Antibacterial Effect of Farm Compost Enriched with Trichoderma virens against Ralstonia solanacearum, the Causative Agent of Bacterial Wilt in Tomatoes

Abstract

Tomato cultivation is economically important from Ivory Coast in Africa. However, it is exposed to various soil pathogens, among which bacterial wilt is one of the most feared. The present study aims to optimize tomato production by controlling R. solanacearum through the use of Trichoderma virens in farmyard compost as an ecological and sustainable solution. The work was organized into two main parts : an in vitro analysis of the effect of T. virens extract on the growth of R. solanacearum and the characterization of the impacts of T. virens-enriched compost on the development of Petomech tomato plants in the presence of R. solanacearum in a semi-controlled environment. In vitro, three concentrations (25, 50, and 100 mg/mL) of T. virens extract and two strains of R. solanacearum (RUN 1539 and 1822) were used. The methodology used was the diffusion test. In a semi-controlled environment, two spore concentrations of T. virens (10⁶ and 10⁸ spores/mL) with two volumes of solutions (300 and 400 mL) were introduced into the compost. Various composite proportions of 25%, 50%, and 75% of this amended compost were used in the culture medium for the tomato plants. The results showed that the crude extract of T. virens significantly inhibited the growth of strains 1539 and 1822 at a concentration of 100 mg/mL, with 1.08 mm and 2.2 mm, respectively. In the greenhouse, a significant reduction in wilting (WI) and colonization (CI) indices was observed with the use of compost enriched with 75% T. virens at a volume of 400 mL of inoculum. These treatments significantly improved the agronomic parameters of tomato plants. Treatments combining high concentration (C2 = 10⁸ spores/mL) with compost proportions of 50% and 75% led to the best results, reducing the disease by 90%.  This study showed that the results obtained demonstrated a dose-dependent inhibition of R. solanacearum by T. virens. Thus, the results demonstrate that the combination of T. virens and compost constitutes a promising strategy for biological control of bacterial wilt in tomato caused by R. solanacearum.