LAUSR

Abstract We selected six strains with in vitro antagonism against 15 South Asian strains of Ralstonia pseudosolanacearum from among 54 previously characterized Pseudomonas and other bacterial biocontrol strains and evaluated the value of integration of these biocontrol agents with partial host resistance of tomato in management of bacterial wilt. Biocontrol strains were almost four times more effective in suppressing bacterial wilt in IRAT L3, a partially resistant tomato line, than in L390, a highly susceptible line. Pseudomonas brassicacearum 93D8 and Wood 1R, and P. fluorescens Clinto 1 were the most effective strains with biocontrol efficacy of 68, 47 and 56% respectively, in IRAT L3. Bacterial wilt incidence was suppressed in IRAT L3 in four of four experiments by P. brassicacearum 93D8, and in three of four experiments by P. protegens Clinto 1 and P. brassicacearum Wood 1R. However, in L390, biocontrol efficacy of P. brassicacearum 93D8 and Wood 1R, and P. fluorescens Clinto 1 was 7, 15 and 12%, respectively. There was no correlation between in vitro antagonism of the biocontrol strains against R. pseudosolanacearum and in vivo biocontrol efficacy. These results highlight the value of integration of biocontrol agents with host resistance in management of bacterial wilt.