Abstract
Chromosome pairing in MI of the PMC's was studied using the F1 hybrids between alloplasmic lines of a common wheat, Triticum aestivum cv. Chinese Spring (genome constitution AABBDD) as the female and rye (RR) or hexaploid triticale (AABBRR) in order to determine the effect of alien cytoplasms on meiotic chromosome behavior. The hybrids were obtained by embryo culture. Chromosome pairing in the hybrids of the first cross combinations (genome constitution ABDR) was entirely ascribable to the pairing between the homoeologues, whereas that in the hybrids of the second cross combinations (AABBDR) was due to both the homologous and homoeologous chromosome pairing. A D2 cytoplasm of Ae. crassa 4x promoted the homoeologous pairing but inhibited the homologous pairing. The S1 cytoplasm of Ae. sharonensis, another D2 cytoplasm of Ae. juvenalis, a G cytoplasm of T. timopheevi and an Sv cytoplasm of Ae. variabilis promoted whereas the Sb cytoplasm of Ae. bicornis inhibited the homoeologous pairing. Another Sv cytoplasm of Ae. kotschyi inhibited both the homoeologous and homologous pairing. The alloplasmic F1 hybrids from the first cross-combinations were crossed to an octoploid triticale (AABBDDRR) and the offspring were examined for their somatic chromosome number to estimate the effect of alien cytoplasms on the production of unreduced female gametes by the F1 's. Although the effect of individual alien cytoplasms could not be confirmed because of very low success in this cross, the overall frequency of the functional, unreduced gametes was estimated to be about 33%. Male-sterile octoploid triticales hav-ing the G-, Sv-, D2-and M-type cytoplasms were obtained for the first time by these crosses. Three alloplasmic octoploid triticale lines having D2-type cytoplasms showed photoperiod-sensitive cytoplasmic male sterility.
