LINKAGES AMONG RFLP, RAPD, ISOZYME, DISEASE RESISTANCE, AND MORPHOLOGICAL MARKERS IN NARROW AND WIDE CROSSES OF CUCUMBER

A 58-point genetic map was constructed with RFLP, RAPD, isozyme, morph ological, and disease-resistance markers spanning 766 cM on ten linkag e groups for a cross within the cultivated cucumber (Cucumis sativus v ar. sativus). Relatively few DNA polymorphisms were detected, agreeing with previous studies documenting a narrow genetic base for cucumber. Most RFLPs within the cultivated cucumber appear to be changes at res triction-enzyme sites. Sixty-four percent of RAPD markers that fit exp ected ratios at P<0.001 were unlinked, possibly due to poor amplificat ion and the inefficiency of dominant markers to detect linkage in an F -2 family. A 70-point linkage map, spanning 480 cM on ten linkage grou ps, was constructed with RFLP, isozyme, morphological, and disease-res istance markers for a cross between the cultivated cucumber and the wi ld or feral C. sativus var. hardwickii. Unlinked markers and more link age groups than chromosome pairs indicated that both maps were not sat urated. Twenty-one markers doubly segregated in both families and regi ons of colinearity were identified.