-harvest diseases, and several microbial antagonists have been developed into commercial products. Our knowledge of the fruit microbial community, with the exception of grapes, apples and some citrus fruit, is rudimentary and the potential of the resident yeasts for biocontrol remains largely unknown. We determined the occurrence of yeasts on plum surfaces during fruit development from the pre-hardening stage until harvest for 2 years. A total of 16 species from 13 genera were isolated. Species from three genera, basidiomycetes Rhodotorula (29.5%) and Sporidiobolus (24.7%) and the dimorphic ascomycete genus Aureobasidium (24.7%), constituted 78.7% of all isolations and were recovered throughout fruit development, while Cryptococcus spp. constituted only 6.2% of the total plum isolates. The yeast community in the final sampling was significantly different from the first three samplings, reflecting a rapidly changing fruit habitat during the maturation of fruit. For example, Hanseniaspora, Pichia, Zygosaccharomyces and Wickerhamomyces occurred only on the most mature fruit. Screening of the yeasts for antagonistic activity against Monilinia fructicola, a fungus that causes brown rot, revealed a range of biocontrol activities. Several isolates provided complete control of the decay on plums, challenged with a pathogen suspension of 10(3) conidia/ml and > 90% of control on fruit inoculated with the pathogen at a concentration 10 times higher. Some of the best antagonists included A. pullulans and R. phylloplana. Populations of both of these antagonists increased rapidly by several orders of magnitude in wounds of plums incubated at 24ºC and 4ºC. Our results indicate that plum surfaces harbour several yeast species, with excellent potential for use in biological control of brown rot of stone fruits.
... Cryptococcus laurentii have been studied for postharvest biological control of gray and blue mold rot of apples (Roberts, 1990), peaches (Zhang et al., 2007a), as well as green mold of citrus fruit (Mekbib et al., 2011). Previous studies have indicated that Rhodotorula glutinis and Rhodosporidium paludigenum can significantly inhibit postharvest decay of strawberry (Zhang et al., 2007b) and cherry tomato fruit (Wang et al., 2008), and the two yeast strains have also shown antagonistic activity in reduction of green mold of citrus fruit (Zheng et al., 2005; Lu et al., 2013). However, the effectiveness of single application of biocontrol yeast is much lower than that of the chemical fungicides. ...
... Sacc. and Penicillium italicum Wehmer, followed in importance by sour rot caused by Geotrichum citri-aurantii Link ex Persn (Palou et al., 2002;Zheng et al., 2005). These pathogens are strict wound pathogens that can infect the fruit in the grove, in the packinghouse, or during subsequent handling and storage (Palou et al., 2008). ...
... The use of biological agents in postharvest decay control as alternative to synthetic fungicides has been gathering interest in the last two decades or so, and several studies have demonstrated the potential of certain microbial agents (Wilson and Wisniewski 1989;Zheng et al. 2005;Calvo et al. 2010). Rhodosporidium paludigenum Fell & Tallman, a marine yeast, is highly resistant to osmotic stresses and demonstrated significant reduction of postharvest decays in cherry tomatoes (Wang et al. 2008) and Chinese winter jujube (Wang et al. 2009). ...
Article
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The objective of this study was to analyze the impact of the marine yeast Rhodosporidium paludigenum and sodium bicarbonate (SBC) treatments applied separately or in combination to control green mold of two cultivars of citrus fruit (Citrus reticulata Blanco cv. Subcompressa and C. reticulata Blanco cv. Ponkan) caused by Penicillium digitatum. In the assay of C. reticulata Blanco cv. Subcompressa, R. paludigenum at 107 cells/mL significantly (P < 0.05) reduced green mold incidence compared to the control, and the combination of 107 cells/mL R. paludigenum and 5 % SBC was as effective as fungicide (500 ppm Fungaflor). In the assay of C. reticulata Blanco cv. Ponkan, the treatment with R. paludigenum at 108 cells/mL and 2 % SBC were equally effective and significantly (P < 0.05) reduced the decay incidence. Moreover, the combination of the two treatments completely eliminated the decay incidence, matching the effectiveness of fungicide. This work demonstrated that proper combination of R. paludigenum and SBC can be an alternative to synthetic fungicides for the control of postharvest green mold decay of citrus.
... Our results show minimum inhibitory concentrations (MICs), defined as the lowest concentration of yeasts that resulted in complete growth inhibition of B. cinerea, of 10 6 cfu/mL (S. cerevisiae BSc49, BSc140) and 10 7 cfu/mL (S. cerevisiae BSc5, BSc68, BSc81, BSc92, BSc121, BSc140, BSc175, BSc203) in wounded grapes and at 25 • C (Table 3). These concentrations are lower than those found for other biocontrol yeasts (Zhang et al., 2007;Tian et al., 2002;Chanchaichaovivat et al., 2007;Zheng et al., 2005). An increase in the concentrations of some yeasts significantly improved their biocontrol activity with higher R 2 values (Table 3). ...
Article
Botrytis cinerea, the causal agent of gray mold, is an important disease of grapes. Yeasts are members of the epiphytic microbial community on surfaces of fruits and vegetables and because some yeasts inhibit fungi they are used as biocontrol agents. The major objective of the present work was to isolate yeasts from grapes, vineyard soil, and grape must and select them for their ability to prevent gray mold onset after harvest. Yeasts that were found effective against the fungus were also assayed for their possible pathogenicity in humans. Two antagonism experiments were performed to study the effect of yeasts on B. cinerea, an in vitro study with Czapeck Yeast Extract Agar and an in vivo study with grape berries at 2 °C and 25 °C; both experiments were conducted at different yeast concentrations (105, 106 and 107 cfu/mL). Antagonists were subsequently assayed for their ability to colonize and grow in fruit wounds. The biocontrol yeasts were also examined for their possible pathogenicity in humans: phospholipase and proteolytic activity, growth at 37 °C and 42 °C, pseudohyphal formation and invasive growth. A total of 225 yeasts belonging to 41 species were isolated from must and grape berries and 65 of them, representing 15 species, exhibited in vitro inhibition of B. cinerea at 25 °C. These 65 biocontrol yeasts were subsequently assayed in vivo and 16 of them (15 Saccharomyces cerevisiae and 1 Schizosaccharomyces pombe) showed antagonistic properties against B. cinerea at 25 °C. Only one isolate (S. cerevisiae BSc68) was able to inhibit mycelial growth of B. cinerea on grape berries at both 2 °C and 25 °C. The biomass of this strain in grape wounds increased 221.5-fold at 25 °C after 3 d and 325.5-fold at 2 °C after 10 d of incubation. An increase in the concentration of certain yeasts significantly enhanced their antagonistic activity. All yeast isolates determined as biocontrol agents under in vivo conditions were isolated from fermenting musts. Twelve biocontrol agents (S. cerevisiae) revealed one or more phenotypical characteristics associated with pathogenicity in humans but none of them showed all characteristics together. The fact that there exist few reports on S. cerevisiae and none on Sch. pombe as biocontrol agents against B. cinerea makes our results even more relevant.
... Zhang, Zheng, and Xi (2005) reported a reduction in disease caused by P. italicum with higher levels of Cryptococcus laurentii on sweet oranges. Zheng, Zhang, and Sun (2005) found lower incidence of P. digitatum in oranges with increasing doses of Rhodotorula glutinis and Liu et al. (2010) found that higher levels of C. laurentii and Rhodosporidium paludigenum inoculum reduced infection by Geotrichum citri-aurantii on mandarin (C. reticulata). ...
Article
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The effect of administration of the concentration of five strains of Debaryomyces hansenii on protecting the Mexican lime from Penicillium italicum was measured. Imazalil fungicide was applied as a control treatment for comparison. The most effective treatments for reducing the severity of P. italicum on fruit at room temperature were intermediate (1 × 10 cells mL) and high (1 × 10 cells mL) doses of antagonistic yeasts. Cold-stored fruits were protected better by the highest dose of yeast. The protection of antagonistic yeasts in both temperatures was similar to imazalil.
... Previous studies indicated that yeast populations such as Rhodotorula glutinis (Fresen.) F.C. on orange increased by approximately 10,000-fold during the first 3 days at 20°C and 40,000-fold after 7 days 4°C (Zheng et al., 2005). A marked increase of M. pulcherrima and Hanseniaspora uvarum (Niehaus) populations was also observed on apples (Piano et al., 1997) and grapes (Liu et al., 2010) respectively. ...
Article
The antagonistic effects of yeasts, L1 and L8, isolated from carposphere of ‘Redhaven’ peaches were tested for the first time in the same experiment against three Monilinia species (Monilinia laxa, Monilinia fructicola and Monilinia fructigena) in in vitro and in vivo trials. The two antagonists were selected after preliminary assays for their ability to reduce brown rot in peaches and nectarines, and both were identified by molecular and morphological tools as Aureobasidium pullulans. In in vivo trials, neither the autoclaved cells, nor the sterile culture filtrates of either antagonist showed any significant reduction of rot incidence produced by inocula of the three Monilinia species, while the washed cells of L1 and L8 completely inhibited M. laxa and M.fructicola rots and reduced M. fructigena infections by 70% and 90%, respectively. In other trials, nectarines treated with antagonist cells and inoculated with the pathogens were stored at 0°C for 21days, plus 7days at 20°C. The low temperature reduced brown rot development, since all fruit were free from disease symptoms on removal from cold storage. However after 7d at 20°C, untreated fruit were rotted over 45% depending on the Monilinia species but the antagonists completely inhibited M. laxa and M. fructicola, while M. fructigena infections were reduced by 89.8% and 91.2% by L1 and L8, respectively. For both strains, 108CFUml−1 was the most active concentration, although L1 showed good activity at a concentration of 107CFUml−1. Isolate L8 at the concentration of 107CFUml−1 was ineffective against M. fructicola and M. fructigena, showing no difference between treated fruit and the control, excepting the case of nectarines inoculated with M. laxa, where L8 at the concentration of 107CFUml−1 reduced the brown rot infections with respect to the control. The increase in population density of A. pullulans strains L1 and L8 in the wounds of nectarines stored at 0° or 20°C was low but sufficient to control brown rot. In conclusion, the present preliminary study identified two antagonistic strains of A. pullulans as active ingredients for the development of biofungicides for postharvest application against three Monilinia species that are responsible for high economic losses in stone fruit crops.
... Chanchaichaovivat et al. (2007) were able to control anthracnose on chilli (6.5% disease incidence) caused by Colletotrichum capsici, with a yeast Pichia guilliermondii Strain R13, applied at 10 8 cells ml À1 . Zheng et al. (2005) were also able to control green mold of oranges with yeast Rhodotorula glutinis (Harrison), applied at a concentration of 1 Â 10 9 cells ml À1 . Reports by Janisiewicz (1988) and Hong et al. (1998) demonstrated that a direct relationship exists between the population density of the biocontrol agents and the effectiveness of the postharvest biological control treatment. ...
Article
A total of 60 yeast and 92 Bacillus isolates were isolated from the fruit surface of papaya and several varieties of citrus from various orchards in South Africa, and screened for antagonism to Penicillium digitatum. Ten yeast and 10 Bacillus isolates reduced the surface area of visible P. digitatum growth ⩾50%, when applied 3h before inoculation with the pathogen. Two yeast isolates (B13 and Grape), when applied 48h prior to inoculation with P. digitatum, prevented decay of navel oranges and lemons, and ⩽5% incidence on Valencia oranges, compared with an untreated control that had ⩾50% incidence of infection. The application of isolates to lemons and Valencia oranges did not produce a curative action against P. digitatum when applied 3h postinfection. The yeast isolates B13 and Grape were superior to all the Bacillus isolates, and provided excellent control of P. digitatum, when applied to citrus fruit prior to artificial inoculation by P. digitatum.
... Furthermore, in another studies (in vitro) an antagonistic yeast strain of Rhodotorula glutinis has been reported as an effective biocontrol agent against post-harvest decay of apples (Qin et al., 2003), pears (Zhang et al., 2008;Zhang et al., 2009), strawberries (Zhang et al., 2007), sweet cherries (Tian et al., 2004) and oranges (Zhang et al., 2005). Also, an antagonistic yeast strain of Rhodotorula glutinis and its autoploidy have been reported as an effective biocontrol agent (in vitro) and (in vitro) against grey mould of greenhouse sweet pepper (Haggag, et al., 2005). ...
... During the last 25 years, several research programs have been developed around the world and numerous biological control agents have been investigated against different postharvest diseases of fruit (Nunes et al., 2009). As a result, some microorganisms have been reported and patented as postharvest biocontrol agents (Janisiewicz and Roitman, 1988;Chalutz and Wilson, 1990;McLaughlin et al., 1992;Janisiewicz and Jeffers, 1997;Droby et al., 1998;Viñas et al., 1998;Fan et al., 2000;Janisiewicz et al., 2001;Kurtzman and Droby, 2001;Nunes et al., 2001;Adikaram et al., 2002;Zheng et al., 2005;Govender and Korsten, 2006). Despite this, only a few commercial products are available, such as Biosave TM (Pseudomonas syringae, Jet harvest solutions, USA), Shemer TM (Metschnikowia fructicola, Bayer Crop Science, AG), Candifruit TM (Candida sake CPA-1, Spicam-Inagra, Spain), Pantovital TM (Pantoea agglomerans, Biodurcal S.L., Spain), Serenade TM (Bacillus subtilis, AgraQuest, USA) and Boniprotect TM (Aureobasidium Pullulans, Bioprotect, Germany). ...
Article
Potential antagonists were isolated from the epiphytic flora associated with oranges and pome fruit. A total of 1465 microorganisms were tested in a preliminary screening against blue and green moulds on pome and citrus fruit, respectively. Among them, approximately 3% reduced incidence and severity by more than 50% and 4 microorganisms fulfilled the selection criteria of reduction in severity and incidence by 75%. The most effective was a yeast identified as Metschnikowia andauensis, strain NCYC 3728 (PBC-2), isolated from the surface of ‘Bravo de Esmolfe’ apple fruit cultivated in North Portugal. The biocontrol activity of M. andauensis PBC-2 was dependent on its applied concentration. At 5×106cfu/mL incidence (% of infected wounds) and severity (lesion diameter) were reduced by 62 and 70%, respectively and at 1×107cfu/mL, the greatest reduction was achieved, 90% of incidence and 95% of severity. The broad spectrum of action of M. andauensis PBC-2 was evaluated with effective control being achieved against Rhizopus stolonifer, Penicillium expansum and Botritys cinerea, on ‘Rocha’ pears and on different apple cultivars and against Penicillium digitatum and Penicillium italicum on mandarins and oranges. In semi-commercial trials in cold storage, the reduction of blue mould was 90%. Rapid colonization of fresh apple fruit wounds was observed during the first 24h of cold storage, followed by a significant population increase during the first 15days of storage and then the population remained stable until the end of storage.
... In the secondary experiment, all tested antagonist gave a significant reduction of green mold, when applied 24 h before pathogen inoculation. However, infection percentages were similar to the untreated control when yeast strains were applied 24 h after pathogen inoculation (data not shown), a finding similar to that of Chalutz and Wilson (1990), Vero et al. (2002) and Zheng et al. (2005. A high level of control was achieved by the yeasts P. anomala strain YT73, D. hansenii strain YT22 and H. guilliermondii strain YT13. ...
... In this review, this category will be restricted to the utilisation of microbial antagonists. Substantial progress has been made in developing antagonistic microorganisms for the control of postharvest diseases [ [190*, 191], Metschnikowia mulcherrima [192*], Rhodotorula glutinis [193], Cryptococcus laurentii [194*], Kloeckera apiculata [195, 196*], Pichia anomala [197]), bacteria (eg, Pseudomonas syringae [198**-201], Pseudomonas cepacia [202][203][204] In spite of the large volume of research published about postharvest biocontrol of citrus rots, the commercial use of these products was and remains limited and accounts for only a very small fraction of the potential market. As discussed in several reviews [173, 174, 176*, 177**, 232], the main shortcoming of the use of postharvest biocontrol products has been inconsistency in their performance, especially when used as a stand-alone product to replace synthetic fungicides. ...
Article
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Purpose of review: This article reviews research based on the evaluation of postharvest control methods alternative to conventional chemical fungicides for the control of citrus green and blue moulds, caused by the pathogens Penicillium digitatum and P. italicum, respectively. Emphasis is given to advances developed during the last few years. Potential benefits, disadvantages and commercial feasibility of the application of these methods are discussed.Findings: Substantial progress has been accomplished in selecting and characterising new effective physical, chemical and biological control methods. However, their widespread commercial implementation relies, in general, on the integration of different treatments of the same or different nature in a multifaceted approach. For satisfactory penicillium decay control, this postharvest approach should be part of an integrated disease management (IDM) programme in which preharvest and harvest factors are also considered.Limitations: The lack of either curative or preventive activity, low persistence, high variability, inconsistency or excessive specificity are general limitations associated with the use of alternatives to synthetic fungicides as stand-alone treatments. Furthermore, the risk of adverse effects on fruit quality, technological problems for cost-effective application, or the availability of new conventional fungicides for traditional markets are additional reasons that may hinder the broad commercial use of such treatments.Directions for future research: As we learn more about the fundamental basis underlying host-pathogen interactions and how they are influenced by direct or indirect protective effects of existing or new single alternative treatments, more effective methods of applying and combining complementary approaches for additive or synergistic effects will emerge. Research should provide appropriate tools to tailor the application of these nonpolluting postharvest control systems and, further, the complete IDM strategy for each specific situation (ie, citrus species and cultivar, climatic and seasonal conditions, destination market, etc).
... The inhibition of spore germination of pathogenic moulds plays an important role in biological control by yeasts. Multiple studies have shown that the concentration of antagonistic yeasts is a determinant of the inhibition of spore germination (Zheng et al., 2005). In this assay, both antagonistic yeast strains totally inhibited the conidial germination of P. expansum M639 when were inoculated at 5 Â 10 8 cells/mL on PDB. ...
Article
Fresh fruit is highly perishable during postharvest life, mainly due to fungal growth. Thus, fungal control is an important goal for the fruit industry. In this work, a selection of antagonistic yeasts isolated from fig and breba crops were screened in vitro. The isolated yeasts were challenged with three moulds isolated from decayed figs and breba crops, identified as Penicillium expansum M639 and Cladosporium cladosporioides M310 and M624, and pathogenic moulds Botrytis cinerea CECT20518 and Monilia laxa CA1 from culture collections. Two yeast isolates, Hanseniaspora opuntiae L479 and Metschnikowia pulcherrima L672, were selected for their ability to inhibit the growth of aforementioned moulds. These yeasts reduced the radial growth of moulds on PDA by between 45.23% and 66.09%. Antagonistic activity was associated with the interaction of live yeast cells with moulds. M. pulcherrima L672 apparently parasitised C. cladosporioides isolates. In addition, challenges were assayed using wounded apples and nectarines, with significant reductions in percent infection and lesion size for all moulds tested. To our knowledge, this is the first report identifying H. opuntiae as an antagonist against different pathogenic moulds.
... Spore suspensions of the pathogen were obtained from the isolate grown on PDA at 25 • C for 14 d. Spore concentrations were determined by a hemocytometer and adjusted with sterile distilled water ( Zheng et al., 2005). ...
Article
A bacterial strain SG-6, isolated as an endophyte from the root tissue of Sophora tonkinensis, was identified as Paenibacillus polymyxa based on morphology, 16S rDNA gene analysis and Biolog tests. The strain was found to be highly effective in reducing postharvest green mold decay of citrus fruit caused by Penicillium digitatum. In an in vitro assay by dual-culture of strain SG-6 and P. digitatum on potato dextrose agar plates, the bacterium significantly inhibited growth of P. digitatum. Conidial germination of the pathogen was greatly inhibited in the presence of the living bacterial cell suspensions. In tests of in vivo activity, the unwashed cell suspension of strain SG-6 was more effective than the washed cell suspension and culture filtrate. Green mold control improved when the period between treatment with strain SG-6 and inoculation with the pathogen was increased. The concentration of the antagonist also had a significant effect on biocontrol effectiveness. At the concentration of 1 x 10(9) cells mL(-1) of strain SG-6, the disease incidence and lesion diameter declined to 18.3% and 5.5 mm, respectively, which were significantly lower than control after 5 d of incubation at 25 degrees C. Population of strain SG-6 increased rapidly in citrus fruit wounds when inoculated at 25 degrees C but remained static at 6 degrees C. The bacterium also significantly reduced the natural development of green mold decay of citrus fruit following storage at 25 degrees C for 4 weeks or at 6 degrees C for 4 weeks followed by 25 degrees C for 2 weeks. Furthermore, it did not impair the quality parameters, including weight loss, firmness, total soluble solids, ascorbic acid, and titratable acidity. To our knowledge, this is the first report about antagonistic P. polymyxa strain SG-6 as a promising biocontrol agent against postharvest green mold of citrus fruit.
... It needs to be noted that despite the ability of this yeast to inhibit the growth of A. carbonarius, it could not totally inhibit fungal sporulation (Fig. 2). Spore production, which is related to toxin production (Calvo et al., 2002), is inhibited by the presence of antagonistic yeasts and previous researchers have reported that yeasts could be employed as biocontrol agents of fungal sporulation (Ruiz-Moyano et al., 2016;Zheng et al., 2005). The growth area rate of the fungi was influenced by the presence of yeasts (Table 2). ...
Article
The aim of the present study was to investigate the interaction between 67 different yeast isolates and 3 wild isolates of Aspergillus carbonarius originated from Greek vineyards and characterized by high ochratoxigenic potential. The selected fungi were used either as single cultures or combined in a mixed culture. Yeasts and fungi were grown as mono-cultures and co-cultures in solid (MEA, CYA) and liquid (CY broth) media, grape berries and sterilized grape juice. Fungal growth was monitored by means of colony area measurements. The model of Baranyi and Roberts was further fitted to growth data to provide estimates of the colony area growth rate (cm2/day). Moreover, OTA analysis was undertaken for CY broth and agar as well as for grape berries and juice, on the 8th and 15th days of incubation at 25 °C. A significant reduction in fungal growth rate, final colony size and toxin production was observed in both liquid and solid media by the different yeast species assayed. The most competitive strains belonged to Saccharomyces, Pichia, Metschnikowia, Dekkera and Rhodotorula genera. Similar results were obtained from inoculated grape berries and grape juice. Specifically, Saccharomyces cerevisiae Y33 resulted in a decrease in fungal colony area of >90% and 93% after 3 and 4 days of co-culture, respectively. Similar results were obtained for OTA, where toxin concentration of the highest producer (A. carbonarius F3) was reduced from 14,983 and 31,565 ng/mL at 8 and 15 days, respectively, to 5 ng/mL and below detection limit (1 ng/g) when co-cultured with S. cerevisiae Y33. The results of this study could provide a pool of yeast species that must be further investigated for potential application as biological control agents at pre- and post-harvest level in wine and grape juice processing.
... This will lead to new, innovative approaches for controlling of decay due to postharvest disease (Droby, 2006). Biocontrol of postharvest diseases of different fruits using antagonistic microorganisms isolated from plant tissues has been successfully achieved (Janisiewicz and Korsten, 2002; Zheng et al., 2005; Zheng et al., 2007). Some antagonists were successfully applied in biocontrol of postharvest diseases of cherry tomato fruit (Schena et al., 1999; Wang et al., 2008). ...
Article
Full-text available
Rot of cherry tomato (Lycopersicon esculentum) fruits caused by several fungal pathogens is a detrimental disease leading to substantial yield loses worldwide. Alternaria isolates were the most common fungal species isolated from healthy or rotten fruits. Trichoderma harzianum spore suspension and culture filtrate were tested for their antagonistic activity on controlling tomato fruit rot. T. harzianum isolates suppressed or interfered with the growth of different postharvest tomato fungal pathogens albeit at different degrees. Their culture filtrate inhibited pathogen spore germination possibly due to the released extracellular diffusible metabolite(s). Besides, aberrant morphology of conidia was observed with deformation of hyphal tips. Furthermore, the resulting mycelia appeared desiccated with coagulated protoplasm leading to complete collapse of protoplasm in presence of T. harzianum culture filtrate. Application of T. harzianum spores to tomato fruits decreased disease severity significantly with the most profound effect at higher spore concentrations (108 cells per ml). Similarly, culture filtrate of T. harzianum prevented pathogen spore germination on the surface of tomato fruits leading to decreased incidence of rot symptoms at high culture filtrate concentrations. This work provides strong evidence that T. harzianum is a competent antagonist and its spore suspension and culture filtrate can be used efficiently to control postharvest tomato rot.
... The typical strategy for biocontrol is to use living organisms to suppress or inhibit the growth, infection, or reproduction of another organism [39]. Disease control by exploiting antagonist organisms has become a viable disease management strategy, and several microorganisms have been successfully patented as postharvest biocontrol agents [40][41][42][43]. According to Alvinda and Natsuaki [44], the most viable way of using antagonist microorganisms as biocontrol agents is by supporting and maintaining existing antagonists which already reside and are established on the target plant environments. ...
Article
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Colletotrichum gloeosporioides causes anthracnose disease in papaya fruit resulting in tremendous economic loss due to its latent infection. This study aimed to evaluate the biocontrol activity of antagonistic yeasts against C. gloeosporioides in papaya and determine the possible mechanism involved. One hundred and ten yeast strains were isolated from different parts of the papaya plant. Among them, only five strains, namely F001, F006, L003, FL013 and LP010, showed more than 55% radial growth inhibition of C. gloeosporioides. These five potent yeast strains were further evaluated in vitro and in vivo. The results indicated that strain F001 had the strongest biocontrol activity based on spore germination and fungal growth inhibition. In vivo, the strain F001 caused 66.7% and 25% reductions in disease incidence and severity, respectively. Based on molecular identification, the strain F001 was confirmed as Trichosporon asahii. Despite there was no significant induction of defense enzyme activities found on the treated fruits, SEM observation showed direct attachment of T. asahii with the fungal hyphae and interfere in their establishment to the fruit surface. Based on these findings, the antagonistic yeast T. asahii strain F001 may be used as a potential natural biological control agent against anthracnose disease in papaya fruit.
... Although new chemical agents [19][20][21] and peptides [22] for the control of P. digitatum are being developed, biological control remains the most promising option [8]. Among biocontrol agents, antagonistic yeasts have been the most frequently tested organisms [3,8,10,[23][24][25][26][27][28][29]. Recent work highlighted the use of the killer yeast Clavispora lusitaniae strain 146 as a promising biocontrol agent against P. digitatum. ...
Article
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Fungal rots are one of the main causes of large economic losses and deterioration in the quality and nutrient composition of fruits during the postharvest stage. The yeast Clavispora lusitaniae 146 has previously been shown to efficiently protect lemons from green mold caused by Penicillium digitatum. In this work, the effect of yeast concentration and exposure time on biocontrol efficiency was assessed; the protection of various citrus fruits against P. digitatum by C. lusitaniae 146 was evaluated; the ability of strain 146 to degrade mycotoxin patulin was tested; and the effect of the treatment on the sensory properties of fruits was determined. An efficient protection of lemons was achieved after minimum exposure to a relatively low yeast cell concentration. Apart from lemons, the yeast prevented green mold in grapefruits, mandarins, oranges, and tangerines, implying that it can be used as a broad-range biocontrol agent in citrus. The ability to degrade patulin indicated that strain 146 may be suitable for the control of further Penicillium species. Yeast treatment did not alter the sensory perception of the aroma of fruits. These results corroborate the potential of C. lusitaniae 146 for the control of postharvest diseases of citrus fruits and indicate its suitability for industrial-scale fruit processing.
... Some fungal species cause postharvest infections in citrus fruit, resulting in important economic losses (Moss 2008). The most important pathogenic fungi causing postharvest infections include Penicillium digitatum and P. italicum (Ascomycota; Eurotiomycetes; Eurotiales), responsible for green and blue rot, respectively, and Geotrichum candidum (Ascomycota; Saccharomycetes; Saccharomycetales), responsible for sour rot (Zheng et al. 2005;Valero & Serrano 2010). ...
Article
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This study aimed to evaluate the antifungal activity of oregano and clove essential oils and their main components (thymol, carvacrol and eugenol) against Penicillium digitatum, as well as against isolates of Penicillium italicum and Geotrichum candidum resistant to imazalil or guazatine, respectively. In vitro tests were conducted by a direct contact method on potato dextrose agar medium. The results indicated that the essential oils and their main components were effective in inhibiting fungal growth, with thymol displaying the highest efficacy. The antifungal activity of thymol was evaluated further on orange fruit infected experimentally with a suspension of spores of P. digitatum, G. candidum or a mixture of both fungi, using isolates resistant to chemical fungicides. Treatment of the oranges with the thymol solutions reduced or totally inhibited the development of fruit decay, depending on the thymol concentration used. These essential oils and their main components demonstrated a strong antifungal effect against Penicillium spp. and G. candidum resistant to chemical fungicides. They may have potential as active compounds for the formulation of natural preparations to use as alternatives to synthetic fungicides for the management of green, blue and sour rot in citrus fruit.
... For example, a recent taxonomic reclassification based on a number of morphological traits combined with molecular analyses was performed for Pucciniomycotina yeasts ). The family Sporidiobolaceae, which originally included the genera Rhodotorula, Rhodosporidium, Sporobolomyces, and Sporidiobolus, is of interest in this work because it includes several red yeasts that are reported to be BCAs of plant pathogenic fungi (Castoria et al. 2003(Castoria et al. , 2005Cheng et al. 2016;Ianiri et al. 2013;Pinedo et al. 2018;Yan et al. 2014;Zhang et al. 2007;Zheng et al. 2005Zheng et al. , 2017. Reclassification placed Rhodosporidium and Sporidiobolus in the novel genus Rhodosporidiobolus, with consequent name changes in several species. ...
Article
The field of plant protection is steadily reducing the use of chemicals by increasing the use of microbial biocontrol agents. At present, several microorganisms are active ingredients of the so-called biofungicides and some of these are based on yeasts. Molecular techniques applied in microbial taxonomy are leading to extensive revisions of the classification of many microbial groups, including various yeasts used for biocontrol. Recent taxonomic revision of the basidiomycete genus Cryptococcus resulted in C. laurentii (Kufferath) Skinner (Tremellales) being renamed as Papiliotrema laurentii, including strains displaying biocontrol activity, such as strain LS28. In this study, we performed comparisons of ITS, D1D2, TEF1, and RPB1 nucleotide sequences of LS28 with the corresponding genes of the type strains of taxonomically related species. We found that the yeast strain LS28 belongs to the species P. terrestris (Tremellales) (Crestani et al. Int J Syst Evol Microbiol 59:631–636, 2009) rather than P. laurentii. We encourage other groups working on biocontrol to perform molecular characterization of their yeast(s) of interest to identify the species that have the highest potential for practical applications and facilitate possible commercial registration.
... Several studies investigated using yeasts in biocontrol management to reduce or replace synthetic fungicides (Droby et al. 2009;Liu et al. 2013). In general, mechanisms of yeasts against fungi can be summarized as a competition for space and nutrients (Bencheqroun et al. 2007;Liu et al. 2013), induce host resistance (Droby et al. 2002;El-Ghauth et al. 2003), produce volatile compounds that can inhibit fungal growth (Huang et al. 2011;Lutz et al. 2013), produce chitinases and hydrolytic enzymes (Fan et al. 2002;Grevesse et al. 2003;Masih and Paul 2002), and reduce spore germination (Zheng et al. 2005). El-Fiki (2017) mentioned that commercial dry yeast (consortia of S. cerevisiae) significantly reduced chocolate leaf spot disease in broad bean with 75% concentration at 8 days postinoculation when compared with control. ...
Article
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This study was conducted to determine the effect of adding yeast to compost tea in the biocontrol activity of compost tea against chocolate leaf spot disease in broad bean as a proposed biocontrol treatment, in addition to effects on soil biota, yield, and growth parameters of broad bean. Faba bean was planted in plastic bags filled with 11 kg of non-sterilized clay soil. Foliar compost tea–yeast mixture was applied 40 days post-sowing and 1 day pre-inoculation with Botrytis fabae spore suspension. Soil drenching was done directly, before seeds sowing, at a rate of 100 ml/bag. Seed treatment was done for 24 h before seeding. The trial was designed in complete randomized block design with three triplicates for each treatment. Adding yeast to compost tea as seed soaking treatment significantly decreased the disease severity when integrated with foliar spray and soil drenching. Foliar and seed soaking treatments significantly increased pod number, seed weight, and population of soil microorganisms. Foliar treatment increased peroxidase enzyme content. Seed soaking treatment increased polyphenol oxidase enzyme level. Total phenol content increased with foliar spray, seed soaking, and soil drenching when compared with control. It can be concluded that adding of the yeast to compost tea in seed soaking treatment resulted into biocontrol of chocolate leaf spot disease of broad bean, increased soil microorganism population, pod number, seed weight, polyphenol oxidase enzyme, and total phenolic contents.
... Actually, some biocontrol strains perform well under controlled conditions in the laboratory, where normally the fruit used have the same level of maturity, but may not do the same under controlled atmosphere cold storage in the packinghouses , where it is not possible to control the physiological conditions of the fruit tested. Zheng et al. (2005) reported that the efficacy of the biocontrol strains at room temperature and under cold storage conditions was determined by the nutritional environment at the wound site which may or may not favour the growth and colonization. The only postharvest fungicide admitted in Italy and in many other countries is benzimidazole thiabendazole, whose efficacy is poor due to the development of resistant populations of P. expansum and B. cinerea (Baraldi et al., 2003; Bertetti et al., 2003). ...
... Rhodosporidium toruloides is a strong candidate for bioconversion of pectin-rich waste streams. This basidiomycetous red yeast has been isolated from a wide variety of pectin-rich substrates (e.g., oranges [13], grapes, olives [14], and sugar beet pulp [14,15]). R. toruloides can grow well on D-galUA as a sole carbon source (16), indicating an efficient pathway for D-galUA metabolism. ...
Article
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The switch from the traditional fossil-based industry to a green and sustainable bioeconomy demands the complete utilization of renewable feedstocks. Many currently used bioconversion hosts are unable to utilize major components of plant biomass, warranting the identification of microorganisms with broader catabolic capacity and characterization of their unique biochemical pathways. d -Galacturonic acid is a plant component of bioconversion interest and is the major backbone sugar of pectin, a plant cell wall polysaccharide abundant in soft and young plant tissues. The red basidiomycete and oleaginous yeast Rhodosporidium toruloides has been previously shown to utilize a range of sugars and aromatic molecules. Using state-of-the-art functional genomic methods and physiological and biochemical assays, we elucidated the molecular basis underlying the efficient metabolism of d -galacturonic acid. This study identified an efficient pathway for uronic acid conversion to guide future engineering efforts and represents the first detailed metabolic analysis of pectin metabolism in a basidiomycete fungus.
Article
Abstract The value of healthy forest ecosystems is well known and trees in these systems form symbioses with a variety of living organisms. This review focuses on literature pertaining to the potential interactions of arboreal yeast endophytes with trees and their associated insects. Although very little is known about the symbioses of arboreal yeast endophytes, indications are that some of these unicellular fungi produce plant-growth promoting phytohormones, while others are antagonistic towards phytopathogens or are capable of producing pheromones that affect the behavior of insect herbivores. However, more research needs to be conducted to fully understand the role of arboreal yeast endophytes in ecosystem processes.
Chapter
The multitasked Nitric oxide (NO) is a highly reactive, gaseous molecule that is endogenously produced in the plant cells through various routes. In the plant, NO participates in numerous physiological processes including growth and development as well as adaptation against (a)biotic stresses. At the molecular level, NO acts as a redox-related signaling molecule whose function entirely depends on two factors (concentration and spatial generation pattern). Once generated, it directly or indirectly interacts with other redox-related molecules (O2−, H2O2, H2S, NO2−) and potentially interacts with various biomolecules including proteins, lipids, hormones, and nucleic acid at the downstream level. The variety of NO acting mechanisms include direct reaction with redox molecule, metal-nitrosation of transient metals, protein tyrosine nitration, and S-nitrosation. Since the discovery of the physiological role of NO in plants, numerous studies have been conducted to elucidate the production pathways, mechanism of action, and its ultimate effect in distinct physiological processes. However, over time, some questions still remain unanswered, and with new knowledge on interactions of NO with fatty acids and nucleic acids, more possible regulatory roles of NO in mitigation of stresses is still under investigation. Therefore, this chapter discusses the NO production, mechanism of action, and role in the regulation of plant’s (a)biotic stress response.
Article
Fungal pathogens are the main biotic burden of productivity for economically important crops under field, greenhouse or postharvest conditions. The discovery and development of new environmental-friendly solutions, such as application of living organisms and their derivatives to control plant diseases and pests, are of enormous interest. This study presents the results of a mass screening designed to detect yeast strains with antagonistic activity against postharvest pathogens (Alternaria alternata, Penicillium expansum and Botrytis cinerea) and soil-borne diseases (Verticillium dahliae and Fusarium oxysporum). In fact, this is the first study that focuses on screening the antagonistic potential of a wide variety of yeast genera (13) and species (30) against vascular wilts. The results from in vivo trials demonstrated that fungal infected tomato plants, grown under hydroponic or soil conditions, showed a significant reduction in disease severity after yeast treatment. Wickerhamomyces anomalus Wa-32 was able to antagonise both pathogens and reduce the disease severity up to 40% (V. dahliae) and 60% (F. oxysporum) in soil conditions. In addition, this strain became endophytic in tomato plants. The features of Wa-32 are of enormous interest since no effective antagonistic biocontrol product is available for the simultaneous control of these two fungal pathogens. Postharvest assays with wounded tomato fruits showed that several strains displayed very high biocontrol levels against P. expansum and B. cinerea (up to 86 and 97% reduction in disease severity, respectively) but none of them showed protection against A. alternata. The best protection against B. cinerea was again achieved with W. anomalus Wa-32 and two Metschnikowia pulcherrima strains (Mp-22 and Mp-30). However, the best antagonistic strains of P. expansum were Candida lusitaniae Cl-28, Candida oleophila Co-13, Debaryomyces hansenii Dh-67 and Hypopichia pseudoburtonii Hp-54. These biocontrol effects were also demonstrated in grapes and apples.
Article
The effect of biocontrol yeasts and pyrimethanil at low concentration on inhibition of blue mold rot caused by Penicillium expansum in pear fruit was investigated. Pyrimethanil at low concentration (40μg/mL) alone had little inhibitory activity against the P. expansum infection in pear fruit wounds although it was effective in inhibiting the survival of P. expansum on Asp-agar medium. Pyrimethanil at this low concentration significantly enhanced the efficacy of Cryptococcus laurentii at 1×10(7)CFU/mL in reducing blue mold rot in vivo compared with C. laurentii at 1×10(7)CFU/mL alone. However, there was no additive inhibitory activity when pyrimethanil was combined for application with biocontrol yeasts Rhodosporidium paludigenum or Rhodotorula glutinis. Combination of pyrimethanil and C. laurentii at low concentration also inhibited blue mold rot when P. expansum was inoculated into fruit wounds 12h before treatment and fruit was stored at low temperature (4°C). Pyrimethanil at 0.04 to 400μg/mL did not influence the survival of C. laurentii in vitro, and it only slightly reduced the population growth of C. laurentii after 48h of incubation in the pear fruit wounds. There was no significant difference in quality parameters including total soluble solids, titratable acidity and ascorbic acid of pear fruit wounds among all treatments after 5days of treatment at 25°C. Integration of C. laurentii and pyrimethanil at low concentration might be an effective and safe strategy to control P. expansum infection in pear fruit, especially in an integrated postharvest disease management strategy.
Article
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Yeasts are distributed in all environments and have been reported as potential biocontrol agents against various phytopathogenic fungi. To investigate their enzymatic and biological activities, 32 yeasts were isolated from 15 date vinegar samples. Evaluation of the antagonistic activities of isolated yeasts against the plant pathogens Fusarium oxysporium, Sclerotinia sclerotiorum, and Macrophomina phaseolina indicated that there are two yeasts had the highest inhibitory effect against plant pathogens, these yeasts identified as Kluyveromyces marxianus and Torulaspora delbrueckii using traditional and molecular methods. These yeast isolates were tested for fungal cell wall degrading enzymes (in vitro), and results indicated that the yeasts had strong protease and amylase enzyme activity and moderate chitinase and cellulase enzyme activity. The antagonistic activities of each yeast were evaluated using a dual culture technique. The results showed that K. marxianus inhibited the mycelial growth of F. oxysporium, S. sclerotiorum, and M. phaseolina by 70.5, 57.5, and 75.5%, respectively, whereas T. delbrueckii inhibited mycelial growth of F. oxysporum, S. sclerotiorum, and M. phaseolina by 55.3%, 66.2%, and 31.11%, respectively. The biofilm production assay indicated that the tested yeast could form biofilms as a mechanism of antagonistic activity against phytopathogenic fungi.
Article
Post-harvest commodities wastage due to decay caused by the pathogenic fungi generates a huge amount of economic losses worldwide. Different species of Penicillium spoil various foodstuffs and produce mycotoxins, alkaloids and other harmful cellular metabolites in the food. Presently, synthetic fungicides, mainly used for fungal diseases control, are associated with harmful impacts on the environment and consumer health. Hence, non-fungicide based eco-friendly and commercially viable alternative is proposed for ensuring food safety. In recent years, the safer options that have been explored include microbe mediated biological control, botanical pesticides, use of generally regarded as safe (GRAS) compounds, and innovative physical approaches including cold plasma, and pulsed light techniques. These emerging technologies could be utilized in the multiple hurdle concept of disease management for suppressing pathogens growth at different stages of spoilage development. This review, first of its kind, summarizes the exclusive information on Penicillium spp. induced spoilage, associated toxicological concerns and the potential of non-fungicide-based promising approaches for managing fungal wastage in the harvested horticultural commodities.
Article
Natural plant essential oils (EOs) can be used instead of synthetic fungicides because of human health concerns and environmental protection. In this study, the in vitro activity of some plants EOs against Penicillium digitatum, the cause of citrus green mold was evaluated during 8 days of incubation at 25°C. The EOs extracted from sweet orange (Citrus sinensis), lemon (Citrus limon), lime (Citrus aurantifolia), and sour orange (Citrus aurantium) fruit peel (500, 1000 and 2000 µl l-1 concentrations), cinnamon (Cinnamomum cassia) bark and summer savory (Satureja hortensis) aerial parts (400, 500 and 600 µl l-1 concentrations) were used on Penicillium digitatum mycelium. None of the EOs extracted from tested citrus in this study could inhibit mycelial growth completely even at concentration of 2000 µl l-1. The best results were obtained with cinnamon and summer savory EOs at concentration of 500 and 600 µl l-1. So, based on the results, cinnamon and summer savory EOs can be ideal candidates to replace the synthetic fungicides to control postharvest green mold of citrus fruit. GC-MS analysis showed that the most abundant of all constituents in EO extracts were carvacrol and γ-terpinene in summer savory and (E)-cinnamalde-hyde in cinnamon.
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The different modes of action of three isolated epiphytic yeast species (Metschnikowia citriensis FL01T and FL02, Candida oleophila FL14 and Pseudozyma antarctica FL17) against Penicillium digitatum and Penicillium italicum were investigated, and they showed better biocontrol efficacy than the P. membranaefaciens strain. These yeast species could be divided into two general classes according to their mechanisms against pathogens: species that caused growth inhibition of pathogens, which were mostly well-adapted to the wound environment, including M. citriensis FL01T and FL02 and C. oleophila FL14; species that caused severe cell damage and lysis, similar to P. antarctica FL17. An important mechanism involved in the biocontrol activity of P. antarctica FL17, which showed high lytic enzymes activity responsible for fungal cell wall degradation, was direct parasitism. The biofilm formation, the adhesion to mycelia, and the iron depletion were hypothesized as the key action mechanisms of M. citriensis FL01T and FL02. The induction of host resistance and quick growth to colonize wounds played essential roles in the biocontrol activity of C. oleophila FL14. This study indicates that excellent biocontrol yeasts involve multiple modes of action, but yeasts with different morphological characteristics vary greatly in their key mechanisms of action.
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The yeast Pichia membranaefaciens has antagonistic effects against a wide range of phytopathogenic fungi that cause postharvest fruit decay. This work evaluated the effects of P. membranaefaciens on the reactive oxygen species (ROS) metabolism and disease control in harvested citrus fruit (Citrus sinensis L Osbeck). The lesion diameter caused by Penicillium italicum and Penicillium digitatum on citrus fruit was remarkably reduced when the fruit was point-inoculated or dipped in a suspension of P. membranaefaciens at 1 x 10(8) CFU mL(-1). The application of P. membranaefaciens on citrus fruit enhanced the activity of superoxide dismutase, ascorbate peroxidase, and glutathione reductase, as well as the levels of hydrogen peroxide, the superoxide anion and glutathione, but inhibited the decreasing ascorbic acid content. Furthermore, catalase activity was decreased by the same treatment. These results indicated that yeast treatment induced the synthesis of antioxidant enzymes which might have antagonistic effects against postharvest green and blue mold infection in citrus fruit.
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The aim of this study was to assess the potential of microbial antagonists to control the growth and mycotoxin production by toxigenic fungal strain Aspergillus niger. Mycotoxins are secondary metabolites that produce acute and chronic effects on human and animal health. Among the mycotoxins of great interest produced by Aspergillus are ochratoxins and aflatoxins. Ochratoxin is considered to be nephrotoxic, teratogenic, immunotoxic, and probable human carcinogen. From this group, ochratoxin A is found in wheat, corn, grapes, raisins, wines and wine vinegars, cheese and meat products of animals fed with contaminated grains. Six microbial strains, two Bacillus, one Trichoderma and three Pseudomonas were evaluated for their potential as biocontrol agents. The antifungal activity of extracellular compounds released by bacterial strains was investigated by dry matter determination, microscopic observations, and enzyme linked immunosorbent assay (ELISA). Out of tested strains, B. amyloliquefaciens 1014 cultures produces metabolites with higher antifungal activity against A.niger. The active extracellular metabolites were partial characterized as referring to thermal stability and their production was optimized by varying the composition of the culture medium. Our results revealed that the metabolites from B. amyloliquefacines 1014 are thermostable and they are able to conserve the antifungal activity after sterilization. Keywords : Aspergillus niger, Bacillus sp., biocontrol, metabolites, antifungal activity
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One of the main problems affecting the citrus industry worldwide is caused by fungal diseases at postharvest stage. This leads to huge amounts of lemon fruit being unnecessarily discarded which contributed to the overall generation of agricultural wastes. Synthetic fungicides are nowadays the major agents used to control diseases of fungal origin. However, long-term and uncontrolled usage may lead to environmental problems such as growing restrictions that are mainly due to its toxicity. Among biocontrol agents, killer yeasts appear as efficient candidates especially for combating fungal postharvest decay in lemons.
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Paenibacillus polymyxa HT16 was evaluated for its ability to reduce white rot disease caused by Coniella diplodiella. HT16 showed significant inhibitory effects on C. diplodiella in vitro, reducing white rot disease in ‘Kyoho’ and ‘Thompson Seedless’ table grape varieties by more than 40% after inoculation. Liquid cultures were more effective than washed cell suspensions or cell-free supernatants, and a higher content of, and longer incubation time with, strain HT16 were more effective in reducing disease incidence. The spore germination rate and mycelial morphology of C. diplodiella were adversely affected by HT16. These results suggested that HT16 may be a promising biocontrol agent against preharvest and postharvest decay in table grapes.
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Considering the losses caused by post-harvest anthracnose in sweet pepper chili and ineffectiveness of control measures currently used, this study had the objective of evaluate the antagonistic potential in vitro and in vivo of fifteen isolates of yeast to Colletotrichum sp., the causal agent of anthracnose on pepper. By calculating the percentage growth inhibition of the fungus treatment compared to the control tests in vitro and determining the size of lesions via the measurement of lesion length in both directions diametrically affixed in vivo tests. Yeasts who obtained the best result in controlling anthracnose were identified by characteristic macroscopic, microscopic, physiological, biochemical and molecular taxonomy. In this study, the yeast isolates 13E and 13A1, which obtained the best results in controlling the pathogen both in vitro and in vivo of the species Rhodotorula glutinis. © 2015, Universidade Federal de Uberlandia. All rights reserved.
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Citrus is considered to be one of the major fruit crops produced worldwide. Mandarin orange (Citrus reticulata Blanco) is most common among the citrus fruits grown in India. It occupies nearly 50% of total citrus area and its maximum production is in India. Mandarin orange is a seasonal fruit and perishable by nature and around 30% of harvests are lost every year at the postharvest stage. This loss is mainly due to microbial infections on the fruits during transit, storage and marketing. In addition, immaturity and over-maturity at harvest, mechanical damage during harvest, transport and during distribution and water loss (wilting) due to poor handling systems further contribute to the annual loss. Lack of proper storage facilities is another important factor contributing to this unfortunate annual loss. Common control measures include the application of chemical fungicides, physical/mechanical methods and biocontrol strategies. In this review an attempt has been made to provide a comprehensive coverage of the postharvest damages and postharvest management strategies for mandarin (Citrus reticulata Blanco).
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Dip treatment of wounded pear (Pyrus communis) fruit (cvs. Anjou, Bosc, Bartlett, and Red Bartlett) with a saprophytic strain of Pseudomonas syringae (L-59-66) provided complete or partial control of gray mold (Botrytis cinerea) and blue mold (Penicillium expansum) during storage at 18 C for 5 days or 1 C for 30 days. Cultivar, wound type, and storage temperature significantly affected the efficacy of the treatment. Control of both diseases as high as 100% was achieved in many tests with the addition of L-59-66 to a final concentration of 5.4 × 10 8 cfu/ml in the inocula (10 4 conidia per milliliter) of the pathogens (.)
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Control of citrus blue mold, caused by Penicillium italicum, was evaluated on artificially inoculated oranges immersed in water at up to 75°C for 150 s; in 2 to 4% sodium carbonate (wt/vol) at 20 or 45°C for 60 or 150 s; or in 1 to 4% sodium bicarbonate at room temperature for 150 s, followed by storage at 20°C for 7 days. Hot water controlled blue mold at 50 to 55°C, temperatures near those that injured fruit, and its effectiveness declined after 14 days of storage. Sodium carbonate and sodium bicarbonate were superior to hot water. Temperature of sodium carbonate solutions influenced effectiveness more than concentration or immersion period. Sodium carbonate applied for 150 s at 45°C at 3 or 4% reduced decay more than 90%. Sodium bicarbonate applied at room temperature at 2 to 4% reduced blue mold by more than 50%, while 1% was ineffective. In another set of experiments, treatments of sodium bicarbonate at room temperature, sodium carbonate at 45°C, and hot water at 45°C reduced blue mold incidence on artificially inoculated oranges to 6, 14, and 27%, respectively, after 3 weeks of storage at 3°C. These treatments reduced green mold incidence to 6, 1, and 12%, respectively, while incidence among controls of both molds was about 100%. When reexamined 5 weeks later, the effectiveness of all, particularly hot water, declined. In conclusion, efficacy of hot water, sodium carbonate, and sodium bicarbonate treatments against blue mold compared to that against green mold was similar after storage at 20°C but proved inferior during long-term cold storage.
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Mechanisms involved in the biological suppression of infection and inoculum potential ofBotrytis cinerea are numerous and variable and the involvement of two or more mechanisms has been demonstrated in several systems. Reported combinations include antibiosis with enzyme degradation ofB. cinerea cell walls; competition for nutrients followed by interference with pathogenicity enzymes of the pathogen or with induced resistance; and alteration of plant surface wettability combined with antibiosis. Since germinatingB. cinerea conidia are dependent on the presence of nutrients, competition for nutrients is regarded as important in systems where biocontrol is involved. Conidial viability and germination capacity are also potentially affected by the presence of antibiotics produced by biocontrol agents and present in the phyllosphere. Slower in action are mechanisms involving induced resistance in the host plant and production of hydrolytic enzymes that degradeB. cinerea cell walls. The latter has been demonstrated much more convincinglyin vitro than in the phyllosphere. Biocontrol in established lesions and reduction of sporulation on necrotic plant tissues is a means to minimize the pathogen inoculum. Key wordsantibiosis-attachment-bio-control-competition-germination-hydrolytic enzymes-induced resistance-mycoparasitism-pathogenesis-pathogenicity related-sclerotium-sporulation-survival-wettability
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Spoilage of fruits and vegetables after harvest often causes losses as great as 25–50% of the harvested crop. Much of this is due to rot micro-organisms which are currently controlled by refrigeration and fungicides. A number of bacterial and fungal antagonists have been found that can effectively control post-harvest rots of peaches, citrus, apples, grapes and tomatoes. These antagonists have various modes of action that include antibiosis and/or competition for nutrients and space. The commercialization of some of these antagonists to control post-harvest decay of fruits and vegetables appears to be feasible and may present an alternative to synthetic pesticides.
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ABSTRACT Penicillium digitatum isolates (326), collected in California citrus groves and packinghouses, were assayed qualitatively for their sensitivity to imazalil, thiabendazole, and o-phenylphenol. Eighteen typical triple-resistant isolates, acquired in each of 3 years (1988, 1990, and 1994), were assayed quantitatively for their sensitivity to each of the three fungicides. No significant differences were found in the mean sensitivity of the isolates collected in different years. However, the proportion of isolates that were resistant to all three fungicides increased from 43% in 1988 to 77% in 1990 and 74% in 1994. Imazalil-resistant biotypes of P. digitatum were isolated frequently in California packinghouses, while resistant P. italicum was rare. No fungicide-resistant biotypes of either species were collected from citrus groves. Wild-type P. italicum was slightly less sensitive than wild-type P. digitatum to all three fungicides. The concentration of imazalil producing 50% growth inhibition (EC(50)) was three times greater when the age of the P. digitatum assay inoculum was increased from 12 to 24 h. Activity of imazalil increased with pH of the assay medium in the range pH 5.1 to 5.9, reflecting the greater concentration of dissociated imazalil at the higher pH value.
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Cryptococcus laurentii was evaluated for its activity in reducing postharvest blue mould decay of pear caused by Penicillium expansum. Washed cell suspensions of yeast controlled blue mould better than yeast in culture broth. Treatment of wounds with autoclaved cultures or cell-free culture filtrate did not prevent decay. There was a negative correlation between concentrations of the yeast cells and infectivity of the pathogens: at concentrations of yeast at or above 1 × 109 colony forming units (CFU) ml–1 and pathogen spores suspension of 5 × 104 spores ml–1, blue mould was completely inhibited after 7 d of incubation at 25°C, and was almost inhibited after 30 d incubation at 2°C followed by 7 d at 20°C. The interval between inoculation with the pathogen and application of the antagonist significantly influenced the efficacy of biocontrol. Efficacy was maintained when C. laurentii was applied simultaneously or prior to inoculation with P. expansum but reduced if applied after inoculation with P. expansum. Rapid colonization of the yeast in wounds was observed during the first 3 d at 20°C, and then the populations stabilized for the remaining storage period. On pear wounds kept at 4°C, the increase in population density of C. laurentii was lower than at 20°C, but rose over 15 d after application of the antagonist to approx. 107 CFU wound–1.
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A yeast, strain 138 of Kloeckera apiculata, isolated from the surface of grapes, was evaluated for its activity in reducing postharvest decay of grape, peach, and apple fruits. In an artificial infection assay in which detached grapes were immersed in an aqueous suspension of yeast cells (5 × 10⁸ cfu/ml) and spray-inoculated with 10³ sporangiospores per milliliter of Rhizopus stolonifer, strain 138 reduced decay, whereas strain 87 (= US-7) of Candida guilliermondii did not. In an assay in which naturally infected fruits were immersed in yeast suspensions, both strains were effective in reducing postharvest decay of grapes caused by R. stolonifer; however, neither yeast was effective in reducing decay caused by Aspergillus niger. Three strains of K. apiculata obtained from other sources were compared to strain 138 and strain 87 for activity against Rhizopus rot of peach and gray mold of apple. Fruit wounds were pretreated with water-suspended yeast cells (10⁸ cfu/ml) and inoculated with 10³ sporangiospores of R. stolonifer per milliliter or 10⁵ conidia of Botrytis cinerea per milliliter. Two of three strains of K. apiculata were as effective as strains 138 and 87 for the control of Rhizopus rot of peach. All strains were equally effective in reducing gray mold of apple. Control of gray mold and blue mold of apples and Rhizopus rot of peaches was enhanced when strain 138 was applied as an aqueous suspension (10⁸ cfu/ml) in 2% CaCl2. This method did not reduce the incidence of brown rot of peach, caused by Monilinia fructicola; however, decreased lesion diameter was observed in fruit treated with yeast and CaCl2.
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A new yeast antagonist, Pichia membranefaciens, isolated from wounds of peach fruit, was evaluated for its biocontrol capability against Rhizopus stolonifer on nectarine fruits at different temperatures and with other treatments. P. membranefaciens at 5 x 108 CFU/ml of washed-cell suspension completely inhibited Rhizopus rot in nectarine wounds artificially inoculated with 5 x 104 spores per ml at 25, 15, and 3°C. A culture filtrate of the yeast antagonist failed to provide any protection against Rhizopus rot in nectarine fruits. The yeast mixed with iprodione at 100 μg a.i./ml gave better control of R. stolonifer than either yeast or iprodione alone. A solution of 20 g CaCl2 per liter enhanced the efficacy of P. membranefaciens (107 to 108 CFU/ml) as an aqueous suspension. Rapid colonization of the yeast in wounds was observed during the first 48 h at 25 and 15°C. P. membranefaciens at 5 x 108 CFU/ml was effective when applied 0 to 72 h before the pathogen, while at 1 x 108 CFU/ml, its efficacy was best when applied 24 to 48 h prior to inoculation with R. stolonifer. However, its efficacy was significantly reduced when the yeast was applied simultaneously with the pathogen, with disease incidence of 60% and lesion diameter of 37 mm.
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Six yeast strains isolated from the surface of pear fruits were evaluated for their ability to control postharvest blue mold (caused byPenicillium expansum) on Golden Delicious apple fruits. All strains significantly reduced blue mold incidence and severity when applied simultaneously with the pathogen.Cryptococcus infirmo-miniatusstrain YY6 andCryptococcus laurentiistrain HRA5 were the most effective, and populations in apple wounds increased approximately 1.2 log units within 10 days at 0°C and approximately 1.4 log units in 2 days at 5, 10, or 20°C. Control of blue mold by these two yeasts alone or in combination with a low dose of thiabendazole (15 μg/ml) was tested at 5, 10, and 20°C. Yeasts combined with thiabendazole controlled the disease significantly better at all temperatures (except at 10°C during 1994) than the low dose of thiabendazole alone, and the control was comparable to that achieved using a commercially recommended high dose of thiabendazole (525 μg/ml).C. infirmo-miniatuscontrolled disease incidence better thanC. laurentiiat 5, 10, and 20°C during 1993 and 1994. On sweet cherry,C. infirmo-miniatusorC. laurentiicombined with a low dose (20 μg/ml) of iprodione controlled brown rot caused byMonilinia fructicolaas did a high dose (1175 μg/ml) of iprodione.
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Aspire, a formulation of the yeast Candida oleophila registered for postharvest application to citrus for the control of green mold (Penicillium digitatum), competes with the pathogen for nutrients at injuries to prevent infection. A major factor affecting efficacy is how quickly and well the yeast colonizes injuries to the fruit surface, including minor injuries involving only oil vesicles. Colonization of puncture-related injuries that either encompassed oil glands or individually ruptured glands was achieved within 1–2 days at 21°C. Colonization of puncture injuries by C. oleophila was comparable after 2 days at 21 and 30°C, but no colonization occurred at 13°C. Ruptured oil glands were colonized more effectively if treated 7 h after injury rather than immediately. Peel oil was toxic to cells of C. oleophila but not to spores of P. digitatum. Candida oleophila colonized punctures more uniformly than individually damaged oil glands, and provided more effective control of green mold originating at punctures than at oil gland injuries. Incubating treated fruit at 30°C for 2 days before storage at 21°C enhanced the control of green mold, and control was significantly improved by the addition of Aspire in one of two trials.
Article
Oranges were inoculated with spores of Penicillium digitatum, the citrus green mold pathogen, and immersed 24 h later in heated soda ash (Na2CO3, sodium carbonate) solutions to control postharvest citrus green mold. Oranges were immersed for 1 or 2 min in solutions containing 0, 2, 4, or 6% (wt/vol) soda ash heated to 35.0, 40.6, 43.3, or 46.1 degrees C. After 3 weeks of storage at 10 degrees C, the number of decayed oranges was determined. Soda ash significantly controlled green mold in every test. The most effective control of green mold was obtained at 40.6 or 43.3 degrees C with 4 or 6% soda ash. The concentration of soda ash greatly influenced efficacy, whereas the influences of temperature or immersion period on soda ash efficacy were small. Solutions of 4 and 6% soda ash were similar in efficacy and provided superior control of green mold compared with 2% soda ash. The control of green mold by soda ash solutions heated to 40.6 or 43.3 degrees C was slightly superior to control by solutions heated to 35.0 or 46.1 degrees C. The control of green mold by 1-min immersion of inoculated oranges in heated soda ash solutions was inferior to immersion for 2 min, but the magnitude of the difference, particularly with 6% soda ash, was small. A second-order response surface model without interactions was developed that closely described the influence of soda ash concentration, temperature, and immersion period on efficacy. The efficacy of soda ash under commercial conditions was better than that predicted by the model, probably because under commercial conditions the fruit were rinsed less thoroughly with water after treatment than in laboratory tests. The primary finding of this work was that soda ash controlled 24-h-old green mold infections at commercially useful levels using shorter immersion periods and lower temperatures than those recommended by other workers for the use of soda ash on lemons. The oranges were not visibly injured in any test.
Article
At a concentration of 0.025% (w/v) chitosan-chloride inhibited spore germination of Botrytiscinerea, Penicillium expansum, and Candida saitoana. In contrast, at 0.5% (w/v) glycolchitosan inhibited spore germination of B. cinerea and P. expansum, but not the growth of C. saitoana in vitro or in apple wounds. The combination of C. saitoana with 0.2% glycolchitosan was more effective in controlling gray and blue mold of apple caused by B. cinerea and P. expansum, respectively, and green mold of oranges and lemons caused by P. digitatum than C. saitoana or 0.2% glycolchitosan alone. The level of control was similar to that obtained with the fungicide imazalil on oranges and lemons. C. saitoana in combination with 0.2% glycolchitosan reduced green mold incidence equally on light green and yellow lemons, while C. saitoana was more effective on light green lemons than on yellow lemons. When applied as a pretreatment, sodium carbonate enhanced the efficacy of all treatments tested against green mold with the greatest effect on light green lemons. Of the treatments tested, pretreatment with sodium carbonate followed by the combination of C. saitoana with 0.2% glycolchitosan was the most effective in controlling green mold of both light green and yellow lemons.
Article
This study examined the effect of volatile components of citrus fruit essential oils on P. digitatum and P. italicum growth. The hydrodistilled essential oils of orange (Citrus sinensis cvv. “Washington navel”, “Sanguinello”, “Tarocco”, “Moro”, “Valencia late”, and “Ovale”), bitter (sour) orange (C. aurantium), mandarin (C. deliciosa cv. “Avana”), grapefruit (C. paradisi cvv. “Marsh seedless” and “Red Blush”), citrange (C. sinensis x Poncirus trifoliata cvv. “Carrizo” and “Troyer”), and lemon (C. limon cv. “Femminello”, collected in three periods), were characterized by a combination of GC and GC/MS analyses. The antifungal efficacy of the oils was then examined at progressively reduced rates. Findings showed a positive correlation between monoterpenes other than limonene and sesquiterpene content of the oils and the pathogen fungi inhibition. The best results were shown by the citrange oils, whose chemical composition is reported for the first time, and lemon. Furthermore P. digitatum was found to be more sensitive to the inhibitory action of the oils.
Article
Biological control ofPenicillium digitatum on orange fruits with an isolate ofCandida famata (F35) obtained from fig leaves in Sardinia is reported. Inhibition values of from 90% to 100% in oranges were obtained in artificially wounded fruits, in terms of pathogen conidia concentration. Scanning electron microscope observations of the mode of action of the antagonist against the pathogen revealed rapid colonization of the fungal mycelium and the wounds, with lytic and phagocytic activity against the hyphae. With regard to the host-antagonist-pathogen interaction, it was observed that when the yeast was inoculated into the artificial wounds either alone or with the pathogen, it stimulated the fruit to produce phytoalexins (scoparone and scopoletin) in concentrations which varied significantly in relation to the time lag between inoculation with the antagonist and inoculation with the pathogen. The biosynthesis of scoparone in particular, four days after inoculation with the yeast only, was 124 μg/g fresh weight of the fruit, 12 times higher than in the non-inoculated wound tissues, while it decreased to 47 μg/g when F35 was inoculated at the same time asP. digitatum, and to 37 μg/g when the pathogen only was inoculated.
Article
The effect of temperature on inflorescence development and sex expression in two mono-embryonic ('Irwin' and 'Sensation'), and two poly-embryonic ('Nam Dok Mai' and 'Kensington') mango cultivars was studied. Trees were subjected to natural winter temperatures to induce flowering prior to transfer into controlled environment glasshouse rooms under day/night temperature regimes of 15/5, 20/10, 25/15 and 30/20°C for 20 weeks. Inflorescence development did not progress when trees were held at 15/5°C. Cooler temperatures (20/10°C) delayed the start of anthesis (42.4 d) compared with trees grown at 25/15°C (23 d) and 30/20°C (16.1 d). At 20/10°C, the delay in the start of anthesis was greatest for 'Sensation' (55.5 d) and least for 'Nam Dok Mai' (25.5 d) while at other temperatures there was little difference between cultivars. The distribution of hermaphrodite flowers within the inflorescence was independent of temperature with the highest percentage found in the apical half of the inflorescence. There was an inverse relationship between the length of the anthesis period and temperature, with anthesis occurring over 30 d at 20/10°C and reducing to fewer than 10 d at 30/20°C. Temperature also had an inverse effect on the total number of flowers per inflorescence with 619.6 ± 108.0 (mean for all cultivars) at 20/10°C decreasing to 431.3 ± 80.5 at 30/20°C.
Article
Clementine mandarins cv. 'Clemenules', artificially inoculated with Penicillium digitatum or Penicillium italicum, were immersed in 0, 2, or 3% (w/v) sodium carbonate (SC) solutions at 20, 45 or 50 degrees C for 60 or 150 s. Decay incidence was determined after 7 days of storage at 20 degrees C and 90% relative humidity (RH). Hot water (HW) at 45 or 50 degrees C did not satisfactorily control both diseases. SC significantly enhanced decay control compared to water alone at all temperatures and for all immersion periods. Heated SC solutions were more effective than solutions at 20 degrees C. A 150 s dip in 3% SC at 50 degrees C totally controlled both green and blue molds without noticeably injuring the fruit. SC at 50 degrees C significantly reduced the incidence of both green and blue molds on mandarins stored at 3.5 degrees C for 60 days. Both diseases were reduced by 40-60% on mandarins dipped for 60 or 150 s in 2 or 3% sodium bicarbonate (SBC) solutions at room temperature. The effectiveness of all HW, SC, and SBC treatments on clementines was inferior to that obtained on oranges or lemons in related previous work.
Article
ABSTRACT Interactions between CaCl(2), grapefruit peel tissue, Penicillium digitatum, and the yeast antagonist Pichia guilliermondii strain US-7 were investigated. Application of 68 or 136 mM CaCl(2) to grapefruit surface wounds reduced the incidence of green mold caused by Penicillium digitatum by 43 to 52%. In laboratory tests, a cell suspension (10(7) cells/ml) of Pichia guilliermondii containing either 68 or 136 mM CaCl(2) reduced the incidence of green mold from 27 to 3%. In large scale tests, dip application of 136 mM CaCl(2) with US-7 (10(7) cells/ml) significantly decreased the number of wounds infected by Penicillium digitatum. CaCl(2), with or without yeast cells, stimulated ethylene production in grapefruit tissue. Increasing concentrations of CaCl(2) resulted in decreased spore germination and germ tube elongation of Penicillium digitatum. Pectinolytic activity of crude enzyme preparations of Penicillium digitatum was also inhibited by the presence of increasing concentrations of CaCl(2). US-7 exhibited a strong ability to maintain cytosolic Ca(2+) homeostasis at levels that did not exceed 1.4 muM when exposed to 150 mM CaCl(2). On the other hand, strain 114 of Debaryomyces hansenii, which failed to give any protection against infection by Penicillium digitatum, showed reduced capacity to maintain Ca(2+) homeostasis. The effect of calcium in reducing infection of grapefruit wounds by Penicillium digitatum could be due to direct effects on host tissue (making cell walls more resistant to enzymatic degradation) or the pathogen (interfering with spore germination, growth, and inhibition of fungal pectinolytic enzymes). Alternatively, the ability of US-7 to maintain calcium homeostasis may allow it to grow or assist in its competitive ability in a microenvironment that, because of high levels of calcium ions, is inhibitory to growth of the green mold pathogen.
Article
Epiphytic microorganisms isolated from apples, pears and the surfaces of apple leaves were screened for antagonistic activity against Penicillium expansum (blue-mold), Botrytis cinerea (gray-mold) and Rhizopus nigricans (Rhizopus rot) on apple (Malus domestica). A total of 933 bacteria and yeasts were tested in primary screening against P. expansum. Ninety-two strains reduced the lesion size on apples by more than 50%, 72 of which were isolated from the surface of apples. For secondary screening against P. expansum, B. cinerea and R. nigricans, 31 strains were selected. The most promising isolate, CPA-1, was identified as Candida sake. This yeast, isolated from apples in storage season was very effective against all three diseases. Wounded Golden Delicious apples protected with the yeast suspension at a concentration of 2.6 x 10(6) CFU/ml and inoculated with conidia of B. cinerea and R. nigricans of 10(5) and 10(4) conidia/ml, respectively, did not develop rot. Complete control of P. expansum was obtained at the same concentration of the antagonist with a pathogen inoculum concentration of 10(3) conidia/ml. This strain, also provided excellent control of rot development under cold storage conditions. The strain of Candida sake can grow actively in aerobic conditions. In drop-inoculated wounds of apples, the populations of C. sake increased by more than 50-fold during the first 24 h at 20 degrees C. The maximum population of C. sake on apple wounds was the same at 20 as at 1 degrees C and was recovered after three and twenty days, respectively.