Evaluation of Tomato Cultivars for Resistance to Bacterial Wilt caused by Ralstonia Solanacearum
Abstract
Climate change impacts food production through altering the climatic suitability of agricultural areas for crops, pests and associated natural enemies. Bacterial wilt caused by Ralstonia solanacearum is a major constraint in tomato production leading to losses that amounts to 90% both in the open field and greenhouse conditions. The current methods used to manage the disease, are inadequate and pose both health and environmental risks. Host resistance has proved to be effective in management of bacterial wilt. The current study, evaluated 18 tomato varieties for resistance to R. solanacearum in the greenhouse. The experiment was laid out in a randomized complete block design with three replications and varieties were inoculated with 1× 108 cfu/ml of R. solanacearum. Incidence of bacterial wilt was assessed eight days after inoculation, by counting the number of wilted plants to determine percentage disease incidence and disease index reactions (DI) of each cultivar. Severity was recorded using a disease rating score of 0-4 and used to determine area under disease progress curve (AUDPC). Severity and incidence of bacterial wilt was significantly different (p <0.001) among the screened varieties. Six varieties including all non-hybrid varieties (Riogrande, Isisementi and Rionex) and three hybrid (F1) varieties Sifa F1, Danny F1 and Onyx F1were susceptible to bacterial wilt with disease index reaction (DI) of >30-70%. Among the F1 varieties, five varieties, Bravo F1, Kilele F1, Terminator F1, Big rock F1 and Ranger F1 had the lowest severity scores and incidences of bacterial wilt and were found to be tolerant to bacterial wilt with DI of 1-10%. Seven F1varieties were moderately tolerant and moderately susceptible with a DI of >10%-20% and >20-30% respectively. Despite the climatic risks and impacts on tomato production, tolerant cultivars can be recommended in the management of bacterial wilt for increased production and farmer incomes.
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