Bacterial wilt, a new disease of loofah caused by Pseudomonas solanacearum.
A previously unreported disease of loofah (Luffa cylindrica) was observed for the first time in fields in Touliu, in south-central Taiwan, in the summer of 1993. Diseased plants commonly occurred in patches and showed poor growth, stunting, vascular discoloration and wilting. Bacteria of the same colony type on Kelman's TZC medium were consistently isolated from the diseased plants. Loofah plants artificially inoculated with the isolated bacteria by either the stem prick or the soil infestation method produced similar symptoms as those observed in the field. The pathogen was reisolated from inoculated plants. The disease was identified as bacterial wilt caused by P. [Ralstonia] solanacearum based on cultural, physiological and biochemical characteristics and inoculation tests on various host plants. All tested bacterial strains from diseased loofah belonged to race 1, biovar 3, and were also pathogenic to other cucurbitaceous plants, tomatoes, eggplant [aubergines], sweet pepper [Capsicum], potatoes, tobacco and radish. However, strains of the bacterium from other hosts including tomatoes, tobacco, Capsicum, aubergines, potato, radish and perilla were not pathogenic to loofah. Three strains of R. solanacearum isolated from the roots of symptomless weed plants collected from the loofah fields were pathogenic to tomato, but only 1 was pathogenic to loofah. The 15 cultivars or lines of loofah tested were susceptible to the disease, however, the cultivars Seven Star F1 and Seven Beauty F1 had significantly less disease than other cultivars or lines.