RFLP VARIATION AND GENETIC-RELATIONSHIPS IN CULTIVATED CUCUMBER

Two sets of cucumber (Cucumis sativus L.) germplasm were used to deter mine the potential use of restriction fragment length polymorphisms (R FLPs) for estimating genetic relationships. Sixteen accessions [15 dom esticated variety sativus and one feral variety hardwickii (PI 183967) ] of diverse origin were used to assess RFLP variation in cucumber, an d to determine if genetic relationships based on RFLPs were similar to those obtained by isozyme analysis. Additionally, 35 commercial lines or cultivars were surveyed to determine genetic relationships among a nd within common cucumber types (narrow genetic base). The 16 accessio ns were surveyed with 440 low copy clones from two libraries (Pst I pa rtial genomic and cDNA) using two restriction enzymes. Data from a sub set of 104 random (mapped and unmapped) and a set of 30 mapped RFLPs w ere used to estimate genetic relationships among the 16 cultigens. Var iability was low among RFLPs (33% of all probes) and putative alleles (similar to 2.2 polymorphic fragments/probe). RFLP variation between s ativus lines and hardwickii (21 +/- 4%) was greater than among sativus lines (12 +/- 2 %). RFLPs among the 16 accessions revealed genetic re lationships which agree with those obtained using isozymes. Genetic re lationships estimated using mapped and unmapped RFLPs were similar. Th e 35 elite lines were surveyed using a set of 40 RFLPs from 3 librarie s (Pst I and EcoR I partial genomic and cDNA) to evaluate the discrimi natory value of RFLPs among and between commercial cucumber types. The RFLP-derived genetic relationships among this germplasm were in agree ment with predictions based on fruit type and pedigree information. Th us, RFLPs are a useful addition to the morphological characters and is ozyme loci currently used for taxonomic classification and plant varie ty protection of cucumber.