The various disease syndromes caused by Phytopthora capsici Leonian can be devastating to squash (Cucurbita spp.) production areas of the United States. In some growing seasons, yield loss has been reported up to 100%. A recently developed University of Florida Cucurbita breeding line, #394-1-27-12, resistant to the crown rot syndrome of P. capsici, was used to determine the inheritance of resistance to this disease. Data from F1, F2, and backcross progeny from crosses of a P. capsici-susceptible butternut-type winter squash (C. moschata) with #394-1-27-12 indicated that resistance is conferred by three dominant genes. The introgression of P. capsici crown rot resistance from #394-1-27-12 into morphologically diverse domesticates within Cucurbita will aid in the management of this economically important pathogen.
Confined-leaf tests in a greenhouse showed Lagenaria siceraria (Molina) Standley plant introduction (PI) 442369 was as susceptible to sweetpotato whitefly, Bemisia tabaci Gennadius, oviposition as Cucumis melo L., Cucurbita ecuadorensis Cutler and Whitaker, and Cucurbita lundelliana Bailey, whereas L. siceraria accessions PI 419090, PI 419215, PI 432341, and PI 432342 were resistant. Resistance rankings of L. siceraria accessions based on adult counts in greenhouse and field tests were similar. Adult entrapment among trichomes was highest on adaxial leaf surfaces of L. siceraria PI 419090. Abaxial leaf trichome density was 48.7/mm on sweetpotato whitefly-resistant L. siceraria PI 432342, 42.1/mm2 on Cucurbita lundelliana PI 540895, and ranged from 51.0 to 85.5/mm2 on Cucurbita ecuadorensis PI 540896. Leaf trichome densities of selected plants of four L. siceraria accessions ranged from 33.0 to 52/mm2 on the abaxial and from 6.3 to 20.8/mm2 on the adaxial surface. Scanning electron micrographs of the abaxial leaf surface, the preferred surface for oviposition, suggest that trichome configuration (density and arrangement of different lengths) could be a factor in reduction of whitefly oviposition on L. siceraria.
; Metwally et al., 1996 ; Padley, 2008 ). Cucurbita lundelliana is native to the Yucatan peninsula and can be hybridized with C. moschata , C. maxima , C. ficifolia , C. pepo , and C. argyrosperma ( Ferriol and Picó, 2008 ; Sitterly, 1972
cultivar Danmatmaetdol ( C. maxima ) ( Lee et al., 2001 ). Resistance to P. capsici from the wild species Cucurbita lundelliana was introgressed into 19 winter squash breeding lines ( Kabelka et al., 2007 ). An inheritance study indicated that