Karyological Studies in Haploid Rice Plants

Abstract

Haploid plants were obtained from a twin seedling of a strain of O. glaberrima. The karyotype of the plants was investigated first using root tip cells. Nine types of chromosomes could be distinguished by their size, position of constriction, and presence or absence of satellite and secondary constriction. The karyotype of O. glaberrima was thus found to be identical with that of O. sativa, formerly observed by the writer.Secondly, meiosis in PMCs was investigated with regard to intra-genome pairings of chromosomes. Seemingly true pairings to form bivalents and trivalents, and assemblies of two or three univalents which appeared to be due to secondary assoociation, could be distinguished. The frequency distribution of cells with different numbers of pairings was similar to that found in haploid plants of O. sativa, and the maximum pairing found was five groups of chromosomes.These observations lead to the conclusion that O. glaberrima might have structurally the same chromosomes as those of O. sativa, and these two species might have arisen from a common ancestral plant.