Estabilidade da resistência de 'Ohio 8245' e 'Heinz 9553' à mancha bacteriana do tomateiro

bacterial spot is one of the major diseases of both processed and fresh-market tomato crops. the disease causes defoliation, which decreases yield and exposes fruits to sunscald. in this work, resistance levels of 'ohio 8245' and 'heinz 9553' to the four bacterial spot xanthomonads are reported in order to evaluate these cultivars as patterns and/or sources of resistance. the trial was carried out in greenhouse conditions, in a split-plot completely randomized block design with three replications. the main plot was "isolate", whereas the subplot was "cultivar". three isolates of each species were inoculated at the seedling stage. incubation period and severity (leaf diseased area percentage, lda%, and area under disease progress curve, audpc) were evaluated. interaction was detected among factors for all variables. no differences in the incubation period among cultivars were detected, except for the isolate cnph 142-t of x. vesicatoria, which was less for the cultivars 'ohio 8245' and 'heinz 9553'. differences among isolates were detected only in 'heinz 9553', with the least values for isolates of x. vesicatoria and x. perforans. for the majority of isolates, less lda% was observed for cultivars ohio 8245 and heinz 9553. on the other hand, for audpc, 'ohio 8245' had the least value followed by 'heinz 9553'. it is suggested that these both cultivars have broad spectrum quantitative resistance which can be used for breeding studies.