DIVERSITY OF HISTORICALLY IMPORTANT SWEET CORN INBREDS AS ESTIMATED BY RFLPS, MORPHOLOGY, ISOZYMES, AND PEDIGREE

Historical records indicate that sweet corn (Zea Mays L.) germplasm is largely derived from the Northern Flint race of corn. In addition, most of the publicly available inbreds were derived from three cultivars: 'Stowell's Evergreen', 'Country Gentleman', and 'Golden Bantam'. In order to better understand sweet corn germplasm, 43 historically important sweet corn inbreds and three dent corn inbreds were examined by pedigree information, restriction fragment length polymorphisms (RFLPs), isozyme markers, and morphological traits. Data sets were developed from 71 RFLP probes, 27 isozyme loci, 24 morphological traits, and pedigree coefficients of relationship, and these data sets were subjected to cluster analysis. Isozymes and especially morphology did not accurately group these inbreds according to known pedigree relationships. The RFLP distance showed good agreement with pedigree distance (r = 0.54**). Based on cluster analysis of these two data sets this sweet corn germplasm can be divided into two major groups, inbreds that contain Golden Bantam germplasm, and inbreds with Stowell's Evergreen, Country Gentleman germplasm, or both. Several inbreds were not closely aligned with either group, and these unique inbreds have been widely used by sweet corn breeders. The amount of genetic diversity present in this material, with an average of 2.22 alleles per isozyme locus and RFLPs averaging 4.14 variants per probe, is within the range of diversity reported for Corn Belt Dent inbreds.