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Poster: Biology & Disease Mgmt: Genetics of Resistance


Introgression of crown rot resistance into cultivated squash Cucurbita moschata, C. maxima and C. agyrosperma
S. ZHANG (1), Y. Fu (1), P. Moon (1), C. Waddill (1) (1) Tropical Research and Education Center, University of Florida, IFAS, U.S.A.

Phytophthora capsici incites crown rot in squash and often causes significant losses to growers worldwide. No resistance is available in commercial squash varieties, but resistance has been found in the wild species Cucurbita lundelliana and introduced into C. moschata, resulting in several resistant lines. However, the yields of these resistant lines are too poor to warrant their commercial release. To overcome this, four of these resistant lines were crossed with commercial varieties of C. moschata, C. maxima and C. agyrosperma in single or three-way crosses. The F1 progeny of C. moschata ‘Butterbush’ and C. moschata resistant lines were resistant to P. capsici and showed improved yield. Interspecific cross of ‘Buttercup’ (C. maxima) x 399 (432) (a resistant line) was made. The F1 progeny were completely resistant to P. capsici, and showed strong heterosis in plant growth and fruit size, but were male sterile. Backcross progeny exhibited low seed settings. Three-way crosses of C. agyrosperma x F1 (C. moschata x C. moschata) were obtained. The hybrids showed improved seed settings with higher percentage of normal seeds (41.2%) compared to the F1 interspecific progeny of C. maxima x C. moschata (8.8%). Embryo rescue was employed to overcome interspecific barriers. Further backcrossing with recurrent parents and pedigree selection for P. capsici resistance, high fruit yield, and flesh quality will be performed.