Identification and assessment of two major QTLs for dwarf bunt resistance in winter wheat line ‘IDO835’

Abstract

Key message Two major dwarf bunt resistance QTLs were mapped to a known Bt9 locus and a novel locus. The associated KASP markers were developed and validated in other two populations. Abstract Dwarf bunt (DB), caused by Tilletia controversa J.G. Kühn, and common bunt (CB), caused by T. caries and T. foetida, are two destructive diseases that reduce grain yield and quality in wheat. Breeding for bunt-resistant cultivars is important in many wheat production areas, especially where organic wheat is grown. However, few molecular markers have been used in selection of bunt resistance. In the present study, a doubled haploid (DH) population derived from the buntresistant line 'IDO835' and the susceptible cultivar 'Moreland' was evaluated for DB resistance in a field nursery in Logan, Utah, for four growing seasons. The population was genotyped with the Illumina 90 K SNP iSelect marker platform. Two major QTLs were consistently identified on chromosomes 6DL (Q.DB.ui-6DL) and 7AL (Q.DB.ui-7AL), explaining up to 53% and 38% of the phenotypic variation, respectively. Comparative study suggested that Q.DB.ui-6DL was located in the same region as the CB resistance gene Bt9, and Q.DB.ui-7AL was located at a novel locus for bunt resistance. Based on Chinese Spring reference sequence and annotations (IWGSC RefSeq v1.1), both resistance QTLs were mapped to disease resistance gene-rich (NBS-LRR and kinase genes) regions. To validate the identified QTL and design user-friendly markers for MAS, five SNPs were converted to Kompetitive Allele-Specific PCR (KASP) markers and used to genotype two validation panels, including a DH population and a diverse winter wheat population from USDA-ARS National Small Grain Collection, as well as a Bt gene investigation panel, consisting of 15 bunt differential lines and 11 resistant lines.Communicated by Beat Keller.Blair Goates: Retired.

Genetic characterization and genome-wide association mapping for dwarf bunt resistance in bread wheat accessions from the USDA National Small Grains Collection

“…Two major QTL, Q.DB.ui-7DS (Chen et al 2016), Q.DB-6DL (Steffan et al 2017;Wang et al 2019) and Q.DB.ui-7AL (Wang et al 2019) that were previously reported in biparental populations, were not detected in this study. The QTL Q.DB.ui-7DS was reported in the 'Rio Blanco'/'IDO444' population on 7DS with a peak marker, wPt-2565, at 5.9 Mbp near the telomere (Chen et al 2016).…”

“…However, our GWAS did not detect any markers significantly associated with 6DL in any of the data sets. Using a biparental mapping population derived from a University of Idaho wheat breeding line 'IDO835', Wang et al (2019) found two QTL for DB resistance, one on 6DL corresponding with the Bt9 locus, and one on 7AL. We used the resistant haplotypes for both loci to find accessions that contain these QTL (Table 6, Supplementary File 9).…”

“…Highly resistant landrace accessions with dwarf bunt (DB) normalized incidence ≤ 1% across all data sets, bunt differentials and several known resistant and susceptible accessions with corre-sponding best linear unbiased estimates (BLUE) values and the presence (+) or absence (−) of the resistant allele haplotypes from each marker-trait association group detected in this study a The 6DL haplotype SNP markers are reported inWang et al (2019) b 7AL haplotype SNP markers are reported inWang et al (2019) c 7DS haplotype SSR markers are reported inChen et al (2016), and SNP markers were reported by RuiWang (personal communication) , but none of the highly resistant accessions contained the 6DL or 7AL haplotype(Table 6, Supplementary File 9).…”

Genetic mapping of the common and dwarf bunt resistance gene Bt12 descending from the wheat landrace PI119333

“…Bt10 was mapped to the short arm of chromosome 6D (Menzies et al 2006) and Bt9 was mapped by Steffan et al (2017) to the long arm of chromosome 6D. Both genes were validated in independent populations (Singh et al 2016;Wang et al 2019), and DNA markers linked to the genes have been published for the purpose of marker-assisted selection (MAS) of Bt9 (Steffan et al 2017;Wang et al 2019) and Bt10 (Laroche et al 2000;Menzies et al 2006). Bunt resistance is mediated partly by non-race specific quantitative trait loci (QTL), and 24 QTL for bunt resistance have been identified to date by QTL mapping in wheat.…”

“…A major QTL for DB resistance was identified by Chen et al (2016) on the short arm of chromosome 7D. Minor DB QTL were identified on 1A (Chen et al 2016), 2B (Chen et al 2016), and 7A (Wang et al 2019). Association mapping studies identified several significant marker traits association for CB.…”