Microbial biological control of Botrytis bunch rot (Botrytis cinerea) of grapevine (Vitis vinifera) crops: A meta-analysis

The escalating impacts of climate change are exacerbating the spread and intensity of Botrytis bunch rot (BBR), a devastating grapevine disease caused by the necrotrophic fungus Botrytis cinerea. Growers have traditionally relied on synthetic fungicides to manage BBR, but the increasing resistance of B. cinerea to these chemicals, coupled with growing environmental concerns, has intensified the search for more sustainable and eco-friendly control strategies. Microbial biological control agents (MBCAs) have emerged as a promising alternative for BBR management. This review explores research on using MBCAs to control BBR in grapevine fields. Various microorganisms have shown efficacy, including bacteria such as Bacillus subtilis, B. amyloliquefaciens, B. ginsengihumi, Pantoea agglomerans or Pseudomonas fluorescens, yeasts such as Saccharomyces cerevisiae, Metschnikowia fructicola or Candida sake, and filamentous fungi such as Trichoderma asperellum, T. pseudokoningii, Fusarium solani or Ulocladium atrum. These MBCAs employ diverse mechanisms of action, including direct antagonism through competition for space and nutrients, the production of lytic enzymes that degrade fungal cell walls, and the induction of plant defense mechanisms at both local and systemic levels. However, the effectiveness of these MBCAs can be influenced by environmental factors, with high temperatures and low humidity generally favoring their activity. Further research is needed to optimize MBCA application methods, elucidate the complex interactions between MBCAs, the pathogen, and the grapevine host, and explore the potential of combining multiple MBCAs for enhanced disease control. Integrating MBCAs with other sustainable practices offers a more holistic approach to BBR management, paving the way for a more environmentally friendly and effective strategy to combat this devastating disease.