Introgression of powdery mildew resistance from Aegilops triuncialis into wheat through induced homeologous pairing

Powdery mildew is a serious fungal disease of wheat caused by Blumeria graminis f. sp. tritici. Chromosome 5U of Aegilops triuncialis carrying powdery mildew resistance was induced to recombine with chromosome 5A of wheat using ph1b deletion line. The resulting recombinant progeny lines were tested for resistance and screened with molecular markers. Among 367 progeny lines 8 were immune to powdery mildew, 53 were moderately resistant, 231 moderately susceptible and 75 highly susceptible. Screening of 5U/5A recombinant lines with 5A specific SSR markers indicated that a major powdery mildew resistance gene from A. triuncialis was introgressed on the long arm of wheat chromosome 5A, along with two other loci, one located in the terminal end of the same arm and the other on the short arm of 5A. Meiotic metaphase-I pairing indicated that chromosome pairing in the resistant recombinant lines was regular with 21 bivalents and high seed set. The DNA markers associated with the introgressions can be used in marker assisted selection for improved powdery mildew resistance in wheat.