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

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.

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.

Suppression of Bacterial Leaf Spot by Green Synthesized Silica Nanoparticles and Antagonistic Yeast Improves Growth, Productivity and Quality of Sweet Pepper

Plants are challenged with many kinds of biotic stresses caused by different living organisms, which result in various types of diseases, infections, and damage to crop plants and ultimately affect crop productivity. Plant disease management strategies based on current approaches are necessary for sustainable agriculture. A pot experiment was carried out under greenhouse conditions to evaluate the potential of green synthesized silica nanoparticles (SiO2-NPs) and antagonistic yeast (Saccharomyces cerevisiae) against pepper bacterial leaf spot disease, caused by Xanthomonas vesicatoria. In addition, to assess their efficacy and suppressive effects in reducing disease severity and improving sweet pepper growth, productivity, and quality. Results revealed that the combination of BCA (5%) and SiO2-NPs (150 ppm) was the most effective treatment for reducing disease severity and improving vegetative growth characters, mineral contents (N, P, K, Ca, Mg, and Si in leaves), as well as stimulating polyphenol oxidase (PPO) activity of sweet pepper leaves at 90 days from transplanting, while also at harvesting time enhancing sweet pepper fruit yield quality parameters significantly. In conclusion, green synthesized silica nanoparticles combined with antagonistic yeast have the potential to suppress a bacterial leaf spot disease with ecologically-sound management, while also boosting sweet pepper growth, productivity, and quality.

Selecting Antagonistic Yeast for Postharvest Biocontrol of Colletotrichum gloeosporioides in Papaya Fruit and Possible Mechanisms Involved

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.

Control of Penicillium glabrum by Indigenous Antagonistic Yeast from Vineyards

Biocontrol is one of the most promising alternatives to synthetic fungicides for food preservation. Botrytis cinerea, Alternaria alternata, and Aspergillus section Nigri are the most concerning pathogens for grape development. However, frequently, other species, such as Penicillium glabrum in this study, are predominant in spoiled bunches. In this work, 54 native yeasts from vineyards were screened by direct confrontation in potato dextrose agar plates as antagonists against P. glabrum. Isolates of Pichia terricola, Aureobasidium pullulans, and Zygoascus meyerae were selected for their antagonist activity in vitro, plus isolates of Pichia kudriavzevii, Hormonema viticola, and Hanseniaspora uvarum were used as negative controls. However, in vivo, confrontations in wounded grapes showed disagreement with direct confrontation in vitro. P. terricola, P. kudriavzevii, H. viticola, Z. meyerae, and H. uvarum significantly reduced the incidence of P. glabrum on grapes. Nevertheless, P. terricola, H. viticola, and H. uvarum themselves spoiled the wounded grapes. Inhibitions were associated with different mechanisms such as the production of volatile organic compounds (VOCs), lytic enzymes, biofilm formation, and competition for nutrients. The isolates of P. kudriavzevii L18 (a producer of antifungal VOCs which completely inhibited the incidence of P. glabrum) and Z. meyerae L29 (with pectinase, chitinase and β-glucanase activity and biofilm formation which reduced 70% of the incidence of P. glabrum) are proposed as suitable biocontrol agents against P. glabrum.

Production of Bio-Fungicide from Sugarcane Bagasse using Pichia membranifaciens Yeast and its Activity Against Post-Harvest Pathogenic Fungi

Antagonistic yeast Pichia membranifaciens can produce killer toxins and hydrolytic enzymes to degrade pathogenic fungi cell walls. In this study, sugarcane bagasse was hydrolyzed and used as a low-cost carbon source to produce bio-fungicide using P. membranifaciens. In a growth medium obtained from bagasse hydrolysis containing 25 g/l sugar, with optimized amounts of nitrogen sources (2% (w/v)), NaCl and K2HPO4 (0.5% (w/v)) and in the presence of hydrophilic surfactant, Triton X100 (0.02% (w/v)), the yeast was able to produce 3782 mg/l bio-fungicide. The activity and toxicity of the produced bio-fungicide were tested against some post-harvest pathogenic fungi, including Aspergillus niger, Penicillium digitatum, and Phytophthora capsici. Minimum biocidal concentration (MBC) and minimum inhibitory concentration (MIC) were determined to be 378.2 and 37.82 mg/l, respectively. According to the results, the produced bio-fungicide has the potential for preserving agricultural products in the warehouse.

Antagonistic Yeasts: A Promising Alternative to Chemical Fungicides for Controlling Postharvest Decay of Fruit

Fruit plays an important role in human diet. Whereas, fungal pathogens cause huge losses of fruit during storage and transportation, abuse of chemical fungicides leads to serious environmental pollution and endangers human health. Antagonistic yeasts (also known as biocontrol yeasts) are promising substitutes for chemical fungicides in the control of postharvest decay owing to their widespread distribution, antagonistic ability, environmentally friendly nature, and safety for humans. Over the past few decades, the biocontrol mechanisms of antagonistic yeasts have been extensively studied, such as nutrition and space competition, mycoparasitism, and induction of host resistance. Moreover, combination of antagonistic yeasts with other agents or treatments were developed to improve the biocontrol efficacy. Several antagonistic yeasts are used commercially. In this review, the application of antagonistic yeasts for postharvest decay control is summarized, including the antagonistic yeast species and sources, antagonistic mechanisms, commercial applications, and efficacy improvement. Issues requiring further study are also discussed.