Genetic Variability Within U.S. Maize Germplasm. I. Historically Important Lines1

Abstract

Isozyme data for 21 loci from 72 historically important U.S. Corn Belt and southern lines of maize (Zea mays L.) were analyzed by principal component analysis. The objectives were to compare relationships with those to be expected from known pedigrees and to discuss the information revealed by isozyme data with regard to the utilization of elite germplasm. Considerable genetic diversity was found, especially among ‘Reid Yellow Dent’ and ‘Iowa’ Stiff Stalk Synthetic' lines. Several isozyme differences were apparent between Corn Belt and southern lines. Isozyme data tended to group lines of similar background together although tight clustering of related lines was not found. Iowa Stiff Stalk Synthetic lines showed little or no relationship to ‘Lancaster Sure Crop’, ‘Minnesota 13’, or ‘Midland’ lines, but they did appear to be a blend of Reid Yellow Dent and non‐Reid Yellow Dent germplasm. The germplasm base of U.S. maize appeared broader than would have been expected solely on the basis of the numbers of races involved in its origins. The most successful sources of elite germplasm each encompassed a broad range of genetic diversity.