SELECTION FOR MULTIPLE DISEASE RESISTANCE REDUCES CUCUMBER YIELD POTENTIAL

Experiments were conducted in Wisconsin and Michigan to determine whet her selection for multiple disease resistance adversely affects yieldi ng ability of commercial cucumber (Cucumis sativus var. sativus L.; CS ) lines. Inbred F4 and F5 lines were developed from C. sativus var. ha rdwickii (R.) Alef. (CH) x CS which had been either selected or not se lected for resistance to the causal organisms of scab, anthracnose, an d downy mildew. The exotic CH germplasms possesses a multiple fruiting habit with high yield potential and the CS genotypes include several disease resistance. In each comparison between selected and unselected progeny, the unselected families either significantly outyielded, or were not significantly different than their selected counterparts. In no case did the selected progeny outyield the unselected progeny. Sinc e this was observed for both fruit number per plant and total fruit we ight per plant, and it occurred despite differences in fruit size, we conclude that selection for disease resistance led to a reduction in y ield potential in these populations.