Isozyme allele frequency changes during corn germplasm regeneration
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Germplasm collections serve the essential function of preserving genetic diversity for current and future use. Genetic drift, the erratic, random fluctuation in gene frequency which is a function of sampling error during periodic regeneration of accessions, and selection have the potential to change the genetic identity of germplasm accessions. There is some concern that the small numbers of parents used in early regeneration cycles may have reduced variability so that the accessions may not contain all of the variability present in the original population. The degree of diversity in five maize germplasm accessions as a function of isozyme polymorphism was determined and allelic frequencies examined following several cycles of regeneration. A statistical procedure was used to test whether the observed allelic frequency variation from cycle to cycle of regeneration was consistent with that predicted by the 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.