ISOLATION, CHARACTERIZATION AND APPLICATION OF A SPECIES-SPECIFIC REPEATED SEQUENCE FROM HAYNALDIA-VILLOSA

A species-specific repeated sequence, pHvN-AU62, was cloned from Hayna ldia villosa, a wheat relative of great importance. It strongly hybrid ized to H. villosa, but not to wheat. In situ hybridization localized this sequence to six of seven H. villosa chromosome pairs in telomeric or sub-telomeric regions. Southern hybridization to wheat-H. villosa addition lines showed that chromosomes 1V through 6V gave strong signa ls in ladders while chromosome 7V escaped detection. In addition to H. villosa, several Triticeae species were identified for a high abundan ce of the pHvN-AU62 repeated sequence, among which Thinopyrum bassarab icum and Leymus racemosus produced the strongest signals. Sequence ana lysis indicated that the cloned fragment was 292 bp long, being AT ric h (61%), and showed 67% homology of pSc7235, a rye repeated sequence. Isochizomer analysis suggested that the present repeated sequence was heavily methylated at the cytosine of the CpG dimer in the genome of H . villosa. It was also demonstrated that pHvN-AU62 is useful in taggin g the introduced 6VS chromosome arm, which confers a resistance gene t o wheat powdery mildew, in the segregating generations.