Combined application of Pseudomonas fluorescens and Trichoderma viride has an improved biocontrol activity against stem rot in groundnut

Abstract

In an attempt to develop effective biocontrol system for management of stem rot disease in groundnut, 57 bacterial isolates and 13 isolates of Trichoderma spp. were evaluated for their antagonistic activity against Sclerotium rolfsii. The antagonists were selected based on their ability to inhibit the external growth of S. rolfsii from infected groundnut seeds. Four isolates of Pseudomonas fluorescens, GB 4, GB 8, GB 10 and GB 27, and T. viride pq 1 were identified as potent antagonists of S. rolfsii. T. viride pq 1 produced extracellular chitinase and parasitized the mycelium of S. rolfsii. Under controlled environment conditions, P. fluorescens GB 10, GB 27, T. viride pq 1 and the systemic fungicide Thiram® reduced the mortality of S. rolfsii inoculated to groundnut seedlings by 58.0%, 55.9%, 70.0% and 25.9%, respectively compared to control. In vitro growth of P. fluorescens GB 10 and GB 27 was compatible with T. viride pq 1 and Thiram®. Integrated use of these two bacterial isolates with T. viride pq 1 or Thiram® improved their biocontrol efficacy. Combined application of either GB 10 or GB 27 with T. viride pq 1 was significantly effective than that with Thiram® in protecting ground¬nut seedlings from stem rot infection.