Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: June 5, 2002
Publication Date: N/A
Technical Abstract: Genetic relationships among 970 cucumber plant introductions in the U.S. National Plant Germplasm System were assessed by observing variation at 15 isozyme loci. Allozyme frequency data of these PIs were compared to allozyme variation in heirloom and modern cultivars released between 1846 to 1985 and experimental commercial germplasm in use after 1985. Multivariate analysis defined four distinct groups of accessions, where Group A consisted of PIs received by the NPGS before 1992, Group B contained PIs from India and China obtained by the NPGS after 1992, Group C consisted of EC germplasm, and Group D contained H&M cultivars. Morphological and disease resistance evaluation data from the Germplasm Resources Information Network (GRIN) of the PIs examined were used in conjunction with estimates of population variation and genetic distance estimates to construct test arrays and a core collection for cucumber. The test arrays for resistance tolerance to angular leafspot, anthracnose, downy mildew, rhizoctonia fruit rot, target leafspot and water and heat stres consisted of 17, 16, 17, 16, 17, 16, and 16 accessions, respectively. The core collection that was developed consisted of accessions delineated in these test arrays (115) and 32 accessions that circumscribed the genetic diversity of the NPGS collection beased on their isozymic variation. The core collection represents about 11% of the total collection's size (115 +32 = 147). Given estimates of genetic diversity and theoretical retention of diversity after sampling, this core collection could increase the curatorial effectiveness and the efficiency of end-users as they attempt to identify potentially useful cucumber germplasm.