Abstract
Wheat blast caused by the Triticum pathotype of Pyricularia oryzae is a serious threat to wheat production in South America and Asia. Rmg8 is a promising gene for resistance to the wheat blast fungus found in common wheat. To predict its durability, stability of its corresponding avirulence gene, AVR-Rmg8, was evaluated based on the genome structure around AVR-Rmg8 in an isolate from Triticum and on polymorphisms of AVR-Rmg8 in isolates from Lolium spp., which are closely related to Triticum isolates. AVR-Rmg8 was located in a gene-rich, repeat-poor region, suggesting that AVR-Rmg8 is not as easily lost as avirulence genes located in repeat-rich regions. This finding implies that Rmg8 is relatively durable compared with resistance genes corresponding to avirulence genes in repeat-rich regions. AVR-Rmg8 was widely distributed in Lolium isolates and comprised three types or variants, eL1, eL2, and eL3. Complementation tests revealed that eL1 and eL2 were functional and recognized by Rmg8. In eL3, however, retrotransposon Pyret was inserted into the ORF of AVR-Rmg8. Actually, three isolates carrying eL3 were virulent on common wheat cultivar S-615 carrying Rmg8, indicating that the insertion of Pyret caused a loss of function of AVR-Rmg8. Nevertheless, the three isolates have survived in nature, suggesting that AVR-Rmg8 is not indispensable for survival of Pyricularia isolates and, in turn, that Rmg8 is not likely to be completely durable.
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Acknowledgements
We thank Dr. M. Kusaba, Saga University, for providing the isolates from Lolium multiflorum and critically reading the manuscript. We also thank Dr. K. Tsunewaki, Emeritus Professor of Kyoto University, Dr. H. Tsujimoto, Tottori University, and Dr. K. Kato, Okayama University, for providing seeds of the wheat lines, and Dr. B. Valent, Kansas State University, for various comments on the manuscript. This research was supported by the grant "International Collaborative Research Project for Solving Global Issues" from the Agriculture, Forestry and Fisheries Research Council Secretariat, Ministry of Agriculture, Forestry and Fisheries (MAFF), Japan.
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The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession numbers, LC535796 (eL1), LC535797 (eL2), and LC535798 (eL3).
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Jiang, Y., Asuke, S., Vy, T.T.P. et al. Evaluation of durability of blast resistance gene Rmg8 in common wheat based on analyses of its corresponding avirulence gene. J Gen Plant Pathol 87, 1–8 (2021). https://doi.org/10.1007/s10327-020-00967-7
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DOI: https://doi.org/10.1007/s10327-020-00967-7