MlUM15: an Aegilops neglecta‐derived Powdery Mildew Resistance Gene in Common Wheat

Abstract

Powdery mildew, caused by Blumeria graminis f. sp. tritici, is a major fungal disease of wheat (Triticum aestivum L.). Host plant resistance is a reliable, economical, and environmentally benign form of disease prevention. The identification of molecular markers linked with resistance genes can facilitate marker‐assisted selection and enable breeders to pyramid several major genes for powdery mildew resistance in a single cultivar. The wheat germplasm line NC09BGTUM15 (NC‐UM15) possesses the first powdery mildew resistance gene introgressed from Aegilops neglecta Req. ex Bertol. Greenhouse and field evaluations of F2:3 families derived from a cross between NC‐UM15 and the susceptible cultivar ‘Saluda’ indicated that a single dominant gene, temporarily designated MlUM15, conferred resistance to powdery mildew. Bulked segregant analysis (BSA) showed that several simple sequence repeat (SSR), sequence tag site (STS), and single nucleotide polymorphism (SNP) markers specific to chromosome 7AL segregated with the resistance gene. The most likely marker order was Xwmc525/IWA8057‐0.7 cM‐Xcfa2257‐0.4 cM‐ MlUM15 −0.8 cM‐Xcfa2240‐2.8 cM‐Xmag2185‐3.4cM‐IWA2929‐5.4 cM‐ IWA4434. The multiallelic Pm1 locus and several temporarily‐designated genes map to this region of chromosome 7AL. Detached‐leaf tests revealed that NC‐UM15 had a different disease response pattern from genotypes carrying Pm37, five temporarily‐designed genes in the region, and all alleles of the Pm1 complex except Pm1b. The MlUM15‐resistance gene is most likely a novel source of powdery mildew resistance. However, allelism tests with Pm1 and further detached‐leaf tests will be required to elucidate the relationship between MlUM15 and other Pm loci in the distal region of 7AL.

Molecular and Cytogenetic Characterization of Six Wheat-Aegilops markgrafii Disomic Addition Lines and Their Resistance to Rusts and Powdery Mildew

“…Powdery mildew tests were conducted at the USDA-ARS, Plant Science Research Unit, Raleigh, NC, using the detached-leaf method as described by Worthington et al (2014) . Twenty isolates representing differing United States regional virulence profiles were used for tests.…”

“…To simplify presentation, two Montana isolates are included as “Great Plains” isolates despite originating west of the Great Plains because they exhibit a similar virulence profile to isolates from the Great Plains ( Cowger et al, 2018 ). Inoculations were performed following Worthington et al (2014) . In brief, two 1.5-cm detached leaf segments from each genotype were floated on 0.5% water agar containing 50 mg L -1 benzimidazole in a Petri plate.…”

Virulence Differences in Blumeria graminis f. sp. tritici from the Central and Eastern United States

“…Although partially mildew-resistant wheat backgrounds are essential and have provided durable resistance in some settings (Brown 2015), genes that even temporarily confer high levels of resistance have also been necessary to achieve adequate protection of wheat crops in the mid-Atlantic United States. In North Carolina, starting in 1987, 16 new and highly effective resistance sources have been identified in diploid and tetraploid common wheat relatives and introgressed into a soft red winter wheat background adapted to the eastern United States, resulting in five Pm gene and two temporary gene designations (Cowger et al 2012;Petersen et al 2015;Worthington et al 2014). These genes were introgressed from relatives in the Triticum and Aegilops genera.…”

Characterization of the Resistance to Powdery Mildew and Leaf Rust Carried by the Bread Wheat Cultivar Victo

“…Q Pm. gb-7A was included completely in the physical regions, from 12.37 Mbp to 15.22 Mbp, identified by Pm U (from 717.0 to 732.3 Mbp), ml W18 (from 724.1 to 736.5 Mbp), and ml UM15 (from 717.0 to 732.3 Mbp) [ 45 , 46 , 47 ].…”