Insights into the resistance of a synthetically-derived wheat to Septoria tritici blotch disease: less is more

Abstract

Background Little is known about the initial, symptomless (latent) phase of the devastating wheat disease Septoria tritici blotch. However, speculations as to its impact on fungal success and disease severity in the field have suggested that a long latent phase is beneficial to the host and can reduce inoculum build up in the field over a growing season. The winter wheat cultivar Stigg is derived from a synthetic hexaploid wheat and contains introgressions from wild tetraploid wheat Triticum turgidum subsp. dicoccoides , which contribute to cv. Stigg’s exceptional STB resistance, hallmarked by a long latent phase. We compared the early transcriptomic response to Zymoseptoria tritici of cv. Stigg to a susceptible wheat cultivar, to elucidate the mechanisms of and differences in pathogen recognition and disease response in these two hosts. Results The STB-susceptible cultivar Longbow responds to Z. tritici infection with a stress response, including activation of hormone-responsive transcription factors, post translational modifications, and response to oxidative stress. The activation of key genes associated with these pathways in cv. Longbow was independently observed in a second susceptible wheat cultivar based on an independent gene expression study. By comparison, cv. Stigg is apathetic in response to STB, and appears to fail to activate a range of defence pathways that cv. Longbow employs. Stigg also displays some evidence of sub-genome bias in its response to Z. tritici infection, whereas the susceptible cv. Longbow shows even distribution of Z. tritici responsive genes across the three wheat sub-genomes. Conclusions We identify a suite of disease response genes that are involved in early pathogen response in susceptible wheat cultivars that may ultimately lead to susceptibility. In comparison, we hypothesise that rather than an active defence response to stave off disease progression, cv. Stigg’s defence strategy is molecular lethargy, or a lower-amplitude of pathogen recognition that may stem from cv. Stigg’s wild wheat-derived ancestry. Overall, we present insights into cv. Stigg’s exceptional resistance to STB, and present key biological processes for further characterisation in this pathosystem.

Mixed infections of Zymoseptoria tritici lead to reduced Septoria tritici blotch disease symptoms

“…D09 and D10 have the isoform I03 while isolate D01 has a unique isoform, similar to I03, but it does not have a tyrosine to phenylalanine change at residue 50 (Stephens et al, 2021). Nevertheless, we found no relationship between the aggressiveness of isolates and are moderately resistant (Benbow et al, 2020;Brennan et al, 2020;Chartrain et al, 2005).…”

“…Longbow. This may reflect that Longbow ( Stb15 ) is a susceptible cultivar (Arraiano et al, 2007) and may be unable to trigger defence responses, whereas Stigg and Flame ( Stb6 ) are moderately resistant (Benbow et al, 2020; Brennan et al, 2020; Chartrain et al, 2005).…”

Novel genomic regions on chromosome 5B controlling wheat powdery mildew seedling resistance under Egyptian conditions

“…Network 3, controlled by TraesCS5B02G006600 gene model, was found to contain four different pathways that control the activity of serine hydrolase in wheat. The regulation of serine/threonine was involved in wheat resistance to Septoria blotch disease ( Benbow et al., 2020 ; Zhou et al., 2020 ). Furthermore, Serine/threonine kinase gene was reported as a key member of Pm21 powdery mildew resistance gene ( Cao et al., 2011 ).…”

Evaluation of the susceptibility of modern, wild, ancestral, and mutational wheat lines to Septoria tritici blotch disease

“…Stigg, the cv. LW‐96–2930 is the probable contributor of its STB resistance (Benbow et al, 2020). We observed isolate‐specific responses to the different Z .…”

“…The STB resistant hexaploid elite wheat cv. Stigg (Benbow et al, 2020; Hehir et al, 2018; Odilbekov et al, 2019; Welch et al, 2017) and susceptible cv. Longbow (Chartrain et al, 2004; Chartrain, Joaquim, et al, 2005), and wild‐type Cadenza seeds were used as STB checks in the STB experiments.…”