Biocontrol of Non-Saccharomyces Yeasts in Vineyard against the Gray Mold Disease Agent Botrytis cinerea

Enhancing Botrytis disease management in tomato plants: insights from a Pseudomonas putida strain with biocontrol activity

AIMS

This study explores the biocontrol potential of Pseudomonas putida Z13 against Botrytis cinerea in tomato plants, addressing challenges posed by the pathogen's fungicide resistance. The aims of the study were to investigate the in vitro and in silico biocontrol traits of Z13, identify its plant-colonizing efficacy, evaluate the efficacy of different application strategies against B. cinerea in planta, and assess the capacity of Z13 to trigger induced systemic resistance (ISR) in plants.

METHODS AND RESULTS

The in vitro experiments revealed that Z13 inhibits the growth of B. cinerea, produces siderophores, and exhibits swimming and swarming activity. Additionally, the Z13 genome harbors genes that encode compounds triggering ISR, such as pyoverdine and pyrroloquinoline quinone. The in planta experiments demonstrated Z13's efficacy in effectively colonizing the rhizosphere and leaves of tomato plants. Therefore, three application strategies of Z13 were evaluated against B. cinerea: root drenching, foliar spray, and the combination of root drenching and foliar spray. It was demonstrated that the most effective treatment of Z13 against B. cinerea was the combination of root drenching and foliar spray. Transcriptomic analysis showed that Z13 upregulates the expression of the plant defense-related genes PR1 and PIN2 upon B. cinerea inoculation.

CONCLUSION

The results of the study demonstrated that Z13 possesses significant biocontrol traits, such as the production of siderophores, resulting in significant plant protection against B. cinerea when applied as a single treatment to the rhizosphere or in combination with leaf spraying. Additionally, it was shown that Z13 root colonization primes plant defenses against the pathogen.

Biocontrol strategies against Botrytis cinerea in viticulture: evaluating the efficacy and mode of action of selected winemaking yeast strains

Botrytis cinerea poses a recurring threat to viticulture, causing significant yield losses each year. The study explored the biocontrol capabilities of commercially used winemaking yeasts as a strategy to manage B. cinerea in grape berries. The winemaking yeast strains-Saccharomyces cerevisiae ES181, Saccharomyces pastorianus KBG6, S. cerevisiae BCS103, Lachancea thermotolerans Omega, and Torulaspora delbrueckii TD291-reduced B. cinerea growth and conidiation in vitro. Furthermore, they demonstrated a decreased disease severity and number of conidia in grape berries. Among these strains, S. cerevisiae BCS103 was the most effective, inducing the expression of the defense-related gene PR4 in berries. Its diffusible compounds and volatile organic compounds also reduced the expression of BcLTF2, a positive regulator of B. cinerea conidiogenesis. The examined winemaking yeast strains, especially S. cerevisiae BCS103, demonstrated effective inhibition of B. cinerea in vitro and in grape berries, influencing key defense genes and reducing BcLTF2 expression, offering potential solutions for disease management in viticulture. The study underscores the promise of commercially available winemaking yeast strains as eco-friendly tools against B. cinerea in viticulture. Leveraging their safety and existing use in winemaking offers a potential avenue for sustainable disease management.

Microbial Biofungicides as a Substitute for Chemical Fungicides in the Control of Phytopathogens: Current Perspectives and Research Directions

These days, two important issues are causing concern in the global community: the alarmingly growing trend of the human population and the issue of food security. To this end, people around the world have been searching for solutions that could feed the needy in a sustainable way. In response to this urgent call, scientists from around the world started working on increasing crop production and productivity by controlling crop pathogens that could harm the productivity of crops. Synthetic fungicides have been in use for controlling crop diseases for several decades, but later, due to the evidenced side effects of the fungicides, there have been attempts to shift towards a less cost-effective and eco-friendly method of controlling crop diseases, and so far, many remarkable results have been achieved. However, due to the less effective and shorter shelf life of microbial biofungicides, as well as the less accessibility of these microbial biofungicides to growers around the world, it became difficult to remove the fungicides totally from the market. To minimize this problem, researchers suggested an integrated approach: the combination of microbial biofungicides with a reduced dose of synthetic fungicides. Hence, this review explored the status as well as the merits and demerits of microbial biofungicides as compared to synthetic fungicides.

On the Way to the Technological Development of Newly Selected Non-Saccharomyces Yeasts Selected as Innovative Biocontrol Agents in Table Grapes

Post-harvest decay of fresh table grapes causes considerable annual production losses. The main fungal agents of decay both in pre- and post-harvest are B. cinerea, Penicillium spp., Aspergillus spp., Alternaria spp., and Cladosporium spp. To date, the use of agrochemicals and SO2 are the main methods to control grape molds in pre- and postharvest, respectively. Significant improvements, however, have already been made in to apply innovative and more environmentally sustainable control strategies, such as Biological Control Agents (BCAs), which can reduce disease severity in both pre- and post-harvest. In this study, 31 new non-Saccharomyces yeast strains, isolated from berries of native Apulian table grape genotypes, were tested for their in vivo effectiveness against grey mold of table grapes, resulting in two St. bacillaris ('N22_I1' and 'S13_I3'), one S. diversa ('N22_I3'), one A. pullulans ('OLB_9.1_VL') and one H. uvarum ('OLB_9.1_BR') yeast strains that were marked as efficient and good BCAs. Their mechanisms of action were characterized through in vitro assays, and additional characteristics were evaluated to assess the economic feasibility and viability for future technological employment. Their effectiveness was tested by reducing the working concentration, their antagonistic effect on a wide range of fungal pathogens, their ability to survive in formulations with long shelf life, and their safety to human health.

From bioprotective effects to diversification of wine aroma: Expanding the knowledge on Metschnikowia pulcherrima oenological potential

Microbial diseases are of major concern in vitiviniculture as they cause grape losses and wine alterations, but the prevention with chemical substances represents a risk to human health and agricultural ecosystem. A promising alternative is the biocontrol and bioprotection activity of non-Saccharomyces yeasts, such as Metschnikowia pulcherrima, which also presents positive oenological traits when used in multistarter fermentations. The aim of this study was to assess the impact of a selected M. pulcherrima strain in the post-harvest withering and vinification of Garganega grapes to produce the sweet 'passito' wine Recioto di Gambellara DOCG (Italy). M. pulcherrima was firstly inoculated on grape at the beginning of the withering process, and afterwards in must for multistarter sequential microfermentation trials with Saccharomyces cerevisiae. Microbiological, chemical, and sensory analyses were carried out to monitor the vinification of treated and control grapes. Grape bunches during withering were a suitable environment for the colonization by M. pulcherrima, which effectively prevented growth of molds. Differences in grape must composition were observed, and the diverse inoculation strategies caused noticeable variations of fermentation kinetics, main oenological parameters, wine aroma profile, and sensory perception. M. pulcherrima proved effective to protect grapes against fungal infections during withering and contribute to alcoholic fermentation generating wine with distinguished aromatic characteristics.

Biocontrol Efficacy of Metschnikowia spp. Yeasts in Organic Vineyards against Major Airborne Diseases of Table Grapes in the Field and in Postharvest

The aim of this work was to evaluate the efficacy of two antagonistic yeasts, Metschnikowia pulcherrima strain MPR3 and M. fructicola strain NRRL Y-27328 (commercial product NOLI), applied in addition to the "on-farm biological treatments" (BIO) carried out during the production season, for the containment of powdery mildew and grey mould diseases on organic table grapes 'Italia'. The yeast strains were applied in the field three times, and their efficacy was evaluated during the production season and under postharvest conditions. Overall, M. pulcherrima MPR3 combined with BIO treatments reduced disease incidence caused by Erysiphe necator and disease incidence and severity caused by Botrytis cinerea with values between 67.8% and 86.2%, showing higher efficacy than BIO treatments applied alone and in combination with NOLI. Field treatments based on BIO+MPR3 maintained their performance also during fruit storage, protecting grape berries from grey mould development to a greater extent than the other treatments (disease reduction of about 98%). Thus, the presence of M. pulcherrima MPR3 seems to improve disease management both in the field and in postharvest environments, without negative impacts on grape microbial communities. These findings highlight the potential of M. pulcherrima MPR3 as a promising alternative strategy for disease control in organic vineyards and in postharvest, providing sustainable solutions to improve food quality and safety.

Bacillus velezensis FX-6 suppresses the infection of Botrytis cinerea and increases the biomass of tomato plants

Botrytis cinerea causing tomato gray mold is a major cause of economic loss in tomato production. It is urgent and necessary to seek an effective and environmentally friendly control strategy to control tomato grey mold disease. In this study, Bacillus velezensis FX-6 isolated from the rhizosphere of plants displayed significant inhibitory ability against B. cinerea and could promote tomato plant growth. FX-6 could effectively inhibit the growth of Botrytis cinerea mycelium in vitro and in vivo, and the inhibitory rate in vitro could reach 78.63%. According to morphological observations and phylogenetic trees based on sequences of the 16S rDNA and gyrA (DNA gyrase subunit A) genes, the strain FX-6 was identified as Bacillus velezensis. In addition, B. velezensis FX-6 showed antagonistic activity against seven phytopathogens, this indicated that FX-6 had broad-spectrum biocontrol activity. We also found that FX-6 fermentation broth had the strongest antagonistic activity against B. cinerea when the culture time was 72 hours, and the inhibition rate was 76.27%. The growth promotion test revealed that strain FX-6 significantly promoted tomato seed germination and seedling growth. Further deeply study on growth-promoting mechanism indicated that the FX-6 produced IAA and siderophore, and had ACC deaminase activity. The trait of significant biological control activity and growth promoting effect on tomato imply that B. velezensis FX-6 has the potential to be used as a biocontrol agent for tomato gray mold management.

Unlocking antagonistic potential of Bacillus amyloliquefaciens KRS005 to control gray mold

To establish a safe, efficient, and simple biocontrol measure for gray mold disease caused by Botrytis cinerea, the basic characteristics and antifungal activity of KRS005 were studied from multiple aspects including morphological observation, multilocus sequence analysis and typing (MLSA-MLST), physical-biochemical assays, broad-spectrum inhibitory activities, control efficiency of gray mold, and determination of plant immunity. The strain KRS005, identified as Bacillus amyloliquefaciens, demonstrated broad-spectrum inhibitory activities against various pathogenic fungi by dual confrontation culture assays, of which the inhibition rate of B. cinerea was up to 90.3%. Notably, through the evaluation of control efficiency, it was found that KRS005 fermentation broth could effectively control the occurrence of tobacco leaves gray mold by determining the lesion diameter and biomass of B. cinerea on tobacco leaves still had a high control effect after dilution of 100 folds. Meanwhile, KRS005 fermentation broth had no impact on the mesophyll tissue of tobacco leaves. Further studies showed that plant defense-related genes involved in reactive oxygen species (ROS), salicylic acid (SA), and jasmonic acid (JA)-related signal pathways were significantly upregulated when tobacco leaves were sprayed with KRS005 cell-free supernatant. In addition, KRS005 could inhibit cell membrane damage and increase the permeability of B. cinerea. Overall, KRS005, as a promising biocontrol agent, would likely serve as an alternative to chemical fungicides to control gray mold.

Biocontrol and Probiotic Function of Non-Saccharomyces Yeasts: New Insights in Agri-Food Industry

Fermented food matrices, including beverages, can be defined as the result of the activity of complex microbial ecosystems where different microorganisms interact according to different biotic and abiotic factors. Certainly, in industrial production, the technological processes aim to control the fermentation to place safe foods on the market. Therefore, if food safety is the essential prerogative, consumers are increasingly oriented towards a healthy and conscious diet driving the production and consequently the applied research towards natural processes. In this regard, the aim to guarantee the safety, quality and diversity of products should be reached limiting or avoiding the addition of antimicrobials or synthetic additives using the biological approach. In this paper, the recent re-evaluation of non-Saccharomyces yeasts (NSYs) has been reviewed in terms of bio-protectant and biocontrol activity with a particular focus on their antimicrobial power using different application modalities including biopackaging, probiotic features and promoting functional aspects. In this review, the authors underline the contribution of NSYs in the food production chain and their role in the technological and fermentative features for their practical and useful use as a biocontrol agent in food preparations.

Indigenous Yeasts for the Biocontrol of Botrytis cinerea on Table Grapes in Chile

One hundred twenty-five yeast strains isolated from table grapes and apples were evaluated for the control Botrytis cinerea of in vitro and in vivo. Ten strains were selected for their ability to inhibit mycelial growth of B. cinerea in vitro. In the in vivo assays, these yeasts were tested at 20 °C on 'Thompson Seedless' berries for 7 days; only three were selected (m11, me99 and ca80) because they significantly reduced the incidence of gray mold. These three yeast strains were then evaluated at different concentrations (1 × 10⁷, 1 × 10⁸ and 1 × 10⁹ cells mL^-1) on 'Thompson Seedless' grape berries at 20 °C. The strains m11, me99 and ca80 reduced the incidence of B. cinerea to 11.9, 26.1 and 32.1%, respectively, when the berries were submerged in a yeast suspension at a concentration of 1 × 10⁹ cells mL^-1 24 h before inoculation with B. cinerea. The most favorable pH for antifungal activity was 4.6 in the three isolates. The three yeast strains secreted the hydrolytic enzymes chitinase and β-1-glucanase, and two strains (me99 and ca80) produced siderophores. The three yeast strains exhibited low oxidative stress tolerance and only strain m11 had the ability to produce biofilms. The strains were identified using 5.8S-ITS rDNA PCR-RFLP and correspond to the Meyerozyma guilliermondii (m11) and Aureobasidium pullulans (me99 and ca80) species.

Starmerella bacillaris Released in Vineyards at Different Concentrations Influences Wine Glycerol Content Depending on the Vinification Protocols

Starmerella bacillaris is a non-Saccharomyces yeast proposed for must fermentation together with Saccharomyces cerevisiae because of its high glycerol and moderate volatile acidity production. Furthermore, it was demonstrated that the same S. bacillaris strains that possess interesting technological properties exhibited antifungal activity against Botrytis cinerea, suggesting the release of this yeast in the vineyard. To obtain a positive effect during the following winemaking process, the maintenance of suitable concentrations of S. bacillaris is essential. Therefore, to obtain information on the survival of S. bacillaris, a small-scale field trial was performed. One week before the harvest, two different concentrations of S. bacillaris (10⁶ and 10⁷ cells/mL) were sprayed on Pinot grigio bunches, and the strain concentration was monitored by means of qPCR during the subsequent fermentation process. In addition, the combined effect of different winemaking techniques was evaluated, i.e., the vinification of juice, juice with marc and cryomaceration treatment. Results demonstrated that, under the tested conditions, S. bacillaris released in the vineyard remained viable for one week on grape bunches and increased glycerol content during the subsequent fermentation process. Different vinification protocols influenced cell concentrations. In particular, the cryomaceration treatment, due to the use of low temperature, supported S. bacillaris growth due to its cryotolerant aptitude. The collected data open new perspectives on the control of alcoholic fermentation, involving both vineyard and cellar management.

A Review of Cultural Practices for Botrytis Bunch Rot Management in New Zealand Vineyards

Botrytis bunch rot of grapes (BBR) causes substantial crop and wine quality issues globally. Past and present foundations for BBR control are based upon synthetic fungicides and varying forms of canopy management. Many authors regard the continued dependence on fungicides as unsustainable and have urged greater deployment of cultural, biological and nutritional strategies. However, in contrast to organic wine production, the uptake of alternative strategies in conventional vineyards has been slow based on cost and perceived reliability issues. This review summarises research from many different wine growing regions in New Zealand with the aim of demonstrating how traditional and newly developed cultural control practices have cost-effectively reduced BBR. In addition to reviewing traditional cultural practices (e.g., leaf removal), mechanical tools are described that remove floral trash and mechanically shake the vines. Multi-omics has improved our knowledge of the underlying changes to grape berries after mechanical shaking. Exogenous applications of calcium may correct calcium deficiencies in the berry skin and reduce BBR but the outcome varies between cultivar and regions. Nitrogen aids in grapevine defence against BBR but remains a complex and difficult nutrient to manage. The sustainable growth of organics and The European Green Deal will stimulate researchers to evaluate new combinations of non-chemical BBR strategies in the next decade.

Antifungal activity of non-conventional yeasts against Botrytis cinerea and non-Botrytis grape bunch rot fungi

Grapes harbour a plethora of non-conventional yeast species. Over the past two decades, several of the species have been extensively characterised and their contribution to wine quality is better understood. Beyond fermentation, some of the species have been investigated for their potential as alternative biological tools to reduce grape and wine spoilage. However, such studies remain limited to a few genera. This work aimed to evaluate the antagonistic activity of grape must-derived non-conventional yeasts against Botrytis cinerea and non-Botrytis bunch-rotting moulds and to further elucidate mechanisms conferring antifungal activity. A total of 31 yeast strains representing 21 species were screened on different agar media using a dual culture technique and liquid mixed cultures, respectively. Pichia kudriavzevii was the most potent with a minimum inhibitory concentration of 10² cells/mL against B. cinerea but it had a narrow activity spectrum. Twelve of the yeast strains displayed broad antagonistic activity, inhibiting three strains of B. cinerea (B05. 10, IWBT FF1 and IWBT FF2), a strain of Aspergillus niger and Alternaria alternata. Production of chitinases and glucanases in the presence of B. cinerea was a common feature in most of the antagonists. Volatile and non-volatile compounds produced by antagonistic yeast strains in the presence of B. cinerea were analysed and identified using gas and liquid chromatography mass spectrometry, respectively. The volatile compounds identified belonged mainly to higher alcohols, esters, organosulfur compounds and monoterpenes while the non-volatile compounds were cyclic peptides and diketopiperazine. To our knowledge, this is the first report to demonstrate inhibitory effect of the non-volatile compounds produced by various yeast species.

The Microbiome of the ‘Williams’ Pear Variety Grown in the Organic Orchard and Antifungal Activity by the Autochthonous Bacterial and Yeast Isolates

The total diversity of bacterial and fungal communities associated with the phyllosphere (fruits and leaves) of the ‘Williams’ pear variety was analyzed in two phenological stages during fruit development and maturation. The antagonistic potential of autochthonous bacterial and yeast isolates against phytopathogenic fungi was also evaluated. A metabarcoding approach revealed Pantoea, Sphingomonas, Hymenobacter, Massilia, and Pseudomonas as dominant bacterial constituents of the pear phyllosphere, whilst most abundant among the fungal representatives identified were Metschnikowia, Filobasidium, Aureobasidiumpullulans, Botrytis cinerea, and Taphrina. The traditional culturable approach revealed that the Pseudomonas genus with P. graminis, P. putida, and P. congelans was most prevalent. The most frequently cultivated fungal representatives belonged to the genus Fusarium with six identified species. A broad range of the antagonistic activity was detected for the Hannaella luteola and Metschnikowia pulcherrima yeasts, significantly affecting the growth of many fungal isolates in the range of 53–70%. Fusarium sporotrichioides was the most susceptible fungal isolate. The autochthonous antagonistic yeasts H. luteola and M. pulcherrima might be powerful biological control agents of postharvest diseases caused by Fusarium spp. and common pathogens like Monilinia laxa, Botrytis cinerea, Alternaria tenuissima, and Cladosporium cladosporioides.