Native Vineyard Non-Saccharomyces Yeasts Used for Biological Control of Botrytis cinerea in Stored Table Grape

A Comparative Transcriptomic Study Reveals Temporal and Genotype-Specific Defense Responses to Botrytis cinerea in Grapevine

Grapevine (Vitis vinifera L.), a globally significant crop, is highly susceptible to Botrytis cinerea, the causative agent of gray mold disease. This study investigates transcriptomic responses to B. cinerea in tolerant and susceptible grapevine genotypes using RNA sequencing (RNA-seq). Differentially expressed genes (DEGs) were identified at three time points (T1, T2, T3), highlighting both genotype-independent and genotype-specific responses. Early-stage infection (T1) revealed rapid and robust activation of defense pathways in both genotypes, though the tolerant genotype showed enhanced modulation of metabolic processes by T2, prioritizing secondary metabolism and stress adaptation over growth. In contrast, the susceptible genotype exhibited less coordinated metabolic reprogramming, with delayed or weaker activation of key defense mechanisms. Gene Ontology and KEGG analyses identified critical pathways, including phenylpropanoid biosynthesis-like lignin metabolism, MAPK signaling, as well as candidate genes such as WRKY transcription factors and enzymes involved in cell wall fortification and antifungal compound biosynthesis. Genotype-specific responses emphasized metabolic flexibility as a determinant of resistance, with the tolerant genotype exhibiting superior resource allocation to defense pathways. These findings provide insights into the molecular basis of grapevine resistance to B. cinerea, offering potential targets for breeding or genetic engineering to enhance resilience and reduce fungicide dependency.

Botrytis fruit rot management: What have we achieved so far?

Botrytis cinerea is a destructive necrotrophic phytopathogen causing overwhelming diseases in more than 1400 plant species, especially fruit crops, resulting in significant economic losses worldwide. The pathogen causes rotting of fruits at both pre-harvest and postharvest stages. Aside from causing gray mold of the mature fruits, the fungus infects leaves, flowers, and seeds, which makes it a notorious phytopathogen. Worldwide, in the majority of fruit crops, B. cinerea causes gray mold. In order to effectively control this pathogen, extensive research has been conducted due to its wide host range and the huge economic losses it causes. It is advantageous to explore detection and diagnosis techniques of B. cinerea to provide the fundamental basis for mitigation strategies. Botrytis cinerea has been identified and quantified in fruit/plant samples at pre- and post-infection levels using various detection techniques including DNA markers, volatile organic compounds, qPCR, chip-digital PCR, and PCR-based nucleic acid sensors. In addition, cultural, physical, chemical, biological, and botanical methods have all been used to combat Botrytis fruit rot. This review discusses research progress made on estimating economic losses, detection and diagnosis, as well as management strategies, including cultural, physical, chemical, and biological studies on B. cinerea along with knowledge gaps and potential areas for future research.

Biocontrol of Alternaria alternata in cold-stored table grapes using psychrotrophic yeasts and bioactive compounds of natural sources

Alternaria alternata is a common fungal pathogen causing postharvest decay in table grapes. This study addressed the potential of autochthonous yeasts and bioactive compounds of natural sources to act as biocontrol agents (BCAs) against A. alternata in cold-stored table grapes. With this purpose, 19 yeast capable of growing at 0-1 °C were isolated from the surface of Red Globe table grapes. These isolates, along with the pre-isolated strain Metschnikowia pulcherrima RCM2, were evaluated as BCAs in wounded berries. From these results, six yeast isolates were pre-selected to be combined with bioactive compounds of natural sources, like phenolic compounds (PCs) of side streams of wine industry, including bunch stem extract (BSE) (5-25 %), and cane extract (CE) (5-25 %), and functional polysaccharides from shrimp waste such as chitosan (CH) (0.5 %). Then, the biocontrol efficacy of combined treatments beyond individual ones was compared. The results revealed that 4 yeast isolates, namely M. pulcherrima RCM2 and ULA146, and Aureobasidium pullulans FUL14 and FUL18, were the most effective. However, when combined with the natural bioactive compounds, their efficacy against A. alternata did not increase significantly. Notably, ULA146 and FUL18 demonstrated a biocontrol efficacy of 36-37 %, comparable to that of the treatment with commercial doses of SO2, which only showed a 27 % reduction in the lesion diameter. These findings highlight the potential of using psychrotrophic yeasts as BCAs against A. alternata in cold-stored table grapes. Combining these yeast strains with BSE, CE and CH did not increase BCAs efficacy against this pathogen at the concentrations tested. The development of effective biocontrol strategies for A. alternata could contribute to reducing reliance on chemically synthesized fungicides, promoting sustainable practices, aiming to improve the quality and safety of cold-stored table grapes.

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.

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.

Identification of antagonistic yeasts as potential biocontrol agents: Diverse criteria and strategies

Plant pathogenic and food spoilage microorganisms cause serious losses in crop production and severe damage during food manufacturing, transportation and storage. Synthetic antimicrobial agents are commonly used to control their propagation and harmful activities. However, the recent trend is shifting from chemicals towards safer and more eco-friendly alternatives. The use of antagonistic microorganisms as biological antimicrobial agents is becoming popular throughout the world to replace chemical agents. High numbers of microorganisms have turned out to exert adverse/inhibitory effects on other microorganisms including pathogens and spoiling strains. However, most of them are only active under laboratory conditions and their activity is sensitive to environmental changes. Only a small number of them can be used to manufacture biological protective products on an industrial scale. Therefore, there is a great need to identify additional antagonists. Yeasts have come to the forefront of attention because antimicrobial antagonism is fairly widespread among them. In the recent years, numerous excellent review articles covered various aspects of the phenomenon of antimicrobial antagonism of yeasts. However, none of them dealt with how antagonistic yeasts can be sought and identified, despite the high number and diverse efficiency of screening and identification procedures. As researchers working in different laboratories use different criteria and different experimental set-ups, a yeast strain found antagonistic in one laboratory may prove to be non-antagonistic in another laboratory. This review aims to provide a comprehensive and partially critical overview of the wide diversity of identification criteria and procedures to help researchers choose appropriate screening and identification strategies.

Ursolic acid, the main component of blueberry cuticular wax, inhibits Botrytis cinerea growth by damaging cell membrane integrity

Cuticular wax has been reported to play an essential role in resisting pathogens in various fruits. This study investigated the antifungal ability of the components in blueberry cuticular wax. We showed that the cuticular wax of blueberry inhibited the growth of Botrytis cinerea and ursolic acid (UA) was the key antifungal compound. UA inhibited B. cinerea growth in vitro and in vivo. Furthermore, UA increased extracellular conductivity and cellular leakage in B. cinerea, deformed the mycelial morphology, and destroyed cell ultrastructure. We also demonstrated that UA stimulated the accumulation of reactive oxygen species (ROS) and inactivated ROS scavenging enzymes. These results indicate that UA may exert antifungal effects against B. cinerea by disrupting cell membrane integrity. Thus, UA has significant potential as an agent for the control of gray mold in blueberry.

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.

Introduction to Special Issue: Plant Microbiome Augmentation and Stimulation-New Strategies to Grow Crops with Reduced Agrochemicals

Since the early work of Justus von Liebig on nutrient absorption in plants in the 1800s [...].