Identification of the causal pathogen of bacterial wilt disease in cucurbitaceous crops and bean and its alternative weed hosts in Sri Lanka

Bacterial wilt caused by Ralstonia solanacearum is a destructive disease and one of the major constraints in vegetable production of Sri Lanka. Outbreak of bacterial wilt disease occurred in recent years for the first time in cucurbits and bean cultivated fields with 50-100% disease incidence. Hence, the present study was carried out with the objectives of isolation and molecular identification of causal pathogen of bacterial wilt of cucurbits and beans and to identify the weed hosts that harbour the bacterial wilt pathogen. Based on morphological and PCR analysis, gene sequence and homology search results, the causal pathogen of bacterial wilt disease in Momordica charantia, Cucumis sativus, Luffa acutangula, Cucurbita maxima, Cucumis anguria, Citrullus lanatus and Phaseolus vulgaris in Sri Lanka were identified as R. solanacearum with 99.37-100% similarity with Gene bank Accession CP022795.1, CP025986.1 and MF373815.1 of R. solanacearum. Twenty five out of 28 weeds species collected from Bacterial wilt infected fields were identified as symptomless carriers of R. solanacearum. All eight isolates from cucurbits and bean and 25 weeds species belong to biovar 3 and race 3 of R. solanacearum. This is the first report of R. solanacearum causing bacterial wilt in cucurbits, bean and weeds in Sri Lanka.