Identification and mapping of leaf rust and powdery mildew resistance genes derived from T. turgidum ssp. dicoccum.

The tetraploid wheat Triticum turgidum ssp. dicoccum shows particular promises as a donor of useful genetic variation for several traits including disease resistances to introgress in cultivated wheats. The accession MG5323 of ssp. dicoccum, resistant to powdery mildew and leaf rust, was crossed to susceptible durum wheat cultivar Latino and a set of 113 recombinant inbred lines (RILs) was produced. The objective of this work was to identify and map leaf rust and powdery mildew resistance loci from dicoccum accession. The parents and RIL population were phenotyped, under controlled greenhouse conditions, with two Puccinia triticina (VMC03 and 12766) and one Blumeria graminis (O2) isolates. Marker analysis of the RILs was performed using a large set of different molecular markers (SSR, EST-SSR,COS and SNP) leading to the construction of a linkage map containing 7,808 polymorphic loci covering 6,228 cM of genetic distance on the fourteen chromosomes of durum wheat, with an average distance of 0.80 cM between adjacent markers. Linkage analysis allowed the identification of different regions significantly associated with leaf rust and powdery mildew resistances. One major gene conferring resistance to leaf rust was detected on the short arm of chromosome 1B, explaining a total phenotypic variation ranging from 41.89 to 52.56% and an additional minor gene was located on chromosome 7B, explaining 12.16-31.24% of total phenotypic variation. About the powdery mildew resistance a single dominant gene was located on the short arm of chromosome 2B explaining 67.90% of total phenotypic variation. These results allowed the identification of new resistance genes to leaf rust and powdery mildew in a tetrapoid wheat genetic background and the closest linked markers identified can be used for marker-assisted selection (MAS) making feasible the development of resistant durum wheat cultivars using the discovered resistance genes.