Abdullah F. Alhashel, Jason D. Fiedler, Raja Sekhar Nandety, Ryan M. Skiba, Robert S. Bruggeman, Thomas Baldwin, Timothy L. Friesen & Shengming Yang

Theoretical and Applied Genetics volume 136, Article number: 118

Key message

Genetic characterization of a major spot form net blotch susceptibility locus to using linkage mapping to identify a candidate gene and user-friendly markers in barley.

Abstract

Spot form net blotch (SFNB), caused by the necrotrophic fungal pathogen Pyrenophora teres f. maculata (Ptm), is an economically important foliar diseases in barley. Although various resistance loci have been identified, breeding for SFNB-resistant varieties has been hampered due to the complex virulence profile of Ptm populations. One resistance locus in the host may be effective against one specific isolate, but it may confer susceptibility to other isolates. A major susceptibility QTL on chromosome 7H, named Sptm1, was consistently identified in many studies. In the present study, we conduct fine mapping to localize Sptm1 with high resolution. A segregating population was developed from selected F₂ progenies of the cross Tradition (S) × PI 67381 (R), in which the disease phenotype was determined by the Sptm1 locus alone. Disease phenotypes of critical recombinants were confirmed in the following two consecutive generations. Genetic mapping anchored the Sptm1 gene to an ⁓400 kb region on chromosome 7H. Gene prediction and annotation identified six protein-coding genes in the delimited Sptm1 region, and the gene encoding a putative cold-responsive protein kinase was selected as a strong candidate. Therefore, providing fine localization and candidate of Sptm1 for functional validation, our study will facilitate the understanding of susceptibility mechanism underlying the barley-Ptm interaction and offers a potential target for gene editing to develop valuable materials with broad-spectrum resistance to SFNB.

See https://link.springer.com/article/10.1007/s00122-023-04367-1

Fig. 2: Fine mapping of Sptm1. Genetic mapping was conducted sequentially with 178 (A) and 524 (B) F_2:3 individuals representing 356 and 1048 gametes, respectively. Phenotypes of critical recombinants were first confirmed with F_3:4 plants from which ICRs were selected. At least 30 ICRs for each recombinant were also tested to verify the disease response. The ICRs used to delimit the Sptm1 gene are shown by a combination of differential boxes. Black box represents homozygous susceptible genotype, and empty for homozygous resistant. Numbers below the linkage group indicate the number of recombination breakpoints separating the marker from Sptm1. A total of six protein-coding genes were identified in the Sptm1 region spanning ~ 400 kb (C). The maps are drawn to scale. M, marker; ICR, immortal critical recombinant; R, resistant; S, susceptible; G, gene.