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 significa nt heterotic groups (i.e., European flint, Lancaster Sure Crop, Minnes ota 13, and Reid Yellow Dent) and miscellaneous origins were assayed f or 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 miscellan eous lines to heterotic groups by means of probes selected for lotus s pecificity, clear patterns, and reproducibility. Among the 63 single c opy probe-enzyme combinations used, 372 variants were scored with a me an of 5.9 variants per combination. Principal component and cluster an alyses performed on lines from established heterotic groups clearly se parated hint lines from dent lines. Loci that contributed the most to the genetic differentiation between European flint and northern U.S. d ent lines were determined. Within U.S. germplasm, classification showe d an association of inbreds that closely matched associations based on pedigree relationships. Correlation between pedigree distance and mol ecular Rogers' distance was significant (r = 0.77, P < 0.001). Based o n 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 tr ials and (ii) parents for breeding programs.