New resistance genes for leaf rust and powdery mildew derived from T. turgidum ssp. dicoccum

Abstract

The tetraploid wheat relative Triticum turgidum ssp. dicoccum shows particular promises as a donor of useful genetic variation for several traits including disease resistances to be introgressed in cultivated wheat. The accession MG5323 of ssp. dicoccum, which showed useful level of resistance to leaf rust and powdery mildew diseases, was crossed with the susceptible durum wheat cultivar Latino. A total of 110 recombinant inbred lines (RILs) were produced and a high resolution linkage map was developed based on the 90K Infinium (Illumina). The parents and RIL population were phenotyped using two Puccinia triticina (VMC03 and 12766) and one Blumeria graminis (O2) isolates. Quantitative trait loci (QTL) analysis led to the identification of one major resistance gene conferring resistance to leaf rust on the short arm of chromosome 1B, explaining a total phenotypic variation ranging from 41.4 to 49.5%. Two additional minor resistance genes located on chromosome 7B explained a phenotypic variation ranging between 17.8 and 25.8%. For both QTLs the resistant allele was provided by MG5323. A significant positive epistatic effect was detected between QTLs , indicating that different QTLs contribute different degrees of resistance. Moreover, analys is of the leaf rust responses of the RILs demonstrated complementary actions between genes on chromosomes 1B and 7B. Analysis of powdery mildew resistance identified a single dominant gene on the short arm of chromosome 2B explaining 78.7% of total phenotypic variation. MG5323 provided the resistant allele at the QTL. A fine mapping approach of the major genes for both diseases was undertaken by developing a large F2-based high resolution mapping population and the flanking and peak markers were used to select a number of recombinant lines that are currently under phenotypic evaluation. The closest linked markers have been converted into PCR-based markers and are suitable for marker assisted selection (MAS) in resistance breeding.