Harnessing microbial consortia for induced systemic resistance and sustainable management of dry root rot in cluster bean under hot arid climatic conditions

Dry root rot, caused by <i>Macrophomina phaseolina</i>, severely threatens cluster bean production, necessitating sustainable management strategies. This study aimed to screen, characterize and evaluate microbial isolates with antagonistic potential against <i>M. phaseolina</i>. Among 763 isolates, <i>Trichoderma breve</i> 37F, <i>Pseudomonas</i> sp. 8B, <i>Aneurinibacillus aneurinilyticus</i> 16B, and <i>Bacillus velezensis</i> 32B exhibited strong biocontrol and plant growth-promoting traits. All four biocontrol agents demonstrated good compatibility. Pot experiments revealed that the four-microbe consortium comprising <i>T. breve</i> 37F + <i>Pseudomonas</i> sp. 8B + <i>A. aneurinilyticus</i> 16B + <i>B. velezensis</i> 32B significantly suppressed <i>M. phaseolina</i>, achieving 87.13% disease control and declining the percent disease incidence (PDI) to 16.7%. This consortium also enhanced plant growth, increasing plant height (1.66-fold), fresh weight (2.81-fold), dry weight (2.56-fold) and yield (21.4-fold) over the infected control. Significant improvements were observed in plant physiological and biochemical attributes, including increased total chlorophyll (3.16-fold), carotenoids (1.95-fold), total phenols (2.11-fold), flavonoids (2.53-fold), antioxidant activity (3.21-fold) and tannins (4.72-fold), alongside a 46.8% reduction in electrolyte leakage. Antioxidant enzyme activities, including peroxidase (4.05-fold), polyphenol oxidase (2.69-fold), phenylalanine ammonia lyase (1.93-fold), tyrosine ammonia lyase (2.01-fold), superoxide dismutase (2.94-fold) and catalase (2.25-fold), were significantly upregulated in consortium-treated plants. Field validation confirmed the efficacy of the four-microbe consortium, reducing PDI to 40.0% (42.0% disease control) while enhancing seed yield by 2.79-fold and 1.67-fold over the infected and mock controls, respectively. These findings demonstrate the potential of a microbial consortium as an eco-friendly biocontrol strategy. Future work should focus on formulation and large-scale field validation.