Rhizosphere and endophytic bacteria for the suppression of eggplant wilt caused by Ralstonia solanacearum

Abstract

Forty eight endophytic bacteria and 101 rhizobacteria were screened for their antibacterial activity against Ralstonia solanacearum, causal agents of eggplant wilt. Among 22 effective antagonistic isolates, 18 were Pseudomonas spp. forming three groups based on biochemical characterization. Talc formulation of the antagonistic bacteria and non-formulated 24 h old grown antagonistic bacterial cells was evaluated in the greenhouse condition for the suppression of eggplant wilt. Talc formulation of two species of Pseudomonas (RBh41 and RBh42) completely suppressed the incidence of wilt up to 36 days of inoculation. Treatment with bacterial cells of Pseudomonas mallei (RBG4, ET17) and one Bacillus spp. (RCh6) reduced wilt incidence of 83 percent compared to control. Talc formulations of seventeen isolates of antagonistic bacteria were prepared and used for treating the nursery and seedlings during transplanting. Biocontrol efficiency of 100 percent was recorded in Bacillus sp. (RP7) treatment and 80 percent was recorded by EB69, RCh6 and RBG4 treatments during 2007-08. During 2008-09, EB69 recorded 100 percent biocontrol efficiency followed by RP7 (96 percent), RCh6 (93 percent). Yield increase of over 80 percent was recorded in RP6 and EB69 treatments followed by RBG4 treatment. EB69, RBG4 (Pseudomonas sp.) and reduced wilt over 65 percent and increased the yield (75 percent) consistently over the two years and hence these isolates could be considered for developing potential biocontrol agents with plant growth promoting characteristics for management of R. solanacearum in eggplant.