Bacillus velezensis JB23 suppresses pokkah boeng and other fungal diseases of sugarcane.

Pokkah boeng and other fungal diseases reduce sugarcane yield and stalk quality in many production regions. In this study, 190 bacterial isolates were obtained from sugarcane tissues and rhizosphere soil and screened for antagonistic activity against Fusarium sacchari. Strain JB23 showed strong inhibition against multiple sugarcane fungal pathogens and was identified as Bacillus velezensis based on colony morphology and multilocus sequence analysis. JB23 suppressed mycelial growth of Fusarium commune, Colletotrichum falcatum, Sporisorium scitamineum, and several additional fungal pathogens. Hyphae exposed to JB23 showed swelling, distortion, irregular branching, and collapse. Under greenhouse conditions, pretreatment with JB23 reduced pokkah boeng disease incidence from 80.33% to 19.45% and reduced disease index from 31.25 to 6.24. Similar reductions were observed under field conditions. JB23 treatment also increased antioxidant enzyme activities, reduced H₂O₂ and malondialdehyde accumulation, and altered phenylpropanoid- and PR-related defense responses, as indicated by PAL activity, ScPR1 expression, and lignin accumulation, while also increasing emergence rate, biomass accumulation, and SPAD values. Collectively, the results demonstrate that B. velezensis JB23 suppresses multiple fungal pathogens associated with sugarcane and reduces pokkah boeng severity under greenhouse and field conditions.