Fine mapping, phenotypic characterization and validation of non-race-specific resistance to powdery mildew in a wheat–Triticum militinae introgression line.

Jakobson, I., Reis, D., Tiidema, A., Peusha, H., Timofejeva, L., Valárik, M., Kladivová, M., Šimková, H., Doležel, J., Järve, K.

Abstract: Introgression of several genomic loci from tetraploid Triticum militinae into bread wheat cv. Ta¨hti has increased resistance of introgression line 8.1 to powdery mildew in seedlings and adult plants. In our previous work, only a major quantitative trait locus (QTL) on chromosome 4AL of the line 8.1 contributed significantly to resistance, whereas QTL on chromosomes 1A, 1B, 2A, 5A and 5B were detected merely on a suggestive level. To verify and characterize all QTLs in the line 8.1, a mapping population of double haploid lines was established. Testing for seedling resistance to 16 different races/mixtures of Blumeria graminis f. sp. tritici revealed four highly significant nonrace- specific resistance QTL including the main QTL on chromosome 4AL, and a race-specific QTL on chromosome 5B. The major QTL on chromosome 4AL (QPm.tut- 4A) as well as QTL on chromosome 5AL and a newly detected QTL on 7AL were highly effective at the adult stage. The QPm.tut-4A QTL accounts on average for 33–49 % of the variation in resistance in the double haploid population. Interactions between the main QTL QPm.tut-4A and the minor QTL were evaluated and discussed. A population of 98 F2 plants from a cross of susceptible cv. Chinese Spring and the line 8.1 was created that allowed mapping the QPm.tut-4A locus to the proximal 2.5-cM region of the introgressed segment on chromosome 4AL. The results obtained in this work make it feasible to use QPm.tut-4A in resistance breeding and provide a solid basis for positional cloning of the major QTL.
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IEB authors: Jaroslav Doležel, Hana Šimková, Miroslav Valárik