Biocontrol of bacterial seedling blight of rice caused by Burkholderia gladioli using with its avirulent isolate

Abstract

Soaking rice seeds in a bacterial suspension (1×10⁸cfu/ml) of an avirulent isolate of Burkholderia gladioli (1064A) for 6 days at 15°C before sowing markedly suppressed the incidence of bacterial seedling blight caused by B. plantarii. Similarly all 16 virulent isolates of B. gladioli tested suppressed the disease, while 30 bacterial isolates belonging to the genus Acidovorax, Burkholderia (except B. gladioli), Pseudomonas and Ralstonia did not. The isolate 1064A decreased the cell number of B. plantarii co-inoculated in germinating seedlings by 1/10 to 1/100 that of the nontreated. It also markedly decreased the accumulation of tropolone, a B. plantarii toxin, in seedlings and soil. The isolate was effective against 12 strains of B. plantarii. The strain revealed a remarkable biocontrol effect when rice seeds, which have been inoculated with B. plantarii at the flowering stage and harvested in the previous season, were used as a material. Because the isolate was not virulent on 23 species of crops tested, it seems to be a promising biocontrol organism against bacterial seedling blight of rice.