Segregation distortion of genotypes, which consisted of allelic combinations at the complex loci, Estl, Est2, and Est4, for esterase isozymes, was observed in F2 population derived from a cross combination between 'Ko A' and 'Mokusekko 3'. It means that the Ga2 locus for the segregation distortion was linked with the complex loci (Konishi et al., 1990).
The parents, Ko A (Ga2), and Mokusekko 3 (ga2), and their reciprocal F1 plants were used for all possible backcross combinations. Segregation of the esterase isozyme genotypes in the B1F1 plants was examined by a starch gel electrophoretic method (Konishi et al., 1989), using the first leaf of each 10-day old seedling.
Table 1 indicates segregation of the esterase isozyme genotypes in B1F1 lants derived from reciprocal backcrosses between Ko A (KA) and Mokusekko 3 (MK). When the F1 plants were used as the female parent, segregation of genotypes of KA and F1 or MK and F1 fitted well to a ratio of 1:1. However, when the F1 plants were used as the male parent, the segregation was distorted. These results indicated that the segregation distortion appeared only when the F1 plants were used as the male parent.
Furthermore, as the segregation distortion might be caused by certation, which means competition in growth rate between pollen tubes of different genes at the Ga2 locus, a single pollen grain of the F1 plants was pollinated on each stigma. The single pollen grain pollination could prevent the certation.
Table 2 shows segregation of the esterase isozyme genotypes in B1F1 plants of which Mokusekko 3 was backcrossed with the reciprocal F1 plants by the single pollen grain pollination. The segregation was significantly deviated from a ratio of 1:1. These results were similar to those in the lower- column of Table 1 when the F1 plants were used as the male parent.
From these results, it may be concluded that the segregation distortion is caused by the gametic selection during the pollen production, not by the certation.
Konishi, T., K. Abe, S. Matsuura, and Y. Yano. 1990. Distorted segregation of the esterase isozyme genotypes in barley (Hordeum vulgare L.). Japan J. Genet. 65:411-416.
Konishi, T., N. Kawada, H. Yoshida, and K. Sohtome. 1989. Linkage relationship between two loci for the barley yellow mosaic resistance of Mokusekko 3 and esterase isozymes. Japan. J. Breed. 39:423-430.