Homoeologous pairing and recombination between the long arms of group 1 chromosomes in wheat × rye hybrids

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Abstract
The relationship between homoeologous pairing at metaphase I and recombination at anaphase I between the arms 1AL, 1BL, 1DL, and 1RL was analyzed in ph1b, 5B-deficient, and ph2b wheat × rye hybrids. All four arms could be identified at metaphase I, as well as the arms 1BL and 1RL at anaphase I, by means of C-banding. On the basis of the C-heterochromatin constitution that 1BL and 1RL showed at anaphase I and that association at metaphase I was essentially homoeologous, the following anaphase I chromosome types could be distinguished: parental type, single and double recombinant types between 1BL and 1AL or 1DL, between 1BL and 1RL, and between 1RL and 1AL or 1DL. Recombinant types 1AL – 1DL did not differ from the parental type for the C-banding pattern and was not considered. In the three genotypes, most if not all of 1BL – 1AL, 1BL – 1DL, and 1BL – 1RL metaphase I bonds were chiasmatic. 1RL – 1AL and 1RL – 1DL associations were scarce. Frequencies of one chiasma and two chiasmata for the arm combinations 1BL – 1AL plus 1BL – 1DL, 1BL – 1RL, and 1RL – 1AL plus 1RL – 1DL were estimated. Values decreased in the order ph1b, 5B-deficient, and ph2b hybrids.Key words: C-banding, chiasmata, homoeologues, anaphase I, ph genes.