Harnessing microbial consortia to induce systemic resistance and modulate gene expression in cluster bean under...

Bacterial leaf blight (BLB) caused by Xanthomonas axonopodis pv. cyamopsidis (Xac), is a major constraint to cluster bean production, particularly under hot arid climatic conditions. This study aimed to develop effective microbial consortia for sustainable management of BLB. A total of 283 fungal and 480 bacterial isolates were screened in vitro for antagonistic activity against the pathogen. Four potent antagonists-Trichoderma afroharzianum (9 F), Aneurinibacillus aneurinilyticus (14B), Bacillus subtilis (26B) and Pseudomonas lalkuanensis (31B) were selected and showed good mutual compatibility. A pot experiment with 17 treatments was conducted to assess their individual and combined effects on disease suppression and plant growth promotion. Results revealed that four-microbe consortium (9 F + 14B + 26B + 31B) significantly reduced disease severity, lowering the PDI to 11.90% with 87.80% control compared to the infected control. This treatment also significantly improved plant growth, biomass, number of pods per plant and yield over the infected control. Field validation confirmed the efficacy of the consortium, showing a PDI reduction to 50.67% (48.88% disease control over infected control). This treatment resulted in a 44.90% increase in plant height, 73.30% increase in fresh weight, 86.70% increase in dry weight, 200.00% increase in the number of pods per plant and 149.60% increase in yield. The treatment also reduced accumulation of reactive oxygen species and enhanced the expression of antioxidant enzyme synthesizing genes-pod (3.49-fold), sod (3.63-fold), cat (3.68-fold) and plant defensin gene-pdf1.2 (2.60-fold) over the mock control in real time PCR analysis. Thus, formulated microbial consortium offers a promising eco-friendly strategy for managing BLB in cluster bean.