Variation in the distribution of a genome-specific DNA sequence on chromosomes reveals evolutionary relationships in the Triticum and Aegilops complex

Abstract.

 The present study analyzed the distribution pattern of the Ae. speltoides–derived repetitive clone pGc1R-1 in the Triticum/Aegilops complex. Fluorescence in situ hybridization analysis showed that clone pGc1R-1 is a S-genome-specific repetitive sequence that hybridized to the S-genome of three species in the section Sitopsis, Aegilops speltoides (S), Ae. longissima (S^l), and Ae. sharonensis (S^sh), but not to Ae. bicornis (S^b) and Ae. searsii (S^s), nor to any other diploid Aegilops species. This clone also hybridized to the very closely related G-genome of T. timopheevii subsp. armeniacum and T. timopheevii ssp. timopheevii, but not to the B-genome of T. turgidum and T. aestivum. Hybridization also was observed in the polyploid Aegilops species, Ae. kotschyi (U^kS^k), Ae. peregrina (U^pS^p), and Ae. vavilovii (X^vaD^vaS^va). Large inter- and intraspecific variations were observed. Our results confirm that the S genome is related more to the S^l and S^sh genomes than to the S^b and S^s genomes; there is a greater affinity between the G and S genomes than between the B and S genomes. Mechanisms to account for the variation in the FISH pattern with different genomes include sequence amplification and deletion. Variation in the distribution of this genome-specific DNA sequence, pGc1R-1, on chromosomes can be used to reveal evolutionary relationships in the Triticum and Aegilops complex.