NUCLEOCYTOPLASMIC INTERACTIONS STABILIZE PLOIDY LEVEL IN WHEAT INTERSPECIFIC HYBRIDS

The cytoplasm of Aegilops squarrosa L. (2n = 14; DD) is compatible with the nuclei of Triticum aestivum L. (2n = 42; AABBDD) and the pentaploid F1 (2x = 35; AABBD), but not with the euploid nucleus of Triticum turgidum L. (2n = 28; AABB). To identify D-genome chromosomes with the genes conditioning differential nucleocytoplasmic compatibility, ae and sq 5x F1, having cytoplasms of T. aestivum and Ae. squarrosa, respectively, were reciprocally crossed to the seven doubled ditelosomics (d-dts) of the D-genome chromosomes (including four control crosses of d-dts 1A, 1B, and sq 5x F1). The 32 progeny were examined for the presence or absence of unpaired telosomes, monosomes, and the maximum number of bivalents at the meiotic metaphase I in the pollen mother cells for comparison with the transmission of ae and sq male and ae and sq female gametes carrying different numbers of D-genome chromosomes. The sq gametes with 1D, 5D, and other D-genome chromosomes had a strong functional advantage. In contrast, the ae gametes with 1D and other D genome chromosomes, except 5D, had a functional disadvantage. The sq and ae 5x F1 transmitted chromosome 5D through 80.0 and 72.2% of the male and 58.6 and 44.8% of the female gametes, respectively. We concluded that the sq gametes tended to increase and ae gametes tended to reduce the ploidy levels of the progeny.