Discovery and comprehensive evaluation of new strategies for the postharvest biocontrol of anthracnose in avocado

Abstract

Anthracnose, caused mainly by Colletotrichum spp, is the leading postharvest disease affecting avocado (Persea americana), contributing to significant losses in global production. As concerns grow over the environmental impact and diminishing efficacy of synthetic fungicides, this study aimed to identify and evaluate microbial antagonists as sustainable biocontrol alternatives. Microorganisms were isolated from two primary sources: extreme environments in Cuatro Ciénegas, known for their oligotrophic and selective conditions; and various niches of the avocado ecosystem, including rhizosphere, carposphere, bark, and nectar. A total of 30 actinobacteria, 78 filamentous fungi, and other 13 bacterial isolates were screened in vitro against Colletotrichum spp., with promising candidates further evaluated through in vivo inhibition assays. Among the strains tested, Kosakonia cowanii VG1, isolated from the avocado carposphere, exhibited strong antifungal activity across assays. Genome analysis revealed biosynthetic gene clusters encoding siderophores and azole-containing RiPPs, which may underlie its inhibitory effects. The techno-economic evaluation showed a competitive production cost of $0.11 per dose, highlighting its scalability potential. Actinobacterial isolate Streptomyces nanshensis CC402A also demonstrated an effective in vitro and in vivo inhibition, with a low MIC and MFC of the crude extract. This isolate presents gene clusters for known antifungal metabolites, including valinomycin and HSAF-like compounds. This work supports the integration of prospecting in environments with strong ecological selective pressures, genomic mining, and economic modeling to discover and validate new microbial biocontrol agents.