Identification of races and biovars among Ralstonia solanacearum isolates from Karnataka and Kerala

Twenty eight isolates of Ralstonia solanacearum from chilli, tomato, brinjal and potato were used for race detection based on host range and hypersensitivity test on capsicum leaves. All the 28 isolates infected the solanaceous crops viz., tomato, chilli, potato and brinjal in artificial inoculation and failed to infect other host differentials like ginger, mulberry and banana. In the hypersensitivity test, bacteria induced a dark brown necrotic lesion surrounded by a yellow halo after 48 h of inoculation in the infiltrated area followed by yellowing of leaves and extensive wilting. Thus, it was concluded that all the 28 isolates of R. solanacearum collected from different agroclimatic regions of Karnataka and Kerala belong to race-1. Isolates utilized all the sugar alcohols and disaccharides as evidenced by change in colour in the medium. This clearly indicated that all the isolates of R. solanacearum belong to biovar-III.