QTLs associated with resistance to chlorosis induction by Pyrenophora tritici-repentis in adult wheat

The number of genes conditioning resistance in adult wheat plants to the induction of chlorosis by Pyrenophora tritici-repentis was estimated with molecular markers. Wheat plants from a segregating population of 112 recombinant inbred lines derived from the cross of the synthetic hexaploid W-7984 with Opata 85 were inoculated at anthesis with race 1 isolate Pti2. The inoculated flag leaves were rated on a scale of 1 to 5 based on infection type. An RFLP map consisting of 542 markers was employed to identify significant associations (P < 0.01) between marker loci and adult tan spot resistance. All of the markers were subjected to multiple regression analysis using the computer program qGene to determine the regression model that gave the largest R² value at the P<0.01 level of probability. The multiple regression model included five significant unlinked markers and one significant interaction. The model gave an R² value of which accounted for 48.8% of the variation for resistance to P. tritici-repentis isolate Pti2 in adult wheat plants of this population. The major QTL identified in adults was associated with the locus identified by the RFLP marker XGli1 located on chromosome 1AS and accounted for 26.1% of the variation for resistance. This is the same marker found to be associated with the QTL QTsc.ndsu-1A in seedlings of this population.