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

Abstract

Introgression of several genomic loci from tetraploid Triticum militinae into bread wheat cv. Tähti 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 non-race-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 F(2) 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.

Genetic basis of qualitative and quantitative resistance to powdery mildew in wheat: from consensus regions to candidate genes

“…For example, MQTL2 combined the two QTL mapped in a population that derives from a cross between T. militinae (Zhuk.) and a wheat cultivar [57,58], and one QTL where the resistance resulted from a variety that had T. timopheevii in its genetic background. As T. militinae derives from T. timopheevii , the resistance source might be the same.…”

“…Chromosome 1A was characterized by the presence of introgression from T. militinae , which started from the marker Xpsp2999 (47.2 cM), as proposed by Jakobson et al [58], where MQTL1 and MQTL2 were located, also including Pm3g , Pm3a , Mlar , and Pm3e , where their resistance derives instead from T. aestivum . A gene-rich region was identified on chromosome 2A, corresponding to MQTL4.…”

Molecular characterization of a new powdery mildew resistance gene Pm54 in soft red winter wheat

“…Similarly, several QTL have been reported on chromosome 4A, and most of them are of minor effect and only detected in certain environments, except QPm.tut-4A, the race non-specific resistance QTL from a T. militinae translocation (Jakobson et al 2006(Jakobson et al , 2012. QPm.tut-4A and a minor QTL identified in US hard winter wheat cultivar '2174' are both closely linked to the marker Xgwm160 and assigned to the most distal part of 4AL (Chen et al 2009;Jakobson et al 2012).…”

Preparation of sub-genomic fractions enriched for particular chromosomes in polyploid wheat

“…Tähti and cv. Chinese Spring (Jakobson et al 2012). The owm31 marker amplified a 220 bp fragment from chromosomes 4A and 4B and also a 200 bp fragment from chromosomes 7D and 7B.…”

“…The cv. Tähti was chosen because its chromosome 4A bears a QPm-tut-4A gene providing resistance to powdery mildew (Jakobson et al 2012), and we have been involved in a project on cloning this gene. The ability to prepare chromosome 4A enriched fractions as described in the present work greatly aided the project.…”