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United States Department of Agriculture

Agricultural Research Service

Title: Isozyme Allelic Frequency Changes Following Maize (Zea Mays L.) Germplasm Regeneration

Authors
item Reedy, M - ISU
item Knapp, Allen - ISU
item Lamkey, Kendall

Submitted to: Maydica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 1995
Publication Date: N/A

Interpretive Summary: Germplasm collections serve the function of preserving genetic diversity. In order for germplasm collections to be effective, genetic diversity of collections must be maintained for long periods of time. The long term maintenance of germplasm requires periodic renewal of seed generally by hand crossing. The number of plants hand crossed has a direct effect on the loss of genetic diversity within a collection. Biochemical genetic markers were used to examine how genetic diversity has changed in several corn germplasm collections when compared with the original collection. There was no evidence of selection during regeneration of the corn germplasm. In addition there seemed to be little evidence of random changes in marker frequencies due to chance, suggesting that regeneration protocols are adequate. These results will be of interest to both corn breeders as well as germplasm curators.

Technical Abstract: Germplasm collections serve the essential function of preserving genetic diversity. Genetic drift, the erratic, random fluctuation in gene frequency that can result from inadequate sampling during periodic regeneration of accessions, and selection have the potential to change the genetic identity of germplasm collections. Random genetic drift may lead to either fixation or loss of alleles. Small numbers of parents used in early regeneration cycles may reduce variability from that present in the original population. The degree of diversity in five maize germplasm accessions was measured as a function of isozyme polymorphism and allelic frequencies were examined following several cycles of regeneration. A statistical procedure was used to test whether observed allele-frequency variation from cycle to cycle of regeneration was consistent with a hypothesis of drift acting alone or if a linear trend indicated possible selection. The results indicated that most of the fluctuation observed in allelic frequencies can be attributed to random genetic drift. Alleles present in low frequencies were not represented in each cycle of regeneration as a result of sampling error.

Last Modified: 12/27/2014
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