Evaluation of Microbial Consortia of Trichoderma harzianum and Bacillus amyloliquefaciens for the Management of Groundnut Stem Rot under Controlled Conditions

Abstract

Groundnut (Arachis hypogaea L.), popularly known as peanut, is one of the most important oilseed and food legume crops cultivated worldwide. However, its cultivation is severely affected by stem rot disease caused by Sclerotium rolfsii, which leads to yield losses of up to 40%. The current study focuses on the management of Sclerotium rolfsii through the combined application of Trichoderma spp. and Bacillus spp. under field conditions. A roving survey conducted in major groundnut-growing areas of Trichy district, Tamil Nadu, revealed varying levels of disease incidence (46.00%–81.00%). The stem rot pathogen and antagonists were isolated from the surveyed locations and identified using morphological characteristics and molecular phylogenetic analyses based on ITS and 16S rDNA sequences, respectively. In vitro dual-plate assays revealed that Bacillus amyloliquefaciens BC-5 and Trichoderma harzianum TR-2 exhibited 82.22% and 86.66% inhibition, respectively, whereas paired-plate assays showed 78.27% and 75.55% inhibition against Sclerotium rolfsii. Scanning electron micrographs of Sclerotium rolfsii paired with effective Trichoderma and Bacillus isolates showed swollen hyphae with cell-wall damage, providing clear evidence of antagonistic interactions caused by volatile compounds produced by B. amyloliquefaciens and T. harzianum. At the field level, the combined application of effective B. amyloliquefaciens and T. harzianum performed better in reducing wilt disease incidence (77.90%) than the individual applications.