Control failures of Fusarium wilt on tomatoes and resistance of cultivars to the three races of the pathogen

Abstract

The use of resistant cultivars is the main strategy to control Fusarium wilt on tomato, caused by Fusarium oxysporum f. sp. lycopersici. This study aimed to quantify the incidence and distribution of this disease in the region of Nova Friburgo, RJ, as well as the type of resistance of tomato cultivars to the three FOL races. Samples of healthy and wilted plants from 40 properties were evaluated for the presence of vascular discouloration. Seventeen tomato cultivars were evaluated for resistance to the three FOL races using a grading scale. Classification for resistance/susceptibility, incidence and percentage of infection of the vascular system, fresh weight accumulation and seedling length were determined. All the cultivars analysed behaved as similar to immune (SI) to race 1 of FOL and similar to immune or partial resistance to race 2. Only Aguamiel cultivar presented a SI reaction to FOL race 3. None of the cultivars presented a SI reaction to the three races. It can be concluded that failures on the control of the disease in this region can be attributed to the majority use of cultivars with incomplete resistance to the three FOL races. The seed packages also contain incomplete information about FOL resistance.