A distorted segregation of high lysine gene Iys3a located in chromosome 7 was found in several crosses (Ahokas, 1979, 1988; Doll and Oram, 1989). Recently, Doll (1991) demonstrated that the distorted segregation of Iys3a gene was observed in the reciprocal backcrosses of 'Riso 1508' × 'White Naked Atlas', only when the hybrid was used as the male parent.

The objectives of the present study was to re-examine the above-mentioned result of Doll, and to estimate the linkage value between Iys3a and the factor for the segregation distortion, using the hybrids of Riso 1508 and 'Beecher' of which the seed samples of their parents were kindly presented from H. Doll and R. Oram, respectively.

Segregation of Iys3a mutant kernels in F₂ populations of the reciprocal crosses were examined (Table 1). Frequency of the mutant kernels decreased significantly compared with the theoretical one of 25%, and the frequency did not differ between the F₂ populations of the reciprocal crosses, suggesting that there was no effect of the parental cytoplasms on the segregation distortion.

Furthermore, segregation of the mutant kernels in B₁F₁ hybrids of the reciprocal backcrosses between Riso 1508 and Beecher was investigated (Table 2). When Riso 1508 was backcrossed with either of the reciprocal F₁ hybrids (R × B and B × R) as female parent, the segregation frequency of normal and mutant kernels fitted well to a ratio of 1:1 as expected in monogenic segregation. Meanwhile, when either of the reciprocal Fl hybrids were used as the male parent, the segregation was significantly distorted from the theoretical ratio (1:1).

For estimating the linkage value between Iys3a and a factor for the segregation distortion, segregation of the mutant kernels in each of the F₃ heterozygous progenies at the Iys3a locus was examined (Table 3). Out of 23 F₃ progenies examined, 20 progenies showed the distorted segegation, while 3 progenies exhibited the normal segregation. The linkage value was estimated to be 6.52 ± 0.04% by the formula proposed by Nakagahra (1972).

From these results, it is concluded that the segregation distortion is caused by the gametophyte gene designated as Ga3 different from Ga2 on chromosome 3 (Konishi et al., 1990), that pollen carrying Ga3 may have no ability for pollination, since the pollinating ability (K) was calculated to be 0.0102 by the formula of Nakgahra (1972).

Ahokas, H. 1979. Further results on the suppression of shrunken endosperm in high lysine mutants. BGN 9:3-7.

Ahokas, H. 1988. High-lysine gene segregation distorted in the barley cross Riso 1508 × Crypt CI 1090: Patterns of endosperm proteins by an electrophoretic method. Hereditas 108:129131.

Doll, H. 1991. A factor on barley chromosome 7 causing distorted male segregation of gene Iys3a. BGN 20:23-24.

Doll, H., and R. Oram. 1989. Deviating Mendelian segregation of barley gene Iys3a. Hereditas 110:97-99.

Konishi, T., K. Abe, S. Matuura, and Y. Yano. 1990. Distorted segregation of the esterase isozyme genotypes in barley (Hordeum vulgare L.). Jpn. J. Genet. 65:411-416.

Nakagahra, M. 1972. Genetic mechanism on the distorted segregation of marker genes belonging to the eleventh linkage group in cultivated rice. Japan. J. Breed. 22:232-238.