Molecular mapping of loci conferring susceptibility to spot blotch and resistance to powdery mildew in barley using the sequencing-based genotyping approach

Authors: LENG, YUEQIANQ - North Dakota State University; ZHAO, MINGXIA - North Dakota State University; Fiedler, Jason; DREISEITL, ANTONIN - Agrotest Fryo Ltd; Chao, Shiaoman; LI, XUEHUI - North Dakota State University; ZHONG, SHAOBIN - North Dakota State University

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2019
Publication Date: 1/5/2020
Citation: Leng, Y., Zhao, M., Fiedler, J.D., Dreiseitl, A., Chao, S., Li, X., Zhong, S. 2020. Molecular mapping of loci conferring susceptibility to spot blotch and resistance to powdery mildew in barley using the sequencing-based genotyping approach. Phytopathology. 110(2):440-446. https://doi.org/10.1094/PHYTO-08-19-0292-R.
DOI: https://doi.org/10.1094/PHYTO-08-19-0292-R

Interpretive Summary: Spot blotch and powdery mildew are two major fungal diseases of barley that attack the leaves of the plant and decrease yield and quality of the grain. Genetic sources of resistance are the best tool breeders can use to develop lines that overcome the disease-causing pathogens. To successfully utilize these genetic sources, we need to locate the specific regions of the genome that influence disease. In this study we used a synthetic mapping cross to identify two specific genomic loci from a barley line resistant to both diseases. These results provide novel information about the disease mechanism of spot blotch and validate previous studies in powdery mildew research. This study is important for barley breeders as these genetic resistance loci and associated molecular markers can be immediately used to develop new resistant cultivars.

Technical Abstract: Spot blotch caused by Bipolaris sorokiniana and powdery mildew caused by Blumeria graminis f. sp. hordei are two important diseases of barley. To map genetic loci controlling susceptibility and resistance to these diseases in the barley cultivar Bowman and barley line ND5883, a mapping population consisting of 138 recombinant inbred lines (RILs) was developed from the cross between Bowman and ND5883. Genotyping of Bowman and ND5883 as well as the RILs by genome sequencing revealed 7,393,920 SNPs between the two parents, and 5,215 SNP markers segregated in the population. A genetic map was constructed with 852 unique SNP markers, which formed 9 linkage groups covering 1014.81 cM in length with an average marker density of 1.19 cM. Bowman and ND5883 showed distinct infection responses (IRs) at the seedling stage to two isolates (ND90Pr and ND85F) belonging to different pathotypes of B. sorokiniana and one isolate (Race I) of B. graminis f. sp. hordei. Genetic analysis of the RILs showed one major gene controls the susceptibility to B. sorokiniana isolate ND90Pr and another major gene confers resistance to B. graminis f. sp. hordei isolate, respectively. The gene (Scs6) conferring susceptibility to spot blotch caused by ND90Pr was mapped on chromosome 1H of Bowman as previously reported. The gene (Mla 8) conferring resistance to powdery mildew in ND5883 was tightly linked to the Rcs6/Scs6 locus on chromosome 1H. QTL analysis identified two QTL (QSbs-1H-P1 and QSbs-7H-P1) responsible for susceptibility to spot blotch caused by B. sorokiniana isolate ND85F in ND5883, which are located on chromosome 1H and 7H, respectively. QSbs-7H-P1 was mapped to the same region as Rcs5, while QSbs-1H-P1 may represent a novel allele conferring seedling stage susceptibility to isolate ND85F. Identification and molecular mapping of the loci for spot susceptibility and powdery mildew resistance will facilitate development of barley cultivars with resistance to spot blotch and powdery mildew.