INTERACTIONS BETWEEN RACE-2 OF FUSARIUM-OXYSPORUM F SP LYCOPERSICI AND NEAR-ISOGENIC RESISTANT AND SUSCEPTIBLE LINES OF INTACT PLANTS OR CALLUS OF TOMATO

The interaction between Fusarium oxysporum f. sp. lycopersici race 2 and near-isogenic resistant and susceptible tomato lines of the cultivar Moneymaker and callus cultures derived from these lines was studied. Resistance was expressed in callus tissue for a short period, during 4 days after inoculatiOn. This was shown by a delay in fungal growth on callus tissue derived from resistant plants. Accumulation of the phytoalexin rishitin was similar in callus tissue and whole plants. Tomato plants resistant to race 2 did not accumulate more rishitin than susceptible plants during the first 4 days after inoculation, in contrast to plants resistant to race 1 and inoculated with race 1. The different response of tomato plants and calli towards race 1 and 2 of F. oxysporum f. sp. lycopersici suggests that the mechanism of resistance controlled by the I-1 and the I-2 gene is different. Callus tissue might be useful to study these differences in resistance.