Restriction Fragment Length Polymorphism (RFLP) for protein disulfide isomerase (PDI) gene sequences in Triticum and Aegilops species

RFLP variation revealed by protein disulfide isomerase (PDI) coding gene se quences was assessed in 170 accessions belonging to 23 species of Triticum and Aegilops. PDI restriction fragments were highly conserved within each s pecies and confirmed that plant PDI is encoded either by single-copy sequen ces or by small gene families. The wheat PDI probe hybridized to single Eco RI or HindIII fragments in different diploid species and to one or two frag ments per genome in polyploids. Four Aegilops species in the Sitopsis secti on showed complex patterns and high levels of intraspecific variation, wher eas AE. searsii possessed single monomorphic fragments. T. urartu and Ae. s quarrosa showed fragments with the same mobility as those in the A and D ge nomes of Triticum polyploid species, respectively, whereas differences were observed between the hybridization patterns of T. monococcum and T. boeoti cum and that of the A genome. The single fragment detected in At. squarrosa was also conserved in most accessions of polyploid Aegilops species carryi ng the D genome. The five species of the Sitopsis section showed variation for the PDI hybridization fragments and differed from those of the B and G genomes of emmer and timopheevi groups of wheat, although one of the Ae. sp eltoides EcoRI fragments was similar to those located on the 4B and 4G chro mosomes. The similarity between the EcoRI fragment located on the 1B chromo some of common and emmer wheats and one with a lower hybridization intensit y in Ae. longissima. Ae. bicornis and Ae. sharonensis support the hypothesi s of a polyphyletic origin of the B genome.