Identification of multi-facial microbial isolates from the rice rhizosphere and their biocontrol activity against Rhizoctonia solani AG1-IA

Abstract

Identification of multi-facial biocontrol agents that could act against different pathogens of rice crop shall be an interesting approach to develop effective strategies of biocontrol in practice. To identify the promising multi-facial microbial isolates (MIs) from the rice rhizosphere, twelve native MIs which had already been tested against rice root-knot nematode (Meloidogyne graminicola) were screened in vitro against sheath blight pathogen of rice, Rhizoctonia solani AG1-IA. The MIs exhibited substantial variability in their ability to inhibit the mycelial growth of R. solani. Out of twelve, six most promising MIs were tested against R. solani under pot trials on rice cv. PusaSugandh-5. We observed 30–52% loss in plant growth with R. solani. However, soil treated with MIs significantly attenuated the adverse effect of sheath blight pathogen. Among the MIs, Pseudomonas putida AMUPP-1 was found to be most effective and suppressed the disease severity by 69% leading to a 21–49% improvement in plant growth. Furthermore, we observed that Trichoderma harzianum AMUTH-1, P. fluorescens AMUPF-1 and other MIs had lesser effectiveness compared to P. putida AMUPP-1. Interestingly, P. putida AMUPP-1 was also found to detoxify oxalic acid and able to produce ammonia, hydrogen cyanide, indole acetic acid, siderophore, and solubilized phosphorus. Moreover, validation trials under naturally infested field verified the effectiveness of P. putida AMUPP-1 with 61% improvement in rice yield. In addition to these, we also observed the effect of P. putida AMUPP-1 better than fungicide, propiconazole. The present study has identified the multi-facial nature of P. putida AMUPP-1 which effectively suppressed different group of rice pathogens, R. solani (in the present study) and M. graminicola (in a previous study).