Abstract

Ralstonia solanacearum is a diverse species that differs in their host range and recently it showed pathogenicity to soybean crop and considered as seed-borne. In the present study, 21 pathogenic bacterial strains were isolated and purified from seeds of soybean (collected from fields of major soybean producing districts of Rajasthan state). These strains were characterized for their biochemical activities and subsequently three strains (KARA 72, 82 and 90) were subjected for 16S rRNA gene sequencing and phylogenetic study. Disease incidence and biological control of the pathogens were also studied. Incidence of the pathogen in different seed samples was figured 14–100% on the triphenyl tetrazolium chloride (TZC) agar medium. Studied pathogenic strains were diverse in their biochemical activities although all strains were positive for potato soft rot, nitrate reductase, oxidase activity and negative for levan production. The phylogenetic study of 16S rDNA sequences revealed that all three sequenced strains showed 100% sequence similarity to existing type strain R. solanacearum ATCC 11696 and R. solanacearum K60-1 11696 those were isolated from tomato in North Carolina, USA. In biological control study, it was found that P. fluorescens showed higher antagonistic activity (IA of 190.545 mm2) than B. subtilis (IA of 53.90 mm2) against tested wilt pathogen. The study has shown that wilt pathogen exists as seed-borne which can be a source of contamination for whole plant system and if not prevented it may cause a huge loss to the crop.