A SURVEY OF GENETIC VARIATIONS IN THE POPULATIONS OF WILD ORYZA SPECIES AND THEIR CULTIVATED RELATIVES

抄録

The first-generation plants raised from population seed samples belonging to Oryza perennis, O. sativa, O. breviligulata and O. glaberrima, each collected from its natural habitat or a farmer's field, were observed for various metric characters, and their intra-populational genetic variability was estimated for each character and also in terms of generalized variance. In O. perennis, perennial and allogamous forms generally contained in their populations more genetic variation than the annual and autogamous forms, while the latter tended to be more diversified from one another. The level of heterozygosity was estimated from the ratio of within-line to between-line component of genetic variance. Perennial and allogamous forms were more heterozygous than annual and autogamous ones. Diallel analysis of a perennis population showed appreciably large mean squares due to dominance for certain characters. Further, intra-populational variability in spikelet size was observed using the original seeds collected from various sites. Though cultivated forms (sativa and glaberrima) were largely homozygous, their populations in primitive agricultural conditions contained as much genetic variations as wild forms. This was considered to be due to introgression and disruptive selection in the environment.