Isolation and Characterization of Biocontrol Microbes for Development of Effective Microbial Consortia for Managing Rhizoctonia bataticola Root Rot of Cluster Bean Under Hot Arid Climatic Conditions

Development of native microbial consortia is crucial for the sustainable management of plant diseases in modern agriculture. This study aimed to evaluate the antagonistic potential of various microbial isolates against <i>Rhizoctonia bataticola</i>, a significant soil-borne pathogen. A total of 480 bacteria, 283 fungi, and 150 actinomycetes were isolated and screened using in vitro dual plate assays. Among these, isolates 5F, 131B, 223B, and 236B demonstrated the highest antagonistic activity, with inhibition rates of 88.24%, 87.5%, 81.25%, and 81.25%, respectively. The selected isolates were further assessed for abiotic stress tolerance, revealing their ability to thrive under extreme conditions. Characterization of biocontrol and plant growth-promoting activities revealed the production of siderophores, hydrogen cyanide, ammonia, chitinase, and indole-3-acetic acid, along with the solubilization of zinc and phosphorus. Compatibility tests confirmed the potential of forming effective microbial consortia, which significantly reduced the percent disease index in cluster bean. The most effective consortium, comprising <i>Trichoderma afroharzianum</i> 5F, <i>Pseudomonas fluorescens</i> 131B, <i>Bacillus licheniformis</i> 223B, and <i>Bacillus subtilis</i> 236B, achieved a 76.5% disease control. Additionally, this consortium enhanced total phenol (92.1%), flavonoids (141.6%), and antioxidant defense enzyme activities including POX (188.5%), PPOX (116.3%), PAL (71.2%), and TAL (129.9%) in cluster bean plants over the infected control, leading to substantial improvements in systemic resistance of plants. This consortium also significantly enhanced plant height, fresh weight, dry weight, number of pods per plant, and seed yield over the infected control as well as mock control. This study underscores the potential of these robust microbial consortia as a sustainable and effective strategy for managing <i>R. bataticola</i> and enhancing crop productivity under extreme environmental conditions.