EXPECTED LEVELS OF HETEROZYGOSITY IN AUTOTETRAPLOID PROGENY POPULATIONS

The level of heterozygosity at multi-allelic loci is related to vigor in autotetraploid forage species. Increasing the proportions of tri- and tetra-allelic individuals in the commercial seed generation is one approach for improving yield. In this study, computer simulation was used to determine the expected genotypic structures of progeny populations from various mating designs. Four- and 8-allele models were examined. The proportion of tetra-allelics declined rapidly as synthetics derived from non-inbred clones were advanced from the Syn-1 to the Syn-3 generation. In multi-clone synthetics from partially inbred parents, the frequency of tetra-allelics increased with generation advance, but never reached the levels obtained with non-inbred parents. The frequencies of tetra-allelics in populations crosses between mutually heterotic parents was higher than in conventional synthetics provided that pollination occurred only between the parental populations. With random pollination within and between parents, progenies were less heterozygous than conventional synthetics.