Fusarium oxysporum associated with wilt and root rot of tomato in Queensland; races and vegetative compatibility groups

Abstract

Twenty-two isolates of Fusarium oxysporum, from Queensland's major tomato growing areas, were studied in glasshouse pathogenicity tests and assessed for vegetative compatibility. Isolates of Fusarium oxysporum f. sp. lycopersici were identified to race using pathogenicity tests with 4 differential tomato cultivars: Grosse Lisse, Scorpio, moradade and Delta Tristar. The occurrence of race 3 in the Bundaberg district in 1988 was established. In glasshouse experiments, Fusarium wilt severity was influenced by inoculum concentration (1 x 106 v. 5 x 106 conidia/ml). Pathogenic and non-pathogenic isolates were distinguished by vegetative compatibility group analysis. However, all races were in a single vegetative compatibility group and could not be differentiated using this technique. Isolates collected from discoloured vascular tissue in the lower stems of plants with severe root rot (Pythium spp. associated), were non-pathogenic to tomato, bean and pea, although some isolates caused slight damage to cucumber. These isolates were distinctly different from Fusarium oxysporum f. sp. radicis-lycopersici, the cause of root and crown rot.