Prevalence of races and biotypes of Ralstonia solanacearum in India

Bacterial wilt caused by Ralstonia solanacearum is the most destructive disease of plants. Fifty-seven isolates of R. solanacearum causing wilt on different host plants viz., tomato (Solanum lycopersicum), brinjal (S. melongena), potato (S. tuberosum), bird of paradise (Strelitzia reginae), ginger (Zingiber officinale), chili (Capsicum annuum), capsicum (Capsicum annuum), davana (Artemisia pallens) and coleus (Coleus forskohlii) were collected from the different agro climatic zones of Karnataka and other parts of India. In this study, 57 isolates were differentiated into race on the basis of their pathogenicity and their ability to infect different host. The isolates were established as race-1. None of the isolates infected mulberry and banana. Fifty-four isolates oxidized and utilized both the disaccharides and sugar alcohols. These isolates were positioned as biovars-3 according to Haywards classification system. Three isolates from Kerala, two ginger, and one tomato strain were not able to utilize dulcitol and lactose. Hence, they were categorized into a new taxo group within the system and designated as biovar-3B for the first time in India. There were 54 isolates which were confirmed as race-1, biovar-3, and 3 isolates were confirmed as race-1, biovar-3B by morphological, physiological, biochemical and pathogenicity studies. Two sets of primers (OLI1 & Y2 and Y1 & Y2) were used in this study to authenticate the organism. Furthermore, the identity of the isolates was confirmed by a serological diagnostic kit obtained from the International Potato Research Center, Lima, Peru, and single chain variable fragment antibody specific to R. solanacearum.