ARS | Publication request: Response of Wild and Weedy Cucurbita L. to Pathotypes of Pseudoperonspora Cubensis (Cucurbit Downy Mildew)

Submitted to: Advances in Downy Mildew Research
Publication Type: Book/Chapter
Publication Acceptance Date: June 13, 2003
Publication Date: November 19, 2004
Citation: Lebeda, A., Widrlechner, M.P. 2004. Response of wild and weedy cucurbita l. to pathotypes of pseudoperonspora cubensis (cucurbit downy mildew). Advances in Downy Mildew Research 2:203-210.

Technical Abstract: The known host range of Pseudoperonospora cubensis encompasses about 50 species of approximately 20 genera of Cucurbitaceae, including Cucurbita. There is limited information on the response of various Cucurbita species to P. cubensis. There is only one recent paper demonstrating that host-parasite specificity between cultivars of C. pepo and P. cubensis is controlled by race-specific factors. A set of one hundred PI Cucurbita accessions (C. argyrosperma, C.cylindrata, C. digitata, C. ecuadorensis, C. ficifolia, C. foetidissima, C. maxima, C. okeechobeensis, C. pepo) was screened, by controlled inoculation, for resistance to eleven pathotypes of P. cubensis. The intensity of sporulation in leaf discs was evaluated 6-14 days after inoculation. Results revealed substantial differences in response among various Cucurbita spp. and accessions. Expression of incomplete resistance characterized by sparse sporulation was frequently recorded. Most of the reaction patterns showed clear pathotype (race)-specific resistance. Complete resistance to the studied set of pathotypes was not observed; however, some accessions of C. pepo var. texana showed susceptibility to all studied isolates. These results provide the first experimental evidence about the phenomenon of pathotype-specificity in a broad range of wild and weedy Cucurbita species.