| ROBERTSON and CURTIS (1967) investigated by the same method a hexaploid
strain from the cross, T. timopheevi x T. aestivum cultivar
Marquis3, that is another fertility-restorer to the timopheevi
cytoplasm, and reported that it carried one of the duplicated fertility-restoring
genes, Rf1, on chromosome 1A, while the other gene, Rf2,
could not be located, whose location was lately identified in chromosome
7D (MAAN, unpublished). We found here that T. spelta var. duhamelianum
carries a single dominant fertility-restoring gene on its chromosome 1B;
this gene will be designated as Rf3. It is noteworthy
that Rf1 and Rf3 are located on homoeologous
chromosomes, 1A and 1B. These findings can be utilized to increase the dosage
of restoring genes in a restorer line to get the maximum seed fertility
in the F1 hybrid wheat. As to the role of chromosome 7D in fertility-restoration, results of two previous works must be mentioned. MAAN and LUCKEN (1968) reported that Chinese Spring mono-7D with the timopheevi cytoplasm was somewhat fertile, while disomic Chinese Spring with the same cytoplasm was mostly sterile. Their result suggests that chromosome 7D of Chinese Spring carries a weak fertility suppressor, whose hemizygous condition causes some fertility restoration. As mentioned above, a hexaploid derivative of the cross, T. timopheevi x Marquis3, received two restoring genes from T. timopheevi, one of which (Rf2) was located on chromosome 7D (MAAN, unpublished). His explanation of the result is, however, hard to accept because a gene of T. timopheevi can be rarely transferred to a D-genome chromosome. On the contrary, presence of a weak suppressor in chromosome 7D of Marquis, as in Chinese Spring, may explain his result without any complication. From these considerations, we may assume a stronger suppressor in chromosome 7D of T. spelta var. duhamelianum than that of Chinese Spring or Marquis, in order to explain a distorted ratio of fertile vs. sterile plants in mono-7D family of the present experiment. (Received October 14, 1968) |
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