Characterization of Ralstonia solanacearum isolates using biochemical, cultural, molecular methods and pathogenicity tests

Abstract

Bacterial wilt of tomato caused by Ralstonia solanacearum is one of the most destructive disease of tomato. A study was undertaken to characterize five isolates of Ralstonia solanacearum (from different regions of Uttrakhand (Pantnagar, Dehradun, Bilaspur and Kicha) and near Delhi) by biochemical, cultural, molecular methods and pathogenicity tests. The colonies of R. solanacearum on Nutrient Agar (NA) medium were smooth, circular, raised and dirty white. Colonies of R. solanacearum formed on Casamino Peptone Glucose (CPG) medium were white or cream-colored, irregularly round, fluidal and opaque, the colonies formed on TZC medium were white with pink centers. All the five isolates were gram negative, oxidase positive, catalase positive, reduced nitrate to nitrite, hydrolyzed Tween 80 and oxidized glucose. Molecular characterization of the suspected isolates was done. Total five suspected isolates showed the 281-bp amplification with the specific primers RS-F-759 and RS-R-760. This indicates the isolated bacterial cultures were R. solanacearum culture. The pathogenicity of test bacterium was established by Koch’s postulate under glasshouse condition and it was proved to be pathogenic.