Biological control of groundnut stem rot caused bySclerotium rolfsii(Sacc.)

In dual culture, one among the three isolates of Trichoderma viride, an isolate in each of T. harzianum and Pseudomonas fluorescens were inhibitory to the growth of Sclerotium rolfsii (Sacc.), the causal agent of stem rot of groundnut. The isolate Tv1 of T. viride caused 69.40% inhibition of the mycelial growth of the pathogen followed by P. fluorescens resulting in 64.40% inhibition. Among the five, T. viride (Tv1) and P. fluorescens (Pf1) were most effective in suppressing sclerotial formation. The culture filtrate of Tv1 inhibited the growth of the pathogen (87.05%) as well as sclerotial germination (62.50%) to a greater extent than others. Due to the antagonistic effect of the biocontrol agents germination of sclerotia was also poor. Among the organic amendments tested in greenhouse, mahuacake with T. viride each @ 5 g/kg of soil resulted in 3.75% stem rot incidence as against 39.98% in control. Enhanced activities of defence-related enzymes viz., peroxidase (PO) and polyphenoloxidase (PPO) were noticed in infected plants rather than in healthy ones. Although induction of PO as well as PPO was observed in diseased plants, additional increase in activities of these enzymes were observed in plants treated with either P. fluorescens or T. viride.