Native beauveria bassiana isolates: harnessing endophytic capabilities for controlling fall armyworm infestation in maize

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ABSTRACT This study investigates the establishment and colonization dynamics of Beauveria bassiana as an endophyte in maize plants using various inoculation methods. Surface sterilization and fungal isolation confirmed B. bassiana as an endophyte, with isolates ChBb and NaBb exhibiting distinct colonization patterns. Notably, foliar spray demonstrated the highest initial colonization efficiency, with ChBb achieving 93.3% in leaves at 7 days post-inoculation (DPI), decreasing to 13.3% at 35 DPI. NaBb similarly exhibited high initial colonization via foliar spray, with 93.3% in leaves at 7 DPI, declining to 33.3% at 35 DPI. Molecular analysis using nested PCR confirmed the presence of B. bassiana DNA exclusively in treated tissues, with a consistent 300 bp PCR product observed in leaf, stem, and root samples. Phylogenetic analysis highlighted genetic relationships among B. bassiana isolates, underscoring their diversity and potential for biocontrol applications. Pathogenicity tests against Spodoptera frugiperda demonstrated significant mortality rates: ChBb achieved 77.20% mortality in direct contact assays (where larvae were exposed directly to the fungal spores) and 56.82% mortality in vivo (where larvae were fed plants colonized by the fungus), while NaBb resulted in 75.86% and 51.42% mortality, respectively. These findings emphasize the efficacy of B. bassiana as a biocontrol agent, particularly through foliar application for initial colonization in maize plants.