Antagonistic Yeast Research Articles

Whole-genome sequencing of Cryptococcus podzolicus Y3 and data-independent acquisition-based proteomic analysis during OTA degradation

Cryptococcus podzolicus Y3 is an antagonistic yeast that can control postharvest diseases of crops and mycotoxins, which is potentially valuable for ensuring food safety. Our previous study showed that C. podzolicus Y3 can efficiently degrade ochratoxin A (OTA), one of the harmful mycotoxins in the environment and food. However, the genomic information of C. podzolicus Y3 and its protein expression profile during OTA degradation are not available. In this study, whole-genome sequencing of C. podzolicus Y3 was analyzed. Protein expression during OTA degradation was investigated by the data-independent acquisition (DIA) technique. The genome size of C. podzolicus Y3 was about 29,181,249 bp length with 58.79% GC content and identified with 17 scaffolds, 9090 coding regions and 127 non-coding regions. The DIA identified 4315 proteins during OTA degradation, among which 101 proteins were significantly up-regulated and 116 were down-regulated. The differentially expressed proteins were mainly involved in reduced glutathione metabolism, phosphatidylinositol signaling system and mitogen-activated protein kinase signaling pathway, calcium ion homeostasis, endoplasmic reticulum protein processing and fatty acid metabolism. Our results provide the genome information of C. podzolicus Y3 for further functional researches. In addition, this study has revealed the toxicity and stress response mechanism of C. podzolicus Y3 during OTA degradation at the protein level.

Controlling black spot of postharvest broccoli by Meyerozyma guilliermondii and its regulation on ROS metabolism of broccoli

Black spot caused by Alternaria brassicicola is one of the most common fungal diseases of postharvest broccoli. The present study investigated the biocontrol efficacy of Meyerozyma guilliermondii against black spot of postharvest broccoli and the mechanisms involved in the enhanced disease resistance of broccoli based on its effects on reactive oxygen species (ROS) metabolism. Our investigation proved that M. guilliermondii could decrease the disease index of postharvest broccoli caused by A. brassicicola. This antagonistic yeast could potentially increase peroxidase, catalase and superoxide dismutase activities, and the activities of enzymes involved in ascorbate–glutathione cycle and glutathione peroxidase cycle, such as ascorbate peroxidase, glutathione peroxidase and glutathione reductase. Furthermore, the contents of non-enzymatic antioxidants, including ascorbic acid and glutathione, were enhanced by this yeast. Accordingly, the accumulation of ROS, including hydrogen peroxide (H2O2) and superoxide anion (O2–), was reduced by M. guilliermondii, as well as malondialdehyde amount which was one of the membrane lipid peroxides. Our results suggested that M. guilliermondii could improve the activities of ROS scavenging enzymatic system and the levels of antioxidant substances to scavenge excessive ROS, and then protect cells from oxidative damage, which enhanced the disease resistance of broccoli to pathogens. Overall, our study provides a new disease control strategy for postharvest broccoli by improving the ability of ROS scavenging to resist pathogens.

Antifungal effects of volatile compounds produced by Tetrapisispora sp. strain 111A-NL1 as a new biocontrol agent on the strawberry grey mold disease.

An antagonistic yeast strain was isolated from the strawberry fruit cv. Paros, and its antifungal properties against Botrytis cinerea causal agent of strawberry grey mold disease were evaluated under in vitro and in vivo experiments. The isolate was tentatively identified as Tetrapisispora sp. strain 111A-NL1 based on phenotypic characteristics and sequence analysis of D1/D2 domains of the 26S rRNA gene. Volatile organic compounds (VOCs) produced by the 111A-NL1 strain inhibited the mycelial growth of fungal pathogen (75.19%) and conidial germination (63.34%); however, inhibition percentage of mycelial growth of pathogen by dual culture test was less (19.49%). Also, the strain produced pectinase, siderophore, chitinase, IAA, as well as gibberellin, and could solubilize phosphate. Additionally, the disease severity of strawberry grey mold was decreased by employing living cells and volatile metabolites methods by 47.61% and 74.05%, respectively, in comparison with untreated control seven days after inoculation. Therefore, its mode of action might consist of antibiosis and VOCs production by yeast strain 111A-NL1 against B. cinerea. The VOCs released by strain 111A-NL1 were analyzed, and thirty-three chemical compounds were determined by gas chromatography-mass spectroscopy (GC-MS). Out of them, Decane (12.79%), Squalene (9.60%), Undecane (7.98%), Benzene, 1,2,3-trimethyl- (7.67%), Nonane, 2,6-dimethyl- (5.69%), Benzene, 1-ethyl-3-methyl- (5.55%), Mesitylene (4.17%), and Phenylethyl Alcohol (3.33%) were the major components. In addition, the selected strain reduced natural decay incidence and weight loss of fruit, and preserved quality parameters of strawberry fruit including firmness, soluble solids content, and titratable acidity. This research averred, for the first time, that the creation of VOCs by Tetrapisispora sp. strain 111A-NL1 could play an essential role as a biofumigant in the antifungal activity against strawberry grey mold.

The application of antagonistic yeasts and bacteria: An assessment of in vivo and under field conditions pattern of Fusarium mycotoxins in winter wheat grain

Bacteria of the genus Sphingomonas, Aureobasidium pullulans yeast-like fungus and yeast Debaryomyces hansenii naturally colonize wheat grain. Selected isolates of these microorganisms, antagonistic against Fusarium spp., can be applied to wheat spikes to complement chemical control methods. The aim of this study was to determine the content of Fusarium mycotoxins in winter wheat grain in vivo and under field conditions, and to analyze the interactions between antagonistic microorganisms and F. culmorum and F. avenaceum pathogens in dual cultures. Seventeen toxic metabolites produced by Fusarium fungi were identified in grain: deoxynivalenol, deoxynivalenol-3-glucoside, culmorin, 15-hydroxyculmorin, 5-hydroxyculmorin, HT-2 toxin, nivalenol, nivalenol-3-glucoside, aurofusarin, enniatins, zearalenone, moniliformin, equisetin, and apicidin. Integrated fungicide and biological treatments decreased deoxynivalenol levels in grain in the field conditions from 141.36 to 72.76 μg/kg. Deoxynivalenol was not detected in grain treated with D. hansenii suspension, and culmorin content was 38 times lower than in unprotected grain. Fungicides and integrated treatments involving D. hansenii also decreased enniatin A1 content by 76.61 and 48.17%. In vitro yeasts considerably reduced moniliformin and enniatin concentrations by 7.67–92.87%. Antagonistic microorganisms, which inhibit the growth of Fusarium fungi through antibiosis and competition for nutrients, can effectively reduce the production of selected Fusarium toxins when combined with fungicides in the integrated approach.

Applying antagonist yeast strains to control mango decay caused by Lasiodiplodia theobromae and Neofusicoccum parvum

Successfully inserting a biocontrol agent (BCA) in the integrated management of mango fruit decay can be affected by several factors, including BCA inoculum density and the timing of its application. This study focused on improving biocontrol efficacy by adjusting doses of a BCA formulation and the timing for the substitution of synthetic fungicides sprays. Technical grade formulations containing increasing doses (104 – 108) of the yeast strains Saccharomyces sp. ESA45, S. boulardii ESA46, Saccharomyces sp. ESA47, and Pichia kudriavzeviii CMIAT171 were applied to mango fruits, followed by the inoculation of Lasiodiplodia theobromae and Neofusicoccum parvum in artificial wounds. Non-linear regression analysis of increasing doses of the BCAs against severity data and curve slopes comparison showed a significant difference in control efficiency among yeast strains. A log-linear regression model showed that ESA45 and CMIAT171 exhibited lower doses to achieve 90% control. Two field experiments were conducted in commercial mango orchards cultivated with the cultivars ‘Kent’ and ‘Palmer’. Starting the substitution of fungicides by BCA in fruit onset and when fruits achieved egg size resulted in lower fruit rot incidence and severity during cold storage and shelf life. The complete substitution of fungicides during fruit development did not show consistent performance. Similarly, applying BCA formulation only at the end of fruit development did not hinder the establishment of quiescent infections.

Influence of Marine Yeast Debaryomyces hansenii on Antifungal and Physicochemical Properties of Chitosan-Based Films.

Chitosan-based film with and without antagonistic yeast was prepared and its effect against Penicillium italicum was evaluated. The biocompatibility of yeast cells in the developed films was assessed in terms of population dynamics. Furthermore, the impact on physicochemical properties of the prepared films with and without yeast cells incorporated were evaluated in terms of thickness, mechanical properties, color and opacity. Chitosan films with the antagonistic yeast entrapped exhibited strong antifungal activity by inhibiting the mycelial development (55%), germination (45%) and reducing the sporulation process (87%). Chitosan matrix at 0.5% and 1.0% was maintained over 9 days of cell viability. However, at 1.5% of chitosan the population dynamics was strongly affected. The addition of yeast cells only impacted color values such as a*, b*, chroma and hue angle when 1.0% of chitosan concentration was used. Conversely, luminosity was not affected in the presence of yeast cells as well as the opacity. Besides, the addition of antagonistic yeast improved the mechanical resistance of the films. The addition of D. hansenii in chitosan films improve their efficacy for controlling P. italicum, and besides showed desirable characteristics for future use as packaging for citrus products.

Transcriptome analysis of asparagus in response to postharvest treatment with Yarrowia lipolytica

Our previous study showed that Yarrowia lipolytica can be a potential postharvest treatment for Fusarium disease control in asparagus. In light of this, our current study is further interested in exploring the molecular mechanisms involved in the disease control. RNA-Seq analysis of asparagus was performed 3 days after inoculation. Transcriptome analysis revealed that the signal transduction pathways of salicylic acid (SA) and jasmonate (JA) in asparagus were triggered by Y. lipolytica. Simultaneously, Ca2+ signal transduction was activated (CML19) and reactive oxygen output (RBOHE, RBOHF) was triggered. These changes triggered several genes that play important roles in plant disease resistance, including PR1 genes, PGIP2, PLP2, and FMO1. In addition, antioxidant genes (PER genes, PNC1, Sb03g046810) and glutathione S-transferase (GST) genes, genes assigned to secondary metabolites (CCR, CAD, DIR21, PAL, PER genes, CYP75B2, CYP73A13, UGT92A1, UGT73C6, F3H-1, CCoAMT5, ALDH2C4, and BGLU12) induced the ability of asparagus to improve disease resistance. Genes involved in the EMP-TCA pathway (FRK2, PFK3 and MSTRG.32630) were amplified, which can provide energy for the defense response, and genes related to the cell wall and membrane (SBH1, SBH2, LRX, and PERK) were induced to improve the physical barriers against the pathogen. The results of the study can serve as a reference for further investigation of the molecular mechanisms involved in the interaction between plants and antagonistic yeasts and can contribute to the practical application of biocontrols.

Transcriptomic analysis of the mechanisms involved in enhanced antagonistic efficacy of Meyerozyma guilliermondii by methyl jasmonate and disease resistance of postharvest apples

The biological control ability of the yeast, Meyerozyma guilliermondii, in restaining Penicillium expansum infection in apples, has been reported to be enhanced by methy jasmonate (MeJA). Our previous research unveiled the possible physiological biocontrol mechanisms of the yeast; however, the related molecular mechanisms were unclear. This study aimed to investigate the possible molecular mechanisms behind the enhanced biological control efficacy of M. guilliermondii cultured with MeJA through transcriptomic approaches. The transcriptome analysis of MeJA cultured M. guilliermondii indicated that MeJA induced changes in oxidative stress response, energy metabolism, cell wall synthesis and stability and cell growth. Meanwhile, transcriptomic analysis of apples treated with M. guilliermondii and MeJA cultured M. guilliermondii was also investigated. Our results witnessed that MeJA cultured M. guilliermondii enhanced the cell wall synthesis, antioxidant activity, plant disease resistance, increased peroxisome proliferation, energy metabolism, phenylpropane metabolism and other pathways of apples. Expression levels of PPO, EXPA1, TFT6, GHR5, CYP73 and other genes were increased, which enhanced the apple's stability, antioxidant, stress resistance and energy metabolism. This study will provide a theoretical basis for improving the biocontrol efficacy of antagonistic yeast cultured with MeJA.

Efficacy of the Yeast Wickerhamomyces anomalus in Biocontrol of Gray Mold Decay of Tomatoes and Study of the Mechanisms Involved.

Gray mold decay is a widespread postharvest disease in tomato that results from infection by the pathogen Botrytis cinerea, leading to huge economic losses. The objective of this study was to select the most effective antagonistic yeast to control tomato gray mold from six potential biocontrol agents and to investigate the possible control mechanism. The results showed that the yeast Wickerhamomyces anomalus was the most effective in inhibiting B. cinerea among the six strains both in vivo and in vitro on tomato, with a colony diameter of 11 mm, a decay diameter of 20 mm, and the lowest decay incidence (53%)—values significantly smaller and lower than the values recorded for the control group and the other yeasts. The efficacy of the control depended on the increase in yeast concentration, and the decay incidence and lesion diameter were reduced to 31%, 28% and 7 mm, 6 mm, respectively, when treated with 1 × 108 and 1 × 109 cells/mL W. anomalus. In addition, W. anomalus was able to rapidly colonize and stably multiply in tomato, occupying the space to control pathogen infection. W. anomalus was also able to motivate the defense mechanism of tomato with stimulation of defense-related enzymes PPO, POD, APX, and SOD and promotion of the content of total phenols and flavonoid compounds. All these results suggest that W. anomalus exhibited exceptional ability to control gray mold in tomato.

Efficacy of Meyerozyma guilliermondii in controlling patulin production by Penicillium expansum in shuijing pears

Meyerozyma guilliermondii is an antagonistic yeast that efficiently controls the blue mold decay of pears and potentially degrades patulin in vitro conditions. However, the possible patulin controlling efficacy of M. guilliermondii in pears remains unclear. In this study, the patulin controlling effect of M. guilliermondii in pears was investigated. The results showed that M. guilliermondii could effectively control patulin content production by Penicillium expansum in shuijing pear wounds from 3 d to 11 d. However, M. guilliermondii has a poor patulin control effect on fragrant pear and dangshan pear wounds. The patulin degradation ability of M. guilliermondii in shuijing pear wounds increased with the higher concentration of the yeast cells, and 1 × 108 cells/mL showed the best patulin control effect. In shuijing pears, M. guilliermondii could effectively control patulin at 20 °C and 4 °C in wounds as well as the whole fruits. Our results provide a safe and efficient strategy to detoxify patulin using M. guilliermondii, thereby limitting the risks of patulin in shuijing pears.

Biological Control of Fusarium culmorum, Fusarium graminearum and Fusarium poae by Antagonistic Yeasts.

The genus Fusarium is considered to be one of the most pathogenic, phytotoxic and toxin-producing group of microorganisms in the world. Plants infected by these fungi are characterized by a reduced consumer and commercial value, mainly due to the contamination of crops with mycotoxins. Therefore, effective methods of reducing fungi of the genus Fusarium must be implemented already in the field before harvesting, especially with alternative methods to pesticides such as biocontrol. In this study we identified yeasts that inhibit the growth of the pathogenic fungi Fusarium culmorum, F. graminearum and F. poae. Tested yeasts came from different culture collections, or were obtained from organic and conventional cereals. The greater number of yeast isolates from organic cereals showed antagonistic activity against fungi of the genus Fusarium compared to isolates from the conventional cultivation system. Cryptococcus carnescens (E22) isolated from organic wheat was the only isolate that limited the mycelial growth of all three tested fungi and was the best antagonist against F. poae. Selected yeasts showed various mechanisms of action against fungi, including competition for nutrients and space, production of volatile metabolites, reduction of spore germination, production of siderophores or production of extracellular lytic enzymes: chitinase and β-1,3-glucanase. Of all the investigated mechanisms of yeast antagonism against Fusarium, competition for nutrients and the ability to inhibit spore germination prevailed.

Combination of yeast antagonists and Acibenzolar-S-Methyl reduced the severity of Fusarium head blight of wheat incited by Fusarium graminearum sensu stricto

The combination of yeast antagonists and Acibenzolar-S-Methyl (ASM) was tested against Fusarium graminearum on a spring wheat cultivar PAN3471. Two strains of Papiliotrema flavescens (Strains WL3 and WL6) and a strain of Pseudozyma sp. (MGO1) were combined with full strength ASM at anthesis, half strength ASM at anthesis and quarter strength ASM at late boot stages. The yeast and ASM treatments were applied prior to F. graminearum inoculation and disease progress was assessed over time. The combination of yeast and ASM treatments effectively reduced Fusarium Head Blight (FHB) severity and deoxynivalenol (DON) concentration compared to when the treatments were used alone. A positive correlation was observed between the Area Under Disease Progress Curve (AUDPC) and Percentage Seed Infection (PSI) (r = 0.44) whereas a negative correlation was observed between AUDPC and Hundred Seed Weight (HSW) (r = -0.77) and PSI and HSW (r = -0.44). The best combination treatment providing the highest reduction in final disease severity (41.83%), high HSW and moderate PSI was 0.075 g/l ASM at anthesis plus P. flavescens strain WL3. The highest DON reduction (19.35%) was by the treatment 0.075 g/l ASM at anthesis plus P. flavescens strain WL6. The best treatment was P. flavescens combined with 0.075 g/l ASM at anthesis. Although Pseudozyma sp. strain MGO1 did not provide the best FHB and DON reduction, its combination with ASM application improved disease control efficacy. To the best of our knowledge, this study presents the first report of the combination of P. flavescens and ASM in the management of FHB caused by F. graminearum in wheat plants.

Enhancement of Biocontrol Efficacy of Pichia kudriavzevii Induced by Ca Ascorbate against Botrytis cinerea in Cherry Tomato Fruit and the Possible Mechanisms of Action

ABSTRACTThis study investigated the effect of Ca ascorbate on the biocontrol efficacy of Pichia kudriavzevii and the possible mechanisms. The results indicated that the biocontrol activity of P. kudriavzevii was significantly enhanced by 0.15 g L−1 of Ca ascorbate, with higher growth rates of yeast cells in vitro and in vivo. The antioxidant enzyme activity in P. kudriavzevii, including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), were improved by Ca ascorbate and reached the maximum at 96 h, 96 h, and 72 h, respectively. The expression of the antioxidant enzyme-related genes CAT1 (8.55-fold) and SOD2 (7.26-fold) peaked at 96 h, while PRXIID (2.8-fold) peaked at 48 h, which were similar to the trends of enzyme activities. Compared with the control, 0.15 g L−1 of Ca ascorbate and CaCl2 increased the activity of succinate dehydrogenase in P. kudriavzevii, thereby enhancing the utilization of nutrients by yeast cells, and calcium ascorbate had the strongest effect. The expressions of HXT5, ADH6, PET100p, and Pga62 were significantly higher in the Ca ascorbate treatment than the other groups, and the CaCl2 treatment was also significantly higher than the control. These results indicated that Ca ascorbate can effectively improve the energy metabolism and cell wall synthesis and slow down the senescence of yeast cells. In general, Ca ascorbate can improve the environmental adaptability of P. kudriavzevii and thus improve the biocontrol effect, which is associated with inducing antioxidant enzymes in yeast cells and enhancing energy metabolism and nutrient utilization efficiency to increase nutrient competition with pathogens.IMPORTANCE Antagonistic yeast is a promising way to control postharvest fruit decay because of its safety and broad-spectrum resistance. However, the biocontrol efficacy of yeast is limited by environmental stress, such as oxidative stress. Therefore, the improvement of antioxidant capacity has become a research hot spot in improving the biocontrol efficacy of yeast. The induction of Ca ascorbate on the antioxidant capacity and physiological activity of yeast was studied. The results showed better induction of antioxidant enzyme and physiological activity in yeast by Ca ascorbate for better antioxidant capacity, and Ca2+ also played a synergistic promotion effect, which improved the biocontrol efficacy. These results provide an approach for the research and application of improving the environmental adaptability and biocontrol effectiveness of yeast.

Alternative methods for angular stain control in mangoes (Mangifera indica L.)

The conventional methods used for angular stain control are generally chemical methods, however the use of these products can cause high environmental impact and damage to consumer health if it is used in large quantities and undiluted and applied correctly. Based on this problem, this work aimed to evaluate in vitro alternative forms of control using Saccharomyces yeast (with probiotic potential), ethanolic extracts of Mauritia flexuosa (Buriti) and Miconia albicans (Cinnamon-old) plants. To evaluate four GRAS substances in angular leaf spot control caused by Xanthomonas campestris pv. Mangifera indica, during the postharvest period in mangoes. In vitro results using antagonist yeasts showed no inhibitory effect against X. campestris. However, the extracts of the plants Miconia albicans and Mauritia flexuosa showed a significant inhibition. Thus, as two GRAS substances, 1%, 1.5% and 3% sodium carbonate and 3% sodium bicarbonate inhibited X. campestris growth 100%. Given the results obtained, the plant extracts and the GRAS substances tested were effective in controlling phytobacteria and proved to be an alternative in controlling angular leaf spot, thus avoiding economic losses during the mango postharvest phase.

Insight into Yeast–Mycotoxin Relations

Fungal mycotoxins are secondary metabolites that can be present in green forage, hay, or silage. Consumption of contaminated plants or agricultural products can cause various animal and human diseases, which is why problems associated with mycotoxins have received particular attention. In addition, public pressure to produce healthy food and feed is also increasing. As the results of several surveys indicate that yeasts can decrease toxic effects by binding or converting secondary metabolites or control growth of harmful fungi, this article provides an overview of the yeast species that can have great potential in detoxification. The most important antagonistic yeast species against toxigenic fungi are described and the mode of their inhibitory mechanisms is also discussed. We provide an insight into toxin binding and biotransformation capacities of yeasts and examples of their use in silo. Issues requiring further study are also mentioned.

Isolation and Identification of Wild Yeast from Malaysian Grapevine and Evaluation of Their Potential Antimicrobial Activity against Grapevine Fungal Pathogens.

Pathogenic fungi belonging to the genera Botrytis, Phaeomoniella, Fusarium, Alternaria and Aspergillus are responsible for vines diseases that affect the growth, grapevine yield and organoleptic quality. Among innovative strategies for in-field plant disease control, one of the most promising is represented by biocontrol agents, including wild epiphytic yeast strains of grapevine berries. Twenty wild yeast, isolated and molecularly identified from three different Malaysian regions (Perlis, Perak and Pahang), were evaluated in a preliminary screening test on agar to select isolates with inhibition against Botrytis cinerea. On the basis of the results, nine yeasts belonging to genera Hanseniaspora, Starmerella, Metschnikowia, Candida were selected and then tested against five grape berry pathogens: Aspergillus carbonarius, Aspergillus ochraceus, Fusarium oxysporum, Alternaria alternata and Phaeomoniella chlamydospora. Starmerella bacillaris FE08.05 and Metschnikowia pulcherrima GP8 and Hanseniaspora uvarum GM19 showed the highest effect on inhibiting mycelial growth, which ranged between 15.1 and 4.3 mm for the inhibition ring. The quantitative analysis of the volatile organic compound profiles highlighted the presence of isoamyl and phenylethyl alcohols and an overall higher presence of low-chain fatty acids and volatile ethyl esters. The results of this study suggest that antagonist yeasts, potentially effective for the biological control of pathogenic moulds, can be found among the epiphytic microbiota associated with grape berries.

Fungicide tolerance of antagonists in the management of mango anthracnose caused by <i>Colletotrichum gloeosporoides</i>

In the present study, fungicide tolerance of antagonists (yeast and Lactobacillus) with two fungicides viz., Mancozeb and Ridomil gold were conducted using turbidometric method. Findings of study revealed that, ridomil and mancozeb treatments could inhibit the growth of yeasts and Lactobacillus to some extent but did not completely inhibit. In this study, it was found that potential yeast and Lactobacillus antagonists were tolerant to both mancozeb and ridomil fungicides up to 2000 ppm concentrations. This result implies that the antagonistic yeast and Lactobacillus isolates were not adversely affected by both mancozeb and ridomil fungicides. So, these isolates can form an important component of Integrated disease management of mango anthracnose.

A Sustainable Alternative for Postharvest Disease Management and Phytopathogens Biocontrol in Fruit: Antagonistic Yeasts

Postharvest diseases of fruits caused by phytopathogens cause losses up to 50% of global production. Phytopathogens control is performed with synthetic fungicides, but the application causes environmental contamination problems and human and animal health in addition to generating resistance. Yeasts are antagonist microorganisms that have been used in the last years as biocontrol agents and in sustainable postharvest disease management in fruits. Yeast application for biocontrol of phytopathogens has been an effective action worldwide. This review explores the sustainable use of yeasts in each continent, the main antagonistic mechanisms towards phytopathogens, their relationship with OMIC sciences, and patents at the world level that involve yeast-based-products for their biocontrol.

Phenylethanol as a quorum sensing molecule to promote biofilm formation of the antagonistic yeast Debaryomyces nepalensis for the control of black spot rot on jujube

Microbial biocontrol agents have become an effective way to inhibit post-harvest diseases of fruits and vegetables, where antagonistic yeast with antimicrobial properties are often employed. In this study, Debaryomyces nepalensis, isolated from the leaves of jujube and identified with internal transcribed spacer sequences, can effectively control the post-harvest black spot of jujube caused by Alternaria alternate, even though it showed no direct inhibitory effects on A. alternate. Phenylethanol, as a quorum sensing molecule, was identified by HPLC to be one of the major metabolites during the culture of D. nepalensis. Phenylethanol could promote the biofilm formation ability of D. nepalensis and increase its adhesion to the surface of jujube fruit, and the control effect of 2 mmol L−1 phenylethanol combined with D. nepalensis on jujube fruit black spot was increased by 15 % compared with D. nepalensis alone. In conclusion, the results of this work provided a new perspective for improving the biological control efficiency of D. nepalensis.

Effectiveness of fungal, bacterial and yeast antagonists for management of mango anthracnose (Colletotrichum gloeosporioides)

BackgroundMango anthracnose, caused by Colletotrichum gloeosporioides, is one of the most important diseases of mango crop. It mainly attacks leaves, flowers, young fruits and twigs and also appears as a post-harvest disease of ripened fruits. Application of bio-control agents has huge potential in plant disease management. The goal of the present research was to establish the potential of individual and combined bio-control agents for the management of mango anthracnose under in vitro and under field conditions.ResultsThe antagonistic reaction of six fungi, six bacteria and nine yeasts against C. gloeosporioides on potato dextrose agar medium and malt extract agar medium was observed among which Trichoderma harzianum was found to be the most efficient with 89.26% mycelial growth inhibition. Evaluation of bio-control agents against anthracnose disease development on mango fruit revealed that dip treatment of mango fruits in spore suspension (1.2 × 104 cfu/ml) of T. harzianum for 5 min was the most effective and provided disease control to the tune of 81.67%. Combined application of effective bio-control agents as a post-harvest fruit dip treatment was also evaluated against the mango anthracnose on mango fruits, where the treatment of T. harzianum + Pichia anomala was very effective with 93.39% disease control. Under field conditions, three consecutive sprays of T. harzianum, starting with the initiation of disease on leaves, followed by other two sprays at an interval of 15 days during 2015 and 2016 were found the best for the management of mango anthracnose disease both on leaves and on fruits at two locations.ConclusionsThe combined and individual applications of bio-control agents, viz.T. harzianum, Bacillus subtilis and P. anomala, through foliar spray or by fruit dip had the potential to control mango anthracnose. The bio-formulations of these bio-control agents had the potential to replace chemical fungicides and also protect the natural environment, thus playing a significant role in integrated disease management.