Nonrandom association of genes and characters found in indica × 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 x 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 F5 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 indicajaponica differentiation in rice varieties.

Genetic Erosion from Modern Varieties into Traditional Upland Rice Cultivars (Oryza sativa L.) in Northern Thailand

“…Rarely they would be intermediate type as seen in this report. This phenomenon may explain by our previous data referred as non-random association of Indica-Japonica traits (Sato et al 1990). Wild relatives also face the risk of hybridization with modern varieties.…”

Non-random distribution of the alleles for good grain filling at OsAGPS2 and OsSUT1 among a wide range of rice (Oryza sativa L.) cultivars

“…Although the mechanisms underlying such non-random distribution of these alleles remains to be resolved, artificial and/or natural selection, including gametic and zygotic selection, in the course of cultivar development might contribute to these results. Sato et al (1990) and Morishima (2001) reported that such gene associations were frequently found in the course of domestication and differentiation in rice. The selective advantage of the genotypes, AS2-2 SUT1-2 and also AS2-1 SUT1-1, in the past development of indica cultivars should be clarified to obtain further information for future rice breeding programs.…”

Association of esterase isozymes with morphology in F2 progenies of two growth variants in Poa annua L.

“…The indica-japonica differentiation is caused by multilocus associations. A few associations were due to linkage and easily maintained by natural or artificial selection, but most were lost in Fĝ enerations of indica x japonica hybrids (Sato, Ishikawa & Morishima, 1990). …”