REPEATABILITY AND HERITABILITY OF DIVERGENT RECOMBINATION FREQUENCIESIN THE IOWA STIFF STALK SYNTHETIC (ZEA-MAYS L)

Variability in recombination frequency was re parted in the Iowa Stiff Stalk Synthetic. The objectives of the present research were to verif y the differences in recombination frequency among individuals in the Iowa Stiff Stalk Synthetic maize population and to determine if the re combination frequency differences persisted among the S-1 progeny. Tes tcrosses to measure male recombination frequency on three chromosomes (4, sul-c2; 5, a2-bt1-pr1; 9, sh1-bz1-wx1) were repeated for eight So individuals. Recombination frequencies were repeatably divergent among those individuals which were selected based on high or low recombinat ion frequencies on specific chromosomes. Individuals which had been se lected for long and short total map distances across the three chromos ome regions produced repeatably divergent recombination frequencies on ly at the sul-c2 region. The recombination frequencies of the S-1 line s, derived from the S-0 individuals which had the most divergent recom bination frequencies on a single chromosome, were significantly differ ent. The broad-sense heritability estimates derived from the regressio n of six S-1 lines on six S-0 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 modificatio n by selection should be possible.