Evaluation of durability of blast resistance gene Rmg8 in common wheat based on analyses of its corresponding avirulence
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Evaluation of durability of blast resistance gene Rmg8 in common wheat based on analyses of its corresponding avirulence gene Yushan Jiang1 · Soichiro Asuke1 · Trinh Thi Phuong Vy1 · Yoshihiro Inoue1,2 · Yukio Tosa1 Received: 4 April 2020 / Accepted: 2 June 2020 © The Phytopathological Society of Japan and Springer Japan KK, part of Springer Nature 2020
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. Keywords Pyricularia oryzae · Magnaporthe oryzae · Ryegrass · Wheat · Avirulence gene
Introduction Pyricularia oryzae (Zhang et al. 2016, syn. Magnaporthe oryzae), a causal agent of blast disease of gramineous plants, consists of several subgroups or pathotypes, each of which is pathogenic on plants with a specific genus, e.g., Oryza (including rice), Setaria (including foxtail millet), or The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession numbers, LC535796 (eL1), LC535797 (eL2), and LC535798 (eL3). Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10327-020-00967-7) contains supplementary material, which is available to authorized users. * Yukio Tosa tosayuki@kobe‑u.ac.jp 1
Laboratory of Plant Pathology, Graduate School of Agricultural Science, Kobe University, Nada, Kobe 657‑8501, Japan
Present Address: The Sainsbury Laboratory, Norwich NR4 7UH, UK
2
Eleusine (including finger millet) (Kato et al. 2000). This fungus also has the potential to cause destructive epidemics on plant genera that have not been known as its primary hosts and has evolved new pathotypes. One example is the evolution
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