First, second, third, fourth, fifth, and eighth authors: Graduate School of Agricultural Sciences, Kobe University, Kobe 657-8501, Japan; sixth author: The Sainsbury Laboratory, Norwich Research Park, Norwich NR4 7UH, UK; and seventh author: Graduate School of Environmental and Life Science, Okayama University, Okayama 700-8530, Japan.
Phytopathology. 2018 Nov;108(11):1299-1306. doi: 10.1094/PHYTO-12-17-0400-R. Epub 2018 Sep 11.
The wheat blast fungus (Triticum pathotype of Pyricularia oryzae) first arose in Brazil in 1985 and has recently spread to Asia. Resistance genes against this new pathogen are very rare in common wheat populations. We screened 520 local landraces of common wheat collected worldwide with Br48, a Triticum isolate collected in Brazil, and found a highly resistant, unique accession, GR119. When F seedlings derived from a cross between GR119 and Chinese Spring (CS, susceptible control) were inoculated with Br48, resistant and susceptible seedlings segregated in a 15:1 ratio, suggesting that GR119 carries two resistance genes. When the F seedlings were inoculated with Br48ΔA8 carrying a disrupted allele of AVR-Rmg8 (an avirulence gene corresponding to a previously reported resistance gene, Rmg8), however, the segregation fitted a 3:1 ratio. These results suggest that one of the two genes in GR119 was Rmg8. The other, new gene was tentatively designated as RmgGR119. GR119 was highly resistant to all Triticum isolates tested. Spikes of GR119 were highly resistant to Br48, moderately resistant to Br48ΔA8 and a hybrid culture carrying avr-Rmg8 (nonfunctional allele), and highly resistant to its transformant carrying AVR-Rmg8. The strong resistance of GR119 was attributed to the combined effects of Rmg8 and RmgGR119.
小麦印度腥黑穗病菌（稻柄型球腔菌）于 1985 年首次在巴西出现，最近已传播到亚洲。普通小麦种群中针对这种新病原体的抗性基因非常罕见。我们用在巴西采集的小麦分离物 Br48 对全球收集的 520 份普通小麦地方品种进行了筛选，发现了一个高度抗性的独特品种 GR119。当从 GR119 和中国春（敏感对照）杂交的 F1 幼苗用 Br48 接种时，抗性和敏感幼苗以 15:1 的比例分离，表明 GR119 携带两个抗性基因。然而，当用携带 AVR-Rmg8 （一个与先前报道的抗性基因 Rmg8 对应的无毒基因）缺失等位基因的 Br48ΔA8 接种 F1 幼苗时，分离符合 3:1 的比例。这些结果表明，GR119 中的两个基因之一是 Rmg8。另一个新基因暂命名为 RmgGR119。GR119 对所有测试的小麦分离物均具有高度抗性。GR119 的穗部对 Br48 高度抗性，对 Br48ΔA8 和携带 avr-Rmg8（无功能等位基因）的杂种培养物中度抗性，对携带 AVR-Rmg8 的转化体高度抗性。GR119 的强抗性归因于 Rmg8 和 RmgGR119 的共同作用。
