Potential of Bio Control Agents in Management of Groundnut Seedling Diseases

Abstract

Groundnut (Arachis hypogaea L.) is an important oilseed legume crop vulnerable to seed and seedling diseases such as collar rot and stem rot caused by Aspergillus niger and Sclerotium rolfsii, respectively which leads to significant early plant stand losses. In view of environmental concerns associated with chemical fungicides, the present study evaluated native microbial bioagents as sustainable alternatives for disease management. A total of 97 microbial isolates were isolated from groundnut rhizosphere soil (39 no.), healthy plant parts (internal stem and root tissue- 42 no.) from farmers’ fields of Wanaparthy, Warangal and Mahaboobnagar districts.) in addition to seven bacterial isolates from cow urine (3 no.) and cow dung (4 no.). The isolates were screened for antagonistic activity against S. rolfsii and A. niger using the dual culture technique wherein, seven isolates have exhibited significant inhibition, ranging from 65.25–90.50% against S. rolfsii and 60.75–80.50% against A. niger. Among these, Bacillus sp. (IR 10) and Pseudomonas sp. (IC 8) were selected for further evaluation. Broth formulations were used for seed treatment, and talc-based formulations were applied for soil application and combined seed treatment plus soil application in pot culture studies using groundnut cv. K6. Results of the study indicated that, in case of S.rolfsii, seed treatment with Bacillus sps. recorded maximum per cent seedling emergence of 68.50% and was on par with seed treatment cum soil application of Bacillus spp. which showed 65.83 % emergence; and minimum seedling mortality of (22.67%) and (26.50%), respectively. However, seed treatment with Pseudomonas sps. (IC 8) showed 60.17 % emergence. With respect to A.niger, maximum per cent seedling emergence (66.50 %) and minimum seedling mortality of (21.83%) was recorded by seed treatment cum soil application of Bacillus spp. with no significant difference with seed treatment by Bacillus sp (65.50%) for seedling emergence. However, the per cent improvement of seedling emergence by the treatment, seed treatment with Bacillus sp. (IR 10) was 54.49% and 57.36 % reduction of seedling mortality over pathogen control against S.rolfsii. While, the per cent improvement of seedling emergence by seed treatment cum soil application of Bacillus spp. was 55.38% and 61.13% reduction of seedling mortality against A.niger. The study concludes that seed and soil application of carrier-based Bacillus bioformulations is an effective and environmentally sustainable strategy for managing seed and seedling diseases of groundnut under integrated disease management systems.