Remarkable recent changes in genetic diversity of the avirulence gene AvrStb6 in global populations of the wheat pathogen Zymoseptoria tritici

A - Papers appearing in refereed journals

Stephens, C., Olmez, F., Blyth, H., McDonald, M., Bansal, A., Turgay, E. B., Hahn, F., Saintenac, C., Nekrasov, V., Solomon, P., Milgate, A., Fraaije, B. A., Rudd, J. J. and Kanyuka, K. 2021. Remarkable recent changes in genetic diversity of the avirulence gene AvrStb6 in global populations of the wheat pathogen Zymoseptoria tritici. Molecular Plant Pathology. 22 (9), pp. 1121-1133. https://doi.org/10.1111/mpp.13101

AuthorsStephens, C., Olmez, F., Blyth, H., McDonald, M., Bansal, A., Turgay, E. B., Hahn, F., Saintenac, C., Nekrasov, V., Solomon, P., Milgate, A., Fraaije, B. A., Rudd, J. J. and Kanyuka, K.
Abstract

Septoria tritici blotch (STB), caused by the fungus Zymoseptoria tritici, is one of the most economically important diseases of wheat. Recently, both factors of a gene-for-gene interaction between Z. tritici and wheat, the wheat receptor-like kinase Stb6 and the Z. tritici secreted effector protein AvrStb6, have been identified. Previous analyses revealed a high diversity of AvrStb6 haplotypes present in historic Z. tritici isolate collections, with up to ~ 18% of analysed isolates possessing the avirulence isoform of AvrStb6 identical to that originally identified in the reference isolate IPO323. With Stb6 present in many commercial wheat cultivars globally, we aimed to assess potential changes in AvrStb6 genetic diversity and the incidence of haplotypes allowing evasion of Stb6-mediated resistance in more recent Z. tritici populations. Here we show, using targeted re-sequencing of AvrStb6, that this gene is universally present in field isolates sampled from major wheat-growing regions of the world between 2013–2017. However, in contrast to the data from studies of historic isolates, our study revealed a complete absence of the originally described avirulence isoform of AvrStb6 amongst modern Z. tritici isolates. Moreover, a remarkably small number of haplotypes, each encoding AvrStb6 protein isoforms conditioning virulence on Stb6-containing wheat, were found to predominate among modern Z. tritici isolates. A single virulence isoform of AvrStb6 was found to be particularly abundant throughout the global population. These findings indicate that, despite the ability of Z. tritici to sexually reproduce on resistant hosts, AvrStb6 avirulence haplotypes tend to be eliminated in subsequent populations.

KeywordsSeptoria tritici blotch; Triticum aestivum; Disease resistance; Stb6; Population biology; Fungal effector; CRISPR/Cas9
Year of Publication2021
JournalMolecular Plant Pathology
Journal citation22 (9), pp. 1121-1133
Digital Object Identifier (DOI)https://doi.org/10.1111/mpp.13101
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeDFW - Designing Future Wheat - Work package 2 (WP2) - Added value and resilience
Nottingham-Rothamsted Doctoral Training Partnership
Publisher's version
Accepted author manuscript
Supplemental file
Output statusPublished
Publication dates
Online14 Jul 2021
Publication process dates
Accepted03 Jun 2021
PublisherWiley
ISSN1464-6722

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