Isolation and Identification of Pathogens Associated with Fruit Rot of Tamarindusindica L. and Screening for Their Biocontrol Agents

Tamarindus indica L., a key economic tree species in tropical regions, suffers severely from postharvest decay. From 2023 to 2025, disease fruits exhibiting pericarp softening, pulp browning, and sticky exudates were collected in Yunnan, China. Pathogenicity tests following Koch’s postulates, combined with morphological characterization and phylogenetic analyses of the internal transcribed spacer (ITS), translation elongation factor 1-alpha (TEF 1α), and beta-tubulin (TUB) gene regions, identified the causal pathogen as Botryosphaeria fabicerciana (isolates ZWML-06, ZWML-44, ZWML-17). This is the first report of this postharvest disease on tamarind in Yunnan, filling an etiological gap. Additionally, an endophytic bacterium, designated BV-1, was isolated from asymptomatic pulp tissues. Whole-genome sequencing and phylogenetic analysis identified it as Bacillus velezensis. Strain BV-1 exhibited strong in vitro antagonistic activity against the pathogen, indicating promising biocontrol potential. Functional annotation revealed that BV-1 possesses a complex genetic system with developed transporter systems; its core metabolic network is dominated by nitrogen metabolism and redox processes, suggesting a potential “multi-target” antimicrobial mechanism. This study provides a theoretical basis and novel resources for the green control of postharvest diseases in tamarind.