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. 2020 Jul 3;20(1):314.
doi: 10.1186/s12870-020-02525-x.

Genetic analysis of loose smut (Ustilago tritici) resistance in Sonop spring wheat

Dinushika Thambugala  1 , Jim G Menzies  1 , Ron E Knox  2 , Heather L Campbell  2 , Curt A McCartney  3
Affiliations

Genetic analysis of loose smut (Ustilago tritici) resistance in Sonop spring wheat

Dinushika Thambugala et al. BMC Plant Biol. .

Abstract

Background: The genetics of resistance to loose smut of wheat (Triticum aestivum L.) caused by the fungus Ustilago tritici (Pers.) Rostr. is not well understood. This study examines loose smut resistance in Sonop (TD-14), a South African spring wheat variety. A doubled haploid (DH) population of 163 lines derived from the cross Diamont/TD-14 was studied. The parents and progenies were inoculated with U. tritici races T2, T9, and T39 individually in growth facilities at Morden and Swift Current, Canada. Loose smut incidence (LSI) and partial loose smut resistance (PLSR) were assessed.

Results: A whole genome linkage map was developed consisting of 11,519 SNP loci found on 31 linkage groups spanning 2845 cM. A new major resistance gene Ut11 was located to the distal end of chromosome arm 7BS. Ut11 conferred resistance to U. tritici race T2, but not races T9 and T39. Quantitative trait locus (QTL) mapping identified four QTL controlling LSI in the Diamont/TD-14 DH population on chromosomes 3B, 4B, 5B, and 7B (at Ut11) with TD-14 contributing the resistance alleles at three of these loci. The major QTL QUt.mrc-5B was effective against all three races and explained up to 81% of the phenotypic variation. The only QTL identified for PLSR coincided with the LSI QTL QUt.mrc-5B indicating that this locus affected both loose smut incidence and partial smutting of spikes.

Conclusions: A race-specific resistance gene Ut11 and a broadly effective resistance QTL QUt.mrc-5B were the main loci controlling loose smut resistance in the differential line TD-14 (cultivar Sonop). This study provides insight into the genetics of loose smut resistance in spring wheat Sonop and the single nucleotide polymorphism (SNP) markers linked to the resistance gene Ut11 and QTL QUt.mrc-5B will be useful for selecting loose smut resistance in breeding programs.

Keywords: Disease resistance; Linkage analysis; Loose smut; Quantitative trait locus (QTL); Sonop (TD-14); Triticum aestivum; Ustilago tritici.

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Conflict of interest statement

CAM is an Associate Editor of BMC Plant Biology (Genetics and crop biotechnology). The authors declare that they have no other competing interests.

Figures

Fig. 1
Fig. 1
Loose smut symptoms caused by Ustilago tritici on common spring wheat: a resistant, b partially resistant, and c susceptible (fully smutted)
Fig. 2
Fig. 2
Frequency distribution of a loose smut incidence (LSI %) and b fully smutted index (FSI %) within the Diamont/TD-14 DH mapping population in response to Ustilago tritici individual races T2, T9 and T39 based upon the pooled dataset. Values for parents Diamont and TD-14 are indicated
Fig. 3
Fig. 3
QTL QUt.mrc-5B region on chromosome 5B (linkage group 5B.1) associated with resistance to U. tritici races T9 and T39. Displayed LOD scans are based upon interval mapping. Map distances are in centiMorgans (cM). The LOD threshold value for declaring QTL was 3.2. Mor = Morden, Swift = Swift Current
Fig. 4
Fig. 4
Location of the loose smut resistance gene Ut11 on the distal end of chromosome arm 7BS. The QTL LOD scan is presented on the right showing specificity for U. tritici race T2. The LOD threshold value for declaring QTL was 3.2. Map distances are shown in centiMorgans (cM). Mor = Morden, Swift = Swift Current
See this image and copyright information in PMC

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