Aggressiveness to pumpkin cultivars of isolates of Phytophthora capsici from pumpkin and pepper

Nine isolates of Phytophthora capsici obtained from pumpkin and pepper in d iverse geographic areas, including Korea, France, Italy, and the United Sta tes, were evaluated for their ability to cause disease on nine Korean and J apanese pumpkin cultivars under controlled environmental conditions. No hyp ersensitive type of resistance was observed in any of the pumpkin cultivars inoculated with P. capsici. Disease incidence ranged from low to high, ind icating varying levels of partial (quantitative) resistance. In addition, a significant cultivar-isolate interaction was observed, indicating that hos t specialization was present in some cultivars. Disease severity increased with inoculum density of P. capsici. The Korean cultivar Danmatmaetdol was highly resistant to the I! capsici isolates tested, suggesting that economi c levels of resistance exist in pumpkin. The pumpkin isolates from all loca tions caused more disease than the pepper isolates to all the pumpkin culti vars tested. Soil-drench and stem-wound inoculation methods were more relia ble than a foliar-inoculation method for evaluating pumpkin cultivar resist ance.