Stem rot (Sclerotium rolfsii) suppression and yield enhancement potential of native PGPR of peanut (Arachis hypogaea)

Stem rot of peanut, caused by the fungus S. rolfsii, is a significant disease occurring worldwide and leads to considerable yield losses. Due to the adverse effects of chemical fungicides, biological control methods have gained importance in recent years. The efficacy of biocontrol can be enhanced by applying indigenous strains that effectively suppress and compete with in situ pathogenic microorganisms. In this study, native PGPR isolates from the genera Bacillus and Pseudomonas were isolated and tested for their antagonistic activity against S. rolfsii, growth-promoting ability and yield enhancement in peanuts under both in vitro and in vivo conditions. The potential PGPR isolates were subjected for partial sequencing of the 16S rRNA gene and identified as B. subtilis PB(20d), B. amyloliquefaciens PB(40d), B. subtilis PB(50d), Paenibacillus campinasensis PB(60d) and Pseudomonas aeruginosa PP(30d). The phylogenetic tree organized these strains into their clades alongside reference strains from the NCBI database. Results from pot culture and field experiments revealed that the treatment with the combination of identified PGPR strains exhibited a lower incidence of stem rot and a higher yield of peanuts compared to individual applications and control treatment. Therefore, the combined application of native PGPR strains has proven to be more effective in addressing the variability in the performance of individual biocontrol agents and improving overall efficacy.