Repeatability and heritability of divergent recombination frequencies in the Iowa Stiff Stalk Synthetic (Zea mays L.)

Variability in recombination frequency was reported in the Iowa Stiff Stalk Synthetic. The objectives of the present research were to verify the differences in recombination frequency among individuals in the Iowa Stiff Stalk Synthetic maize population and to determine if the recombination frequency differences persisted among the S₁ progeny. Testcrosses to measure male recombination frequency on three chromosomes (4, su1-c2; 5, a2-bt1-pr1; 9, sh1-bz1-wx1) were repeated for eight S₀ individuals. Recombination frequencies were repeatably divergent among those individuals which were selected based on high or low recombination frequencies on specific chromosomes. Individuals which had been selected for long and short total map distances across the three chromosome regions produced repeatably divergent recombination frequencies only at the su1-c2 region. The recombination frequencies of the S₁ lines, derived from the S₀ individuals which had the most divergent recombination frequencies on a single chromosome, were significantly different. The broad-sense heritability estimates derived from the regression of six S₁ lines on six S₀ individuals ranged from 0.69 to 0.20 for the five chromosome regions. We conclude that genetic differences for recombination frequency exist in this population and that modification by selection should be possible.