Identification and mapping of quantitative trait loci for leafudrust resistance derived from a tetraploid wheat Triticumuddicoccum accession

摘要

The Triticum turgidum ssp. dicoccumud(2n = 4x = 28) accession MG5323 showed a usefuludlevel of resistance to leaf rust disease. A segregatingudpopulation of 110 recombinant inbred lines (RILs),udderived from a cross between cv Latino (T. turgidumudspp. durum), susceptible to leaf rust, and MG5323 wasudevaluated for reactions of seedlings to two differentudPuccinia triticina isolates. Genotyping of the RILsudwas performed with different molecular markersud(SSR, EST-SSR and SNP), leading to the constructionudof a linkage map containing 10,840 loci covering 14udchromosomes, with an average marker density ofud0.22 cM/marker. Linkage analysis allowed the identificationudof three different regions significantly associatedudwith leaf rust resistance, with MG5323udcontributing the resistant alleles. A major resistanceudgene was detected on the short arm of chromosomeud1B, explaining a total phenotypic variation rangingudfrom 41.37 to 49.51 %. Two additional minor resistanceudgenes located on chromosome 7B explained audphenotypic variation ranging between 17.77 andud25.81 %. No obvious positional relationships wereudobserved when the map position of the genes wasudcompared with those of other previously identifiedudwheat leaf rust resistance genes, suggesting that newudresistance sources to leaf rust were identified in theudtetraploid background. A significant positive epistaticudeffect was detected between quantitative trait lociud(QTLs) for each trait, indicating that different QTLsudcontribute different degrees of resistance. Analysis ofudthe leaf rust responses of the RILs demonstrated thatudonly lines bearing resistant alleles at both loci showedudeffective leaf rust resistance, indicating that the genesudidentified behave as complementary genes.