Organization of RFLP diversity among inbred lines of maize representing the most significant heterotic groups

One hundred-sixteen inbred lines of maize (Zea mays L.) from significant heterotic groups (i.e., European flint, Lancaster Sure Crop, Minnesota 13, and Reid Yellow Dent) and miscellaneous origins were assayed for restriction fragment length polymorphism (RFLP). Our goals were to investigate (i) genetic variability and its structure among and within heterotic groups and (ii) the use of RFLP markers to assign miscellaneous lines to heterotic groups by means of probes selected for lotus specificity, clear patterns, and reproducibility. Among the 63 single copy probe-enzyme combinations used, 372 variants were scored with a mean of 5.9 variants per combination. Principal component and cluster analyses performed on lines from established heterotic groups clearly separated hint lines from dent lines. Loci that contributed the most to the genetic differentiation between European flint and northern U.S. dent lines were determined. Within U.S. germplasm, classification showed an association of inbreds that closely matched associations based on pedigree relationships. Correlation between pedigree distance and molecular Rogers' distance was significant (r = 0.77, P < 0.001). Based on these results, classification by molecular distance was convenient (i) for identifying heterotic groups and (ii) for assigning origins to unknown or broadly based inbreds. This information should prove useful for choosing (i) combinations of inbreds to be evaluated in hybrid trials and (ii) parents for breeding programs.