Functional characterisation of endophytic bacteria for biocontrol of charcoal rot (Macrophomina phaseolina) and plant growth promotion in common bean (Phaseolus vulgaris L)

: Macrophomina phaseolina, the causal agent of charcoal rot disease, poses a major threat to Phaseolus vulgaris production, particularly under climate change. Climate-induced environmental extremes, in which elevated temperatures and drought conditions favour disease development and pathogen aggressiveness, pose a major challenge to agricultural productivity globally. This study assessed the plant growth-promoting and biocontrol potential of six bacterial endophytic isolates against M. phaseolina in P. vulgaris , using an integration of biochemical, physiological antifungal, and seed germination assays. All the isolates show significant potential (p < 0.05) for producing ammonia and indole-3-acetic acid (IAA), solubilising nutrients, exhibiting hydrolytic enzyme activity, and demonstrating biocontrol traits. Of the six isolates, Serratia marcescens (PR1AI2) showed the highest IAA production and zinc solubilization activity, whereas Enterobacter sp. L1I9 showed enhanced phosphate solubilization. Protease activity was highest in PR1AI2, while Pseudomonas rhodesiae strain MSG-15 (L3I2) exhibited the strongest amylase activity. Dual culture assays demonstrated significant inhibition (p<0.05) of M. phaseolina mycelial growth and reduction in sporulation by the endophytic bacterial isolates. Among the isolates, L3I2 had the highest inhibition of mycelial growth (75.93%), whereas PR1AI2 qualitatively showed the greatest sporulation reduction. Seed germination assays further showed variable responses under M. phaseolina , with Streptomyces bikiniensis strain SBM (L2I3) and Enterobacter kobei strain V51 (PR5AI1) showing germination percentages of 80.00% and 75.56%, respectively, compared with 76.67% in the M. phaseolina -treated control. These isolates therefore represent promising candidates for sustainable biological management of charcoal rot disease in P. vulgaris, as they possess multiple traits associated with pathogen suppression and improved plant development