Evaluation of potential actinomycetes Bioformulation on stem rot of groundnut caused by sclerotium rolfsii

Abstract

Groundnut (Arachis hypogaea, L.) is one of the most important oil seed crops of India. Stem rot caused by Sclerotium rolfsii Sacc. is a major constraint in the production and productivity of the groundnut? Though chemical fungicides have played an important role in increasing groundnut production and management of stem rot, their indiscriminate use for the control of the disease has led to several environmental problems. Thus, other alternative disease management options were considered among which biological control appears to be promising. Biological control with potential actinomycetes is receiving greater attention all over the world. Roving survey was conducted in groundnut growing regions of Andhra Pradesh. 50 actinomycete isolates were isolated, twenty actinomycete isolates were tested for their growth rate and antifungal activity against groundnut stem rot pathogen, S. rolfsii under in vitro conditions using dual culture method. Among twenty isolates of actinomycetes, five isolates showed maximum inhibition of S. rolfsii. These five isolates were characterized based on cultural, biochemical and molecular characters. Among the five actinomycete isolates (Ggd, Kdr, Kyd, Lrp and Mkc), three potential isolates were selected for preparation of bioformulations. The efficacy of talc-based formulations of Ggd, Kdr and Kyd were evaluated against S. rolfsii for their ability to reduce the stem rot incidence of groundnut under glasshouse conditions. Among different treatments, (T13) seed treatment with talc-based formulation of Ggd isolate @ 5g / kg seed + soil application @ 5 g / 5 kg soil at 30 DAS was found to be superior in reducing the stem rot incidence showing lowest per cent disease incidence of 7.2, 9.6, 17.4 and 26.6 at 30, 60, 90 and 105 DAS respectively.