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ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #81457
Title: TEMPORAL CHANGES IN ALLELE FREQUENCIES IN TWO DIRECTIONALLY SELECTED MAIZE POPULATIONS

Author
item LABATE, JOANNE
item LAMKEY, KENDALL
item LEE, MICHAEL - IOWA STATE UNIVERSITY
item WOODMAN, WENDY - IOWA STATE UNIVERSITY

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Commercially grown corn uses the hybrid method of production, that is, plants of high quality are produced from two parent plants that are not closely related. Several other important crops, such as tomato, are also bred this way. Using two types of corn which are being selected together to produce better hybrids, we are studying the genetics of the hybrids obtained from crossing them. This will help us to understand in general why certain pairs of strains produce better hybrids than others. We obtained genetic data from several-hundred plants representing strains both before and after selection. The changes in the genes in the two strains were compared. We found that both strains have changed during selection, and that the genetic changes were different and complemented each other. These findings are of interest to breeders of hybrid plants and animals. The study explains how to discover which genetic changes result in superior rhybrids. It also increases our understanding of how many genes are involved in improving corn hybrids.

Technical Abstract: We have examined allele frequency changes at 82 restriction fragment length polymorphism (RFLP) loci in two maize populations undergoing reciprocal recurrent selection (RRS), Iowa Stiff Stalk Synthetic (BSSS) and Iowa Corn Borer Synthetic #1 (BSCB1). After 12 cycles of selection approximately 30% of the alleles had gone extinct and 10% were near fixation in each population. Mean expected heterozygosity within the two subpopulations decreased 39%, and the between population component of genetic variation, D12, increased from 0.5% to 33.4% of the total. The LEWONTIN-KRAKAUER variance ratio test did not reject a neutral model of allele frequency change across all loci, but WAPLES' test identified several loci in each population whose allele frequency change cannot be explained by drift alone. Estimates of effective population size for each population fell within the range predicted by the breeding method.