RELATIONSHIPS AMONG EARLY EUROPEAN MAIZE INBREDS .1. GENETIC DIVERSITY AMONG FLINT AND DENT LINES REVEALED BY RFLPS

Restriction fragment length polymorphisms (RFLPs) have been proposed for characterizing genetic diversity of maize (Zea mays L.) ge-plasm. Fifty-seven elite inbred lines representative of early-maturing European flint and dent heterotic groups were assayed for RFLPs with 188 clone-enzyme combinations (98 genomic DNA clones, 2 restriction enzymes). Objectives of this study were to (i) investigate the amount of variation for RFLPs in these materials, (ii) determine the level of genetic diversity within and between heterotic groups, and (iii) examine the usefulness of RFLPs for assigning inbred lines to heterotic groups. All DNA clones detected polymorphism with at least one enzyme. About half of all RFLP patterns were common to the flint and dent lines, and a quarter was specific to the lines of each heterotic group. Genetic similarity (GS), calculated from RFLP data as Dice's similarity coefficient, ranged from 0.25 to 0.72 between unrelated pairs of lines. Mean GS for unrelated line combinations within the flint (0.425) and dent (0.414) heterotic groups were considerably greater than for flint x dent line combinations (0.344). All flint and dent inbreds showed a smaller mean GS to lines from the other heterotic group than to unrelated lines from the same heterotic group. For lines of mixed origin, the difference in mean GS to flint lines and to dent lines was consistent with the expected genomic proportions from each heterotic group based on pedigrees. Principal coordinate analysis of GS estimates resulted in a separate grouping of flint and dent lines. Results from this study corroborate the usefulness of RFLPs for identification of lines for assigning inbreds into heterotic groups. For the latter purpose, it seems possible to confine RFLP assays to a smaller number of clone-enzyme combinations with increased discriminatory power between lines from different heterotic groups.