Restriction fragment length polymorphisms (RFLPs) have been proposed for characterizing genetic diversity of maize (Zea mays L.) germplasm. 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 × dent line combinations (0.344). All flint and dent inbreds showed a smaller mean GS to lines from the other hererotic 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.

Restriction fragment length polymorphisms (RFLPs) have been proposed as a tool for assigning inbreds to heterotic groups and predicting heterosis and performance of single‐cross hybrids in maize (Zea mays L.). Such use was evaluated in 11 flint and 11 dent inbred lines from the European maize germplasm and in 66 F1 hybrids produced between them according to an incomplete factorial mating scheme. Inbreds and hybrids were evaluated for 12 forage yield and quality traits in three and six environments, respectively, in Germany. The RFLP assays of the 22 inbreds were performed with two restriction enzymes and 101 DNA probes distributed throughout the maize genome. Most (>97%) clone‐enzyme combinations revealed polymorphisms (⊄5.0 variants per clone‐enzyme combination). Genetic distances (GD) between lines, calculated from RFLP data, had a significantly greater mean for flint × dent (0.65) than for flint x flint (0.58) or dent × dent (0.59) line combinations. Cluster analysis based on GDs revealed associations among lines consistent with their origin from different heterotic groups and known pedigrees. The GD values pertaining to the 66 F1 hybrids were partitioned into general (GGD) and specific (SGD) genetic distances; GGD explained ⊄30% of the variation among GD values. Neither GD nor SGD was significantly correlated (|r|≤ 0.25) with F1 performance or midparent heterosis for any trait examined. Results from this study support previous investigations with U.S. maize germplasm in that RFLP data can be used for assigning inbreds into heterotic groups. However, RFLP‐based genetic distance measures are apparently not indicative of the performance of single‐cross hybrids between lines from different heterotic groups for forage traits.