Host and pathogen genetics reveal an inverse gene-for-gene association in the Pyrenophora teres f. maculata – barley pathosystem

Authors: SKIBA, RYAN - Oak Ridge Institute For Science And Education (ORISE); Wyatt, Nathan; KARIYAWASAM, GAYAN - North Dakota State University; Fiedler, Jason; Yang, Shengming; BRUEGGEMAN, ROBERT - Washington State University; Friesen, Timothy

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2022
Publication Date: 9/5/2022
Citation: Skiba, R., Wyatt, N.A., Kariyawasam, G., Fiedler, J.D., Yang, S., Brueggeman, R., Friesen, T.L. 2022. Host and pathogen genetics reveal an inverse gene-for-gene association in the Pyrenophora teres f. maculata – barley pathosystem. Theoretical and Applied Genetics. https://doi.org/10.1007/s00122-022-04204-x.
DOI: https://doi.org/10.1007/s00122-022-04204-x

Interpretive Summary: Spot-form net blotch (SFNB), caused by the fungus (Pyrenophora teres f. maculata), is an emerging and economically important foliar disease of barley worldwide. We used both barley and fungus genetics to characterize how this host and pathogen interact. We showed for the first time, an inverse gene for gene relationship in spot form net blotch of barley, where virulence factors produced by the pathogen are targeting vulnerable barley susceptibility genes, resulting in disease. The characterization of the spot form net blotch of barley interaction is important for other scientists working on this and other necrotrophic pathosystems, as well as for barley breeders working to breed for durable resistance to this economically important disease.

Technical Abstract: Although models have been proposed to broadly explain how plants and pathogens interact and coevolve, each interaction evolves independently, resulting in various scenarios of host manipulation and plant defense. Spot form net blotch (SFNB) is a foliar disease of barley caused by Pyrenophora teres f. maculata. We developed a barley population (Hockett x PI 67381) segregating for resistance to a diverse set of P. teres f. maculata isolates. Quantitative trait locus (QTL) analysis identified major loci on barley chromosomes (Chr) 2H and 7H associated with resistance/susceptibility. Subsequently, we used avirulent and virulent P. teres f. maculata isolates to develop a pathogen population, identifying two major virulence loci located on Chr1 and Chr2. To further characterize this host-pathogen interaction, progeny from the pathogen population harboring virulence alleles at either the Chr1 or Chr2 locus were phenotyped on the Hockett x PI 67381 population. Progeny harboring only the Chr1 virulence allele lost the barley Chr7H association but maintained the 2H association. Conversely, isolates harboring only the Chr2 virulence allele lost the barley Chr2H association but maintained the 7H association. Hockett × PI 67381 F2 individuals showed susceptible:resistant ratios not significantly different than 15:1 and results from F2 inoculations using the single virulence genotypes were not significantly different from a 3:1 (S:R) ratio, indicating two dominant susceptibility genes. Collectively, this work shows that P. teres f. maculata virulence alleles at the Chr1 and Chr2 loci are targeting the barley 2H and 7H susceptibility alleles in an inverse gene-for-gene manner to facilitate colonization.