Gametocidal genes in wheat and its relatives. IV. Functional relationships between six gametocidal genes.

Gametocidal (Gc) genes in Aegilops species are known to cause gamete abortion and chromosome breakage when they are introduced into the wheat genetic background. Interactions of five Gc genes so far identified were investigated by analysis of wheat hybrids among lines carrying different gametocidal genes. As a result, the genes were classified into three functional groups. The first group includes two Gc genes of Ae. speltoides (Gc1a and Gc1b) and one gene (Gc-Sl3) on chromosome 2S1 of Ae. sharonensis. These genes were hypostatic to the genes (Gc-Sl1, Gc-Sl2) on chromosome 4S1 of Ae. longissima and Ae. sharonensis, which constitute the second group. In addition, plants carrying Gc genes of both the first and the second group produced progeny with higher frequencies of chromosome breakage than those found in the progeny of single gene carriers. It was concluded that there were specific interactions between these genes to enhance chromosome breakage. On the other hand, there was no interaction between the Gc gene (Gc-C) of Ae. triuncialis, the third group, and Gc genes belonging to the former two groups. These functional groups might be a reflection of the mechanisms by which Gc genes induce gamete abortion and chromosome breakage. Based on functional and local relationships, the symbols of the Gc genes were systematically redesignated.