Centro Internacional de Agricultura Tropical, CIAT, Apartado Aéreo 6713, Cali, Colombia.
J Econ Entomol. 2010 Oct;103(5):1860-5. doi: 10.1603/ec10004.
Both nymphal and adult spittlebugs (Hemiptera: Cercopidae) cause serious economic damage to susceptible brachiariagrass [genus Brachiaria (Trin.) Griseb], pastures in tropical America. Both life stages are xylem feeders: nymphs feed primarily on roots and stems, whereas the adults feed mainly on foliage. Numerous interspecific brachiariagrass hybrids with high levels of antibiosis resistance to nymphs of several important spittlebug species have been obtained. Recent studies revealed major inconsistencies between reaction to nymphs and reaction to adults on the same host genotype. Because both insect life stages can cause severe economic damage on susceptible brachiariagrass pastures, a cultivar development strategy must take into account resistance to both life stages. To assess the degree of association between resistance to spittlebug nymphs and to adult feeding, we tested 164 hybrids and six check genotypes for resistance to both life stages of three spittlebug species: Aeneolamia varia (F.), Aeneolamia reducta (Lallemand), and Zulia carbonaria (Lallemand). Most hybrids tested were classified as resistant to nymphs. On the contrary, for all three species, the overall mean damage score of the 164 hybrids did not differ from the mean score of the susceptible checks. None of the hybrids was classified as resistant to adult feeding damage. Correlations between percentage nymph survival and adult damage scores were consistently low (r = 0.0104-0.0191). Correlations between nymphal and adult damage scores were also low (0.109-0.271), suggesting that resistances to the different life stages are largely independent. Chi-square analyses comparing frequency distributions of responses of the 164 breeding hybrids to nymphs or adults confirmed essential genetic independence of these two traits. We conclude that attention to improving genetic resistance specifically to adult feeding damage is warranted.
若虫和成虫沫蝉（半翅目：沫蝉科）都会对美洲热带地区的脆弱臂形草（臂形草属（Trin.）Griseb.）牧草造成严重的经济损失。两个生命阶段都是木质部取食者：若虫主要以根和茎为食，而成虫主要以叶片为食。已经获得了许多具有高水平抗生性的种间臂形草杂交种，对几种重要沫蝉若虫具有抗性。最近的研究表明，同一宿主基因型对若虫的反应与对成虫的反应之间存在重大不一致。由于两种昆虫的生命阶段都会对易感的臂形草牧场上造成严重的经济损失，因此必须在品种发展策略中考虑对两个生命阶段的抗性。为了评估对沫蝉若虫和成虫取食的抗性之间的关联程度，我们测试了 164 个杂交种和 6 个对照基因型对 3 种沫蝉（Aeneolamia varia（F.）、Aeneolamia reducta（Lallemand）和 Zulia carbonaria（Lallemand））的两个生命阶段的抗性。测试的大多数杂交种被归类为对若虫具有抗性。相反，对于所有 3 个物种，164 个杂交种的总体平均损伤评分与易感对照的平均评分没有差异。没有一个杂交种被归类为对成虫取食损伤具有抗性。若虫存活率与成虫损伤评分之间的相关性一直很低（r = 0.0104-0.0191）。若虫和成虫损伤评分之间的相关性也很低（0.109-0.271），表明对不同生命阶段的抗性在很大程度上是独立的。比较 164 个杂交种对若虫或成虫的反应频率分布的卡方分析证实了这两个性状的遗传独立性。我们得出的结论是，值得关注的是提高对成虫取食损伤的遗传抗性。
