Elucidating mechanisms of non-host resistance towards Septoria passerinii and Zymoseptoria tritici in wheat and barley

Authors: Million, Cassidy; Crane, Charles; Goodwin, Stephen - Steve

Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/10/2019
Publication Date: 1/11/2020
Citation: Million, C.R., Crane, C.F., Goodwin, S.B. 2020. Elucidating mechanisms of non-host resistance towards Septoria passerinii and Zymoseptoria tritici in wheat and barley. Plant and Animal Genome Conference Proceedings. Jan 11-15, 2020, San Diego, CA.

Interpretive Summary:

Technical Abstract: Non-host resistance, by definition, is complete, durable resistance of a plant species to a potential pathogen. Septoria passerinii is a pathogen of barley but not wheat, while Zymoseptoria tritici (previously Mycosphaerella graminicola) infects wheat but not barley. Wheat displays gene-for-gene resistance responses to Z. tritici with ~21 genes mapped to date. Little is known about the mechanisms of resistance and specifically whether different resistance genes in the same host utilize common or variable mechanisms to achieve the defense response. Thus, the objective of this study is to identify the mechanisms of resistance in the host and non-host responses towards two pathogens, S. passerinii and Z. tritici, and to test whether similar mechanisms are being utilized by the host and non-host responses. To test this, RNA sequencing was carried out at 5 time points ranging from fungal penetration to the late infection stage (1, 3, 6, 10, and 17 days after inoculation). The non-host interaction consisted of S. passerinii inoculated onto a wheat genotype that is susceptible to Z. tritici (Taichung 29), while Z. tritici (isolate IPO323) was inoculated onto a normally susceptible barley genotype. Host interactions consisted of Z. tritici inoculated onto two wheat lines containing resistance genes Stb2 (on wheat chromosome 1BS) and Stb3 (7AS) plus the Taichung 29 susceptible genotype, and S. passerinii inoculated onto resistant and susceptible barley genotypes. Our findings suggest that non-host resistance responses have different timings and gene expression patterns compared to host (R gene) responses. In both interactions at 1 dai, a large number of differentially expressed genes (DEGs) were measured. In the non-host response, a similar number of DEGs are measured throughout the entire infection period, whereas in the host response DEGs decreased over the infection period. The non-host response of barley to Z. tritici is induced, not constitutive. This study gives a greater insight into the mechanisms of non-host resistance as well as compatible and incompatible interactions in the host response.