Innovation in post-harvest biocontrol: novel strategies against <i>Botrytis cinerea</i> for grape preservation

Driven by the growing demand for sustainable agriculture, biocontrol is emerging as a key alternative to chemical fungicides in crop protection. This approach relies on living microorganisms, their metabolites, or other natural compounds to combat plant diseases and preserve food quality. In vitiviniculture, Botrytis cinerea poses a major challenge, particularly during grape storage, as it compromises fruit integrity. Although chemical fungicides are commonly used, their application is restricted in pre-harvest stages to avoid residues in the final product, prompting interest in natural solutions such as biocontrol. However, the number of microorganisms registered as active substances in the European Union remains limited, underscoring the need for improved selection and application strategies. This study aims to evaluate the performance of novel microbial isolates—specifically grapevine wood endophytes—as bioprotective agents, comparing them with commercial strains of Metschnikowia pulcherrima and Aureobasidium pullulans. The focus is on post-harvest application, particularly the storage phase, which is critical for maintaining grape quality. Selected bacterial isolates, primarily Actinobacteria, were tested on grape bunches previously infected with B. cinerea under controlled laboratory conditions. These trials assessed the microorganisms’ ability to colonise grape surfaces and remain viable during storage—key traits for effective biocontrol. Monitoring of disease incidence and severity revealed a significant reduction in B. cinerea growth on treated grapes. Further trials were conducted under industrial conditions in withering warehouses used for passito wine production. Experiments at two wineries tested the efficacy of the isolates, both individually and in microbial consortia, with and without adhesives to enhance treatment adherence. Results were particularly promising in environments with high Botrytis pressure, demonstrating biocontrol efficacy comparable to commercial agents. To our knowledge, this is the first study to investigate the use of novel endophytic microorganisms for biocontrol during the critical post-harvest grape drying phase, offering a promising alternative to chemical treatments.