STATUS OF BACTERIAL WILT CAUSED BY RALSTONIA SOLANACEARUM IN PAKISTAN

Abstract

Field and laboratory investigations for distribution of bacterial wilt (BW) caused by Ralstonia solanacearum in different vegetable growing areas of Pakistan (during April-September 2008-09) revealed that sweet pepper was highly susceptible with overall incidence percentage of 21.9% followed by hot pepper (16.6%), tomato (13.3%), potato (10.5%) and brinjal (5.5%). Aggregate incidence in the whole country was 13.8%. Most of the isolates were obtained from soil (17.2%) and plant samples (18.8%). The disease was mainly distributed in Islamabad Capital Territory and Punjab with BW incidence of 19.2% and 13.9% respectively. Along with bacterial wilt a number of other diseases i.e. Verticillium and Fusarium wilt, Root knot nematodes (Meloidogyne spp.), Phytophthora rot (Phytophthora capsici), stem rot/Southern blight of tomato (Sclerotium rolfsii), Chilli leaf curl virus, bacterial blights (Xanthomonas compestris and Pseudomonas syringae) were found to be associated with the wilt syndrome of solanaceous crops. Most of the farmers were not certain about bacterial wilt symptomology and management. Mean values in BW affected areas were 9.9 soil pH, 29.5 oC, 71.59% RH and 71.86 mm rainfall. The tests further revealed that biovar 2 and 3 were more prevalent in Pakistan with 80 % majority of strains belonging to biovar 3. Predominant biovar in potato was biovar 2 (mostly in Northern territory of the country). Studies further revealed that rest of strains obtained from tomato, sweet pepper, hot pepper and brinjal were mainly biovar 3. In addition, some biovar 3 strains were also found to be associated with sweet pepper and