A Classification of 148 U.S. Maize Inbreds: I. Cluster Analysis Based on RFLPs
- Rita Hogan Mumm and
- J. W. Dudley
Knowledge of relationships among lines is essential to the maize (Zea mays L.) breeder because it directs the exploitation of germplasm in hybrid production. Restriction fragment length polymorphism (RFLP) data should be useful for estimating relationships among inbreds because they reflect differences in the DNA sequence. Cluster analysis, based on RFLPs resulting from 46 probe-enzyme combinations, was used to reveal associations among 148 U.S. maize inbreds and assign inbreds to heterotic groups. Estimates of genetic relationship between all pairs of inbreds were computed by Gower's Coefficient of Similarity and expressed as Euclidean distances. Then, these estimates were used to assign inbreds to groups by the average linkage method (UPGMA). Differences in the hybridization fragments exhibited lines within and between groups were evaluated to explore the basis for partitioning the fines. In the cluster analysis, inbreds were ordered into two major groups generally coinciding with distinctions between breeding groups derived from ‘Lancaster Sure Crop’ open pollinated variety and from Iowa Stiff Stalk Synthetic. Within these two groups, 11 subgroups were formed, each containing lines associated with an elite inbred (WF9, MO17, C103, PA91, OH43, T8, B14, B73, N28, B37, or OH07). The classification generally agreed with pedigree information and was supported by principal component analysis. Groups differed markedly in the proportions of lines exhibiting particular fragments. However, differences between groups reflected differences in frequencies rather than distinctions between the presence or absence of fragments by the vast majority of the lines in the respective groups.
Copyright © 1994.