Identification of molecular markers linked to PM13, an Aegilops longissima gene conferring resistance to powdery mildew in wheat

RFLP, RAPD, STS and DDRT-PCR techniques were applied to find molecular markers linked to Pm13, an Aegilops longissima gene conferring resistance to powdery mildew in wheat. The experimental strategy was based on the differential comparison of DNAs from common wheat and from common wheat/Ae. longissima recombinant lines carrying short segments of the 3S(l)S chromosome arm containing the Pm13 gene. Sixteen RFLP clones that detect loci previously located in the short arms of group-3 wheat chromosomes were screened for their ability to hybridise to Ae. longissima restriction fragments derived from the 3S(l)S segments introgressed into the recombinant lines. Eight RFLP clones and one STS marker detected 3S(l)S-specific fragments whose location relative to the wheat-alien chromatin breakage point of the recombinant lines was determined. Four amplification products were identified through the screening of about 200 RAPD primers. Their polymorphism was associated with the introgression of the alien DNA. One of the differential fragments was derived from the 3S(l)S DNA segment, while the remaining three corresponded to the replaced 3DS DNA. Further analyses carried out using 40 combinations of DDRT-PCR primers detected an additional reproducible polymorphism associated with the presence of 3S(l)S DNA. In view of their possible utilisation in Pm13 marker-assisted selection, differentially amplified RAPD and DDRT-PCR fragments were cloned, transformed into RFLP markers and converted into STS markers.