|Lee, Michael - ISU|
|Woodman, Wendy - ISU|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 4, 1996
Publication Date: N/A
Technical Abstract: The maize (Zea mays L.) populations Iowa Stiff Stalk Synthetic (BSSS) and Iowa Corn Borer Synthetic #1 (BSCB1) have undergone 12 cycles of reciprocal recurrent selection. An evaluation of molecular genetic changes in the populations will aid in understanding the continuing success of this program and may also suggest methods for improvements in this or other programs. This study focuses on molecular genetic variation in BSSS(R) and BSCB1(R) cycle 0 (CO) and cycle 12 (C12) populations, as well as their inbred progenitors (P). Multilocus genotypic data for 82 restriction fragment length polymorphism (RFLP) loci were collected from 100 randomly sampled individuals from each CO and C12 population, 16 BSSS(R) progenitors, and 12 BSCB1(R) progenitors. Progenitor lines were highly homozygous as expected. No single progenitor seems to have made excessive genetic contributions to CO or C12. The BSSS and BSCB1 progenitors were initially genetically similar (Nei's genetic distance = 0.07), but have had substantially diverged (Nei's distance = 0.66) after 12 cycles of selection. The genetic base across progenitor populations was very broad (mean gene diversity = 0.6) and continues to be so at C12 (0.6). Within both populations, polymorphism has decreased from about 99% to 75%, and gene diversity has decreased from about 0.6 to 0.3 between P and C12. The mean number of alleles has dropped from about four to less than three. The observed loss of variation is consistent with theoretical expectations resulting from genetic drift of neutral alleles.