Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA.
United States Department of Agriculture-Agricultural Research Service, Crops Pathology and Genetics Research Unit, Davis, CA 95616, USA.
Environ Entomol. 2021 Aug 12;50(4):948-957. doi: 10.1093/ee/nvab038.
Plant structural traits can act as barriers for herbivore attachment, feeding, and oviposition. In particular, epicuticular waxes (EWs) on the aerial surfaces of many land plants offer protection from biotic and abiotic stresses. In rice (Oryza sativa L.), mutations that reduce EWs have been previously reported. However, whether such mutations affect rice water weevil (Lissorhoptrus oryzophilus Kuschel) and fall armyworm (Spodoptera frugiperda Smith) performance has not been investigated yet. These pests cause significant economic problems in important rice-producing areas of the United States. The aim of our study was to characterize the EWs of EW mutants and wild-type rice plants by gas chromatography-mass spectrometry and compare the resistance of mutant and wild-type plants against rice water weevil and fall armyworm. We hypothesized that mutants with reduced EWs would have weaker resistance to pests than wild-type plants. Three mutant lines (6-1A, 7-17A, and 11-39A) and their wild-type parent (cv. 'Sabine') were used to test this hypothesis. Levels of EWs were significantly lower in mutant lines than in the wild-type, and qualitative differences in EW composition were also observed. Reduction in EWs significantly affected performance of insects in experiments conducted under greenhouse conditions. Experiments with rice water weevils were conducted in arenas in which females were given a choice of the mutants and the wild-type for oviposition. Number of first instars emerging from the three EW mutants (an indication of oviposition preference) was higher on the three EW mutants than on wild-type plants with normal wax levels. Similarly, in no-choice experiments using whole plants or detached leaves, weight gains of armyworms on leaves were higher on the mutant lines than on the wild-type. These results indicate that EW traits are involved in rice resistance to weevils and armyworms. Understanding the plant traits that contribute to resistance to rice pests will be helpful for the development of resistant varieties for reducing pest insect damage.
植物的结构特征可以作为阻碍草食动物附着、进食和产卵的屏障。特别是，许多陆生植物的气生表面上的表皮蜡（EWs）提供了对生物和非生物胁迫的保护。在水稻（Oryza sativa L.）中，已经报道了减少 EWs 的突变。然而，这种突变是否会影响水稻水象甲（Lissorhoptrus oryzophilus Kuschel）和秋粘虫（Spodoptera frugiperda Smith）的性能尚未得到研究。这些害虫在美国重要的水稻产区造成了重大的经济问题。我们研究的目的是通过气相色谱-质谱法来描述 EW 突变体和野生型水稻植株的 EWs，并比较突变体和野生型植株对水稻水象甲和秋粘虫的抗性。我们假设，EWs 减少的突变体对害虫的抗性比野生型植株弱。使用三个突变体系（6-1A、7-17A 和 11-39A）及其野生型亲本（品系 'Sabine'）来检验这一假设。突变体系的 EWs 水平明显低于野生型，并且观察到 EW 组成的定性差异。在温室条件下进行的实验中，EWs 的减少显著影响了昆虫的表现。与秋粘虫进行的实验是在竞技场中进行的，雌性可以在突变体和野生型之间选择产卵。从三个 EW 突变体中出现的第一龄幼虫数量（表明产卵偏好）在三个 EW 突变体上高于具有正常蜡水平的野生型植物。同样，在使用整株植物或离体叶片的非选择实验中，秋粘虫在叶片上的增重也高于野生型。这些结果表明，EW 特征参与了水稻对象甲和粘虫的抗性。了解有助于提高水稻对害虫抗性的植物特征将有助于开发抗虫品种，以减少害虫昆虫的损害。
