A global perspective on the genetic architecture of susceptibility to spot form net blotch in barley

Authors: MALVESTITI, MICHELE - North Dakota State University; Skiba, Ryan; ALAOFIN, SEFUNMI - North Dakota State University; Yang, Shengming; Fiedler, Jason; LIU, ZHAOHUI - North Dakota State University; Friesen, Timothy

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2026
Publication Date: 4/28/2026
Citation: Malvestiti, M., Skiba, R.M., Alaofin, S., Yang, S., Fiedler, J.D., Liu, Z., Friesen, T.L. 2026. A global perspective on the genetic architecture of susceptibility to spot form net blotch in barley. Theoretical and Applied Genetics. 139.Article 139. https://doi.org/10.1007/s00122-026-05250-5.
DOI: https://doi.org/10.1007/s00122-026-05250-5

Interpretive Summary: Spot form net blotch (SFNB), caused by Pyrenophora teres f. maculata, is a major disease of barley worldwide. The pathogen uses effector proteins to exploit host susceptibility genes, making resistance breeding difficult and increasing reliance on fungicides. Researchers analyzed three barley populations using global pathogen isolates and identified four susceptibility loci on chromosomes 2H, 4H, and 7H. The Chr7H locus was consistently linked to severe disease and is the most critical target for breeding. These findings enable marker-assisted selection to eliminate susceptibility alleles, particularly Chr7H, accelerating development of resistant cultivars and reducing reliance on fungicides. This work advances understanding of necrotrophic pathogen-host interactions and provides actionable tools for improving barley resilience globally.

Technical Abstract: The necrotrophic fungal pathogen Pyrenophora teres f. maculata causes spot form net blotch, a worldwide-reported disease of barley. The fungus uses effector proteins to promote infection, which may act in an inverse gene-for-gene manner, thereby targeting dominant host susceptibility genes. Previous research highlighted the complexity of the genetics in the barley-P. teres f. maculata interaction. In this study, we evaluated three new barley populations that segregate for susceptibility to spot form net blotch (Hockett × PI 67381, TR 326 × PI 67381 and PI 392501 × PI 67381). By crossing three different susceptible barley lines with the same resistant line, we sought to determine whether the susceptible lines contained common susceptibility genes. The populations were genotyped, mapped, and inoculated with a global collection of P. teres f. maculata isolates. Disease phenotyping and QTL analysis were conducted to identify host loci associated with susceptibility and to understand whether geographically diverse isolates harbor common effectors. Four independent loci showed a significant association with susceptibility and mapped to barley chromosome (Chr)2H, Chr4H, and Chr7H, respectively, whereby the Chr7H locus provided the strongest contribution to disease. In all three populations, the same genomic position on Chr7H was associated with susceptibility and targeted by seven of ten fungal isolates, whereas the QTL identified on Chr2H mapped to the same position in two populations. This indicates that the same susceptibility gene segregating on Chr7H is present in all three barley lines, whereas the same gene segregating at Chr2H is present in both barley lines Hockett and TR 326.