Synthetic Elicitor-Induced Defense Responses in Tomato (Solanum lycopersicum) Cultivated in Côte d’Ivoire against Bacterial Wilt Caused by Ralstonia solanacearum
Tomato is the most consumed vegetable in Côte d’Ivoire because it is used to cook most sauces and all forms of salad. Tomatoes annual yield fluctuates between 22,000 and 35,000 tons. The yield remains below demand. Several factors can explain these low yields. Among them, biotic factors are the most important. Among bacterial diseases impacting negatively tomato yield, bacterial wilt caused by Ralstonia solanacearum is a dangerous one that causes serious damage in the nursery as well as in plantation. It can cause up to 100% yield loss depending on the variety. Bacterial wilt caused by Ralstonia solanacearum still constitutes tomato (Solanum lycopersicum) economical disease in the world. This disease is favored by very humid soils and high temperatures. Genetic control currently used is the most effective strategy. Disease control in crops has also become possible through the induction of plant defense reaction. This work aims at assessing the effect of both synthetic elicitors (BABA and ASM) supposed to induce tomato defense reaction against bacteria and particularly Ralstonia solanacearum. BABA and ASM solutions were each applied at concentrations of 5 to 100 ppm on R. solanacearum in vitro, and its growth was recorded. Then, the in vivo development of bacterial wilt was assessed following different elicitors application modes to both local tomato cultivars Tropimech and Caraïbo respectively sensitive and tolerant to this disease. Up to 100 ppm, BABA and ASM elicitors showed no antibacterial effect against R. solanacearum. However, these elicitors revealed a protective action against the development of bacterial wilt after inoculation of R. solanacearum. Compared to leaf treatment, the supply of elicitors to roots or successively to roots and leaves reduced the development of bacterial wilt by more than 50%. Both tomato varieties (Tropimech and Caraibo) expressed identical resistance levels facing Ralstonia solanacearum after BABA and ASM application. The elicitation of tomato plants could be an ecological approach for effective control of R. solanacearum. It is concluded that control bacterial wilt caused by R. solanacearum using ASM and BABA as elicitors of tomato defense. Two tomato cultivars that are Tropimech and Caraïbo respectively sensitive and tolerant to bacterial wilt were used. Tropimech which is the sensitive cultivar expressed identical resistance levels facing Ralstonia solanacearum after BABA or ASM application as Caraibo, the tolerant cultivar. Thus, ASM and BABA can be used in control to bacterial wilt of tomato. This technique can be considered as an ecological approach and an alternative to chemical control of bacterial wilt caused by R. solanacearum in tomato.
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