Identification of the race of Pseudomonas solanacearum causing wilt of solanaceous vegetables in West Bengal and its survival.
P. solanacearum [Ralstonia solanacearum], the causal agent of wilt of aubergine, tomato, potato and chilli (Capsicum) was isolated from different fields in West Bengal, India, and the race status of the isolates was investigated. Pathogenicity and biochemical parameters were used for identification of the races. Oxidation of different sugars, sugar alcohols and denitrification properties were examined. The results indicated that all the isolates, irrespective of the host, were race 1. The short and the long term survival of the pathogen in the carposphere, in natural soil as well as in weed hosts, as primary sources of infection, was also examined using a streptomycin and erythromycin resistant double marker strain of the pathogen. The results indicated that race 1 of the pathogen could survive more than 6 months on the seed surface and in the soil. Furthermore, R. solanacearum could survive in the rhizosphere, on the rhizoplane and inside the roots of a large number of weed plants (Solanum nigrum, S. anguivi, S. torvum, S. xanthocarpum, Croton bonplandianum, Euphorbia hirta, Colocasia esculenta, Portulaca oleracea, Phyllanthus niruri and Parthenium hysterophorus) of West Bengal. The epidemiological significance of the survival of race 1 in seed, soil and weed plants is discussed in relation to the development of a disease management programme.