PREFERENTIAL PAIRING OF CHROMOSOMES IN A TETRAPLOID HYBRID BETWEENORYZA GLABERRIMAANDO.SATIVA

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Abstract
A tetraploid hybrid was obtained from a cross between induced tetraploid strains of Oryza sativa L. and O. glaberrima Steud., which differed in glutinous (waxy) vs. non-glutinous starch (gl: +) and other genes. In the hybrid, as compared with the parental strains, there was a reduced number of quadricvalents and a relatively high degree of fertility. Segregation ratios for the glutinous gene observed in the back-cross and F2generation appeared to be modified not only by preferential homogenetic pairing but also by gametic selection. Taking into account the effect of gametic selection estimated from simplex heterozygotes, it was suggested that preferential pairing could take place to a certain extent. It seems to be difficult to measure quantitatively the degree of preferential pairing in tetraploid species hybrids, unless the effect of various segregation-distorting factors can be accounted for.