Nonrandom association of genes and characters found in indica X japonica hybrids of rice

Abstract

Two subspecies of common rice, indica and japonica, are distinguishable by differences in alleles at a number of loci controlling biochemical and morphological traits. The nature of associations between twelve alleles and phenotypes was studied in both a sample of varieties and hybrid populations derived from a single indica × japonica cross. Many of the associations found in varieties were not found in the F2 population. The nine sets of associations observed in F2 are explained by linkage. However, seven nonrandom associations were recovered in an Fs population, derived in such a way as to minimize the effect of zygotic selection, which were not found in F2. The genes involved in these associations were not genetically linked and young zygotes showed no differences in fitness between parental and recombined genotypes. These results suggest that increasing parental association of genes and characters in a hybrid population is most probably caused by gametic selection. This gametic selection could be a causal factor promoting the indica-japonica differentiation in rice varieties. © 1990 The Genetical Society of Great Britain.