Endophytic Bacillus velezensis BDKishJoy 6B promotes rice growth and enhances resistance to Magnaporthe oryzae

Rice blast, caused by Magnaporthe oryzae, is a persistent threat to rice production in Bangladesh, particularly in the haor (wet-land basin) region, where up to 80% yield loss occurs annually. This study aimed to explore the potential of an endophytic bacterium, Bacillus velezensis BDKishJoy-6B, for promoting growth and enhancing blast tolerance in rice cultivars commonly grown in this vulnerable agro-ecosystem. Fifteen isolates of P. oryzae were collected from haor regions and characterized morphologically and for pathogenicity. The most virulent isolate, KSH01 (GenBank: PQ269871.1), was selected for pathogenicity assays. Antagonistic endophytic bacteria were isolated from rice roots and screened for plant growth-promoting traits. The most effective isolate, BDKishJoy-6B, was identified as B. velezensis (GenBank accession: PQ770697.1). This strain was applied to two rice cultivars (US-2 and BRRI Dhan34) via seed priming, seedling priming, and combined treatments. Growth parameters, yield traits, defense gene expression (OsPOD, OsPAL1, OsPR5), and antioxidant enzyme activities (SOD, POD, APX, PPO, MDA) were assessed under artificial disease pressure. B. velezensis BDKishJoy-6B significantly enhanced rice growth and yield under blast stress, especially in BRRI Dhan34. Notably, seedling priming showed the highest upregulation of defense genes and antioxidant activities, correlating with reduced disease symptoms and increased biomass accumulation. Seedling priming with B. velezensis BDKishJoy-6B offers a promising bio-management strategy for controlling rice blast by modulating host antioxidant and defense pathways, with potential application in haor-based rice production systems.