A diagnostic analysis of genetic differentiation among subpopulations of a barley composite cross using isozyme markers
Zhang, Q., S. Jana and M. A. Saghai Maroof. 1993. Hereditas 118:63-70.
ABSTRACT We previously observed strikingly different multivariate complexes in three subpopulations of barley Composite Cross XXI (CCXXI) grown simultaneously at three North American locations for many generations. In this paper, we report on our diagnostic analyses of some basic features of genetic differentiation in CCXXI using data from seven enzyme loci which were divided into two subsets. Results of this study indicate that the striking differences observed in our previous study were due to significant geographical differentiation among subpopulations, and such that differentiation increased progressively as the generations advanced. The analyses reveal two contrasting patterns, as demonstrated by the two subsets of loci, in responding to the selection pressures associated with geographical differentiation. In the first subset of loci, responses occurred mainly at the level of individual loci; whereas in the second subset, joint responses of two or more loci played an important role in differentiation. Linkage disequilibria decreased at a faster rate than neutral decay in the first subset both within subpopulations and in the total population, but increased greatly in the second subset of loci. These results suggest that heavy inbreeding even when coupled with tight linkage did not necessarily hold the genotypes together in the processes of genetic differentiation.