Pyramiding resistance genes is predicted to increase the durability of resistant rice varieties against phloem-feeding herbivores. We examined responses by the green leafhopper, Nephotettix virescens (Hemiptera: Cicadellidae), to near-isogenic rice lines with zero, one and two resistance genes. The recurrent parent (T65) and monogenic lines (GRH2-NIL and GRH4-NIL) with genes for resistance to the green rice leafhopper, Nephotettix cincticeps (Hemiptera: Cicadellidae), were susceptible to the green leafhopper, but the pyramided line (GRH2/GRH4-PYL) was highly resistant to the green leafhopper. We selected green leafhoppers, N. virescens, from five sites in the Philippines for over 20 generations on each of the four lines. Populations selected on GRH2/GRH4-PYL gained partial virulence (feeding and development equal to that on T65) to the pyramided line within 10 generations and complete virulence (egg-laying equal to that on T65) within 20 generations. After 20 generations of rearing on the susceptible monogenic lines, green leafhoppers were also capable of developing and laying eggs on GRH2/GRH4-PYL. Furthermore, green leafhoppers reared on the susceptible GRH4-NIL for 20 generations showed equal preferences for T65 and GRH2/GRH4-PYL in choice bioassays. Our results indicate that previous long-term exposure to ineffective genes (including unperceived resistance genes) could dramatically reduce the durability of pyramided resistance. We suggest that informed crop management and deployment strategies should be developed to accompany rice lines with pyramided resistance and avoid the build-up of virulent herbivore populations.

中文翻译：

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稻叶蝉的毒力适应：暴露于无效基因会损害金字塔抗性

金字塔抗性基因预计将提高抗性水稻品种对韧皮部食草动物的耐受性。我们检测了绿叶蝉 Nephotettix virescens（半翅目：叶蝉科）对带有零个、一个和两个抗性基因的近等基因水稻品系的反应。具有抗绿叶蝉基因的轮回亲本 (T65) 和单基因品系 (GRH2-NIL 和 GRH4-NIL) 对绿叶蝉敏感，但金字塔品系 (GRH2/ GRH4-PYL) 对绿叶蝉具有高度抗性。我们从菲律宾的五个地点选择了绿叶蝉（N. virescens），在四个品系中每个品系都有 20 代以上。在 GRH2/GRH4-PYL 上选择的群体在 10 代内获得对金字塔系的部分毒力（摄食和发育与 T65 相同），并在 20 代内获得完全毒力（产卵与 T65 相同）。在易感单基因系上饲养20代后，绿叶蝉也能够在GRH2/GRH4-PYL上发育并产卵。此外，在易感GRH4-NIL上饲养20代的绿叶蝉在选择生物测定中对T65和GRH2/GRH4-PYL表现出相同的偏好。我们的结果表明，之前长期接触无效基因（包括未被察觉的抗性基因）可能会显着降低金字塔抗性的持久性。我们建议应制定明智的作物管理和部署策略，以配合具有金字塔抗性的水稻品系，并避免有毒草食动物种群的积累。