A GAMETE ABORTION LOCUS DETECTED BY SEGREGATION DISTORTION OF ISOZYMELOCUS EST-9 IN WIDE CROSSES OF RICE (ORYZA-SATIVA L)

A locus for male gamete abortion in hybrids for Japonica and Indica ri ce was identified with the aid of marker genes Rc and Est-9 on chromos ome 7. In an Indica-Japonica cross, AKAMAI 1/IR50, the Indica allele E st-9(2) was transmitted via the male gamete with a ratio of 0.29 inste ad of the normal 0.5, whereas no segregation distortion was observed f or the Rc locus. The recombination value (p) for Est-9 and Rc was esti mated to be 0.38 by a least square method after adjusting Mendelian se gregation ratios with the male transmission ratios of 0.29 (Tr) for Es t-9(2) and 0.71 (1-Tr) for Est-9. The recombination value (q) for the new locus for male gamete abortion, ga-11, and Est-9 was estimated to be 0.23 by using 56 F3 lines from F2 plants which were heterozygous fo r the Est-9 locus. No linkage for Rc and ga-11 was found. Therefore, t he two markers and ga-11 were located in the order of ga-11-Est-9-Rc. Using the estimated recombination value (q), the male transmission rat e (k) of ga-11a was estimated to be 0.11 with the F2 data and - 0.07 w ith the F3 line data. Thus, it was apparent that male gametes possessi ng ga-11a were frequently aborted in the Indica-Japonica hybrid.