Segregation distortion via male gametes in hybrids between Indica and Japonica or wide-compatibility varieties of rice (Oryza sativa L).

One or two marker genes on each of chromosomes 3, 4, 6, 7, 8, 11 and 12 of the 12 rice chromosomes were tested for segregation distortion in indica-japonica hybrids. Marker genes on chromosomes 3, 7, 8, 11 and 12 showed clear segregation distortion. This distortion was not related to the proportion of normal pollen. The germinability of the pollen was less than 10% in the hybrids, although 45-55% of the pollen grains appeared to be morphologically normal. The frequent occurrence of segregation distortion and the low germinability of the pollen grains suggested that a large portion of the pollen produced by the Indica-Japonica hybrids was not functional. The fact that the segregation distortion of the same marker may be positive or negative depending on the cross combination suggested the existence of multiple alleles, including distortion-neutral alleles. The latter mitigate pollen sterility in certain hybrid combinations.