Indigenous bacterial consortia for growth promotion and biocontrol of tomato root pathogens in tropical agroecosystems

Widespread use of pesticides for crop disease management raises environmental and health concerns but exploring indigenous rhizobacteria as eco-friendly alternatives can help mitigate this issue. In the study, 11 (7 Bacillus and 4 Pseudomonas) isolates were selected based on demonstrated plant growth-promoting (PGP) and biocontrol potential. Selected bacterial isolates exhibited significant antagonistic activity against pathogenic fungi, Sclerotium rolfsii and Fusarium oxysporum f. sp. lycopersici. Several known genes for antibiotic, HCN and lytic enzyme production were identified, with Pseudomonas isolates also demonstrating siderophore production capabilities. Greenhouse trials revealed that seed inoculation with the bacterial strains caused a significant increase in plant biomass (80%), shoot length (74%), and root length (126%). The PGPR strains were developed into four consortia (C1-C4) and inoculated into tomato seeds, seedlings, and soil which successfully suppressed the incidence of root diseases and promoted plant growth both in greenhouse and field conditions. Application of bacterial consortia as a talc-based formulation to seeds and soil yielded enhanced plant growth (87.5%) and suppressed infection by Sclerotium rot and Fusarium rot and wilt (73%). In the field trial, C4-treated plots showed approximately 40% increase in fruit yield compared to the control which was the overall highest amongst the treatments. Furthermore, qPCR analysis demonstrated the persistence of the introduced strains in the rhizosphere, while endpoint PCR confirmed their endophytic colonisation. Overall, this study highlights the effectiveness of native PGPR consortia as a sustainable tool for improving plant health and enhancing crop yield.