Prevalence and Occurrence of Various Wilt Pathogens Associated with Tomato (Solanum lycopersicum L.) in Togo

Abstract

In December 2015, wilt symptoms on tomato plants (Solanum lycopersicum L.) were observed on vegetable growing perimeters in Sotouboua district in Togo. The disease, manifested by wilting of the youngest leaves followed by wilting and total desiccation of plants who eventually dy, leading to losses of up to 100%, is similar to bacterial wilt. The aim of this study, was to determine the pathogen responsible for the observed symptoms. For this purpose, phytosanitary surveys were carried out on tomato plots in Sotouboua distric, in 2018. During the surveys, Tomato plants infected by wilt and the plots soil samples, were collected on CECODRI project and farmers’ plots in the district. Soil samples were analyzed for the detection of nematodes while, tomato leaves, stems and roots were directly observed under binocular loupe and after incubation in Petri dishes containing filter paper moistened with distilled water to encourage sporulation of phytopathogenic fungi. Infected tomato stems and roots were analyzed by stem-streaming and DAS-ELISA tests using Agdia inc. Ralstonia solanacearum Patho Screen Kit to detect R. solanacearum. The results of the phytosanitary surveys showed that the wilt prevalence was 100% in Sotouboua district with incidence rates of up to 100%. Analysis of diseased samples, using stem-streaming and DAS-ELISA tests, revealed that 85.11% of diseased plants were infected by R. solanacearum. No nematodes were identified in the roots of the infected plants, but in soil samples only a few nematodes were counted. No fungus was found in the plants with wilt symptoms. It appears, therefore that, the wilt on tomato plants in Sotouboua district was caused by R. solanacearum. This, in our knowledge, is the first report on R. solanacearum infection on tomato in Togo.