Laboratory of Plant Pathology, Graduate School of Agricultural Sciences, Kobe University, Nada, Kobe 657-8501, Japan.
Genome. 2009 Sep;52(9):801-9. doi: 10.1139/g09-054.
Common wheat cultivars are resistant to Magnaporthe grisea, a crabgrass (Digitaria sanguinalis)-specific species of the blast fungus. To dissect the genetic basis of this "nonhost" type of resistance, we need an exceptional cultivar that is susceptible to M. grisea. A screening under various conditions revealed that Triticum aestivum 'Chinese Spring' (CS) was susceptible to M. grisea isolate Dig41 when incubated at high temperature (26 degrees C) after inoculation. By contrast, T. aestivum 'P168', 'Shin-chunaga' (Sch), 'Norin 4' (N4), 'Norin 26' (N26), 'Norin 29' (N29), 'Red Egyptian' (RE), and 'Salmon' (Slm) and Triticum compactum 'No. 44' (Cmp) were highly resistant even at the high temperature. When F2 seedlings derived from crosses between the resistant cultivars and CS were inoculated with Dig41, they segregated in a 3:1 ratio of resistant to susceptible, suggesting that the resistance of each cultivar is controlled by one major gene. Crosses of N4 with P168, Sch, N26, N29, and Cmp yielded no susceptible F2 seedlings, suggesting that these six cultivars share the same gene. Similarly, a cross between RE and Slm yielded no susceptible F2 seedlings, suggesting that these two cultivars share the same gene. On the other hand, crosses between the N4 group and the RE group produced resistant and susceptible seedlings in a 15:1 ratio, indicating that these two groups carry different genes inherited independently. The gene in N4 was located on chromosome 4A by a monosomic analysis and designated Rmg4, while the gene in RE was located on chromosome 6D using a series of chromosome substitution lines and designated Rmg5. These results suggest that the resistance of common wheat to M. grisea, an inappropriate species of the blast fungus, is under a simple genetic control.
普通小麦品种对稻瘟病菌（Magnaporthe grisea）具有抗性，稻瘟病菌是一种专门感染稗草（Digitaria sanguinalis）的炭疽病菌。为了剖析这种“非寄主”类型抗性的遗传基础，我们需要一种易感染稻瘟病菌的特殊品种。通过在各种条件下进行筛选，我们发现普通小麦品种 Chinese Spring（CS）在接种后高温（26°C）下易感染稻瘟病菌 Dig41。相比之下，T. aestivum 'P168'、'Shin-chunaga'（Sch）、'Norin 4'（N4）、'Norin 26'（N26）、'Norin 29'（N29）、'Red Egyptian'（RE）和'Salmon'（Slm）以及 Triticum compactum 'No. 44'（Cmp）即使在高温下也具有高度抗性。当将来自抗性品种与 CS 杂交的 F2 幼苗用 Dig41 接种时，它们以抗性与易感的 3:1 比例分离，表明每个品种的抗性由一个主要基因控制。N4 与 P168、Sch、N26、N29 和 Cmp 的杂交没有产生易感的 F2 幼苗，表明这六个品种共享相同的基因。同样，RE 和 Slm 的杂交也没有产生易感的 F2 幼苗，表明这两个品种共享相同的基因。另一方面，N4 组和 RE 组之间的杂交产生了抗性和易感的幼苗，比例为 15:1，表明这两个组携带独立遗传的不同基因。N4 中的基因通过单体分析定位在 4A 染色体上，命名为 Rmg4，而 RE 中的基因则使用一系列染色体替代系定位在 6D 染色体上，命名为 Rmg5。这些结果表明，普通小麦对稻瘟病菌（Magnaporthe grisea）的抗性是由简单的遗传控制的，稻瘟病菌是一种不适当的炭疽病菌种。
