Incidence, severity and characteristics of <i>Ralstonia solanacearum</i> species complex in greenhouses in Southern Ghana

Abstract

Tomatoes are important component in Ghanaian diets, but bacterial wilt disease has become a major threat to the production of this high value vegetable. Consequently, relevant stakeholders over the past decade have sited greenhouses in the South of the country to boost tomato production, with some operators reporting wilt symptoms of tomato in their greenhouses. This study was therefore conducted with the aim of determining incidence and severity of the bacteria wilt disease of tomato; isolate causal organism from diseased tissues, establish sources of the bacteria inoculum in greenhouses and characterize isolates using morphological, biochemical and molecular techniques. Koch's postulate was also carried out on the isolates. Bacteria wilt disease was recorded in 12 out of 54 greenhouses surveyed. Incidence and severity of the disease within greenhouses ranged from 5.9%-18.5% and 0.5 – 1.2, respectively. Ralstonia solanacearum species complex was confirmed through streaming, morphological and biochemical tests. Strains of Phylotypes I and III (now R. pseudosolanacearum) were determined by multiplex polymerase chain reaction. Sources of bacteria inoculum in the greenhouses were found to be irrigation water and the growth substrate used. Koch's postulate was fulfilled. Accurate diagnosis of the pathogen is a major step towards developing effective disease management tools in the country and beyond.