Biocontrol and ecophysiological characterization of bacterial and yeast BCA candidates isolated from two different environments to control postharvest diseases

Biocontrol agents are a sustainable alternative to chemical fungicides in postharvest protection. Part of their success depends on using strains able to persistently colonize the host and maintain a broad activity from the field to the storage facilities. In this report, we evaluated 213 potential biocontrol agents (124 bacteria, 78 yeasts, and 11 filamentous fungi) isolated from two contrasting environments, the Pyrenees Mountains and the Ebro Valley (Catalonia, Spain). Their efficacy was tested against the three main postharvest pathogens of apples: Penicillium expansum , Botrytis cinerea , and Rhizopus stolonifer . The results showed that 4 bacteria and 25 yeast strains were effective against these pathogens, reducing their incidence by more than 75 %. From these results, two Pantoea agglomerans and two Vishniacozyma carnescens were further studied in terms of growth at different temperatures and water availability in vitro and their persistence on apple surfaces. The ecophysiological characterization showed that the valley P. agglomerans strain tolerated lower water activities better than the mountain strain, suggesting adaptation to the region’s hot and dry climate. In contrast, the mountain V. carnescens performed better at low temperatures, while the valley strain showed superior growth at 30 ºC, consistent with their respective environmental origins. In conclusion, these results indicated the need to consider the environmental adaptability of potential biocontrol agents when searching for new BCA strains. • Culturomics increased effective microbial candidates, with 107 of 213 isolates reducing P. expansum incidence by >50 %. • 4 bacteria and 25 yeasts controlled P . expansum , B . cinerea , and R . stolonifer , reducing disease incidence by >75 %. • Valley Pantoea agglomerans tolerated lower water activities than the mountain strain, suggesting adaptation to hot, dry climates. • Mountain Vishniacozyma carnescens performed better at low temperatures, while the valley strain grew better at 30 ºC.