| Genome analysis of Aegilops mutica Boiss. and
its phylogenetic position in the genera Aegilops and Triticum
S. Ohta Plant Germ-plasm Institute, Faculty of Agriculture, Kyoto University, Mozume, Muko, Kyoto 617, Japan Introduction To estimate the genome relationship between Ae. mutica and the other diploid species of the genera Aegilops and Triticum by the chromosome pairing at MI of meiosis in their F1 hybrids, ten diploid Aegilops and a diploid Triticum species were crossed with Ae. mutica. Among the crosses the F1 hybrids were obtained from the crosses of nine Aegilops and a Triticum species x Ae. mutica. One of the difficulties in estimating the genome relationships among diploid species by the meiotic chromosome pairing in their F1 hybrids is that non-homologous but partially homologous or homoeologous chromosomes from the both parents pair with their counterparts. In the present work, B-chromosomes of Ae. mutica were used as a useful tool for suppressing such a homoeologous chromosome pairing. It is well known that they effectively suppress the frequency of the pairing between homoeologous chromosomes though they do not affect that between fully homologous ones. The simplified principle of the present genome analysis using B-chromosomes is shown in Fig. 1. Based on the chromosome pairing at MI in the F1 hybrids both with and without B-chromosomes between the diploid species and Ae. mutica, the genomes of the diploid species are classified into the following three classes according to the degree of their homology with the genome of Ae. mutica designated as Mt in Fig. 1: (a) the genome designated as X has no homology with the genome of Ae. mutica when chromosomes derived from the two parents do not pair at all and only 14 univalents of A-chromosomes are observed in the F1 hybrids both with two B-chromosomes (2B hybrids) and without B-chromosomes (0B hybrids); (b) the genome Y is partially homologous or homoeologous with that of Ae. mutica when the 0B hybrids show a very high frequency and an almost regular configuration of chromosome pairing as seven bivalents while the 2B hybrids show a drastically low frequency of chromosome pairing and form only 14 univalents of A-chromosomes; and (c) the genome Z is homologous with that of Ae. mutica when both the 0B and 2B hybrids show a very high frequency and a regular configuration of A-chromosome pairing. |
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