Chiozza Mariana V, O'Neal Matthew E, MacIntosh Gustavo C
Department of Entomology, Iowa State University, Ames, IA 50011-3140, USA.
Environ Entomol. 2010 Jun;39(3):856-64. doi: 10.1603/EN09338.
Although soybean aphid (Aphis glycines) resistance is commercially available in the form of the Rag1 gene, the mechanism of this resistance is not fully understood. Amino acids are a limiting factor for aphid growth, and there is evidence that plant amino acid composition is related to aphid resistance. Antibiotic resistance like that conferred by Rag1 could be associated in part with both protein and nonprotein free amino acids reducing survival, growth, and fecundity of the target pest. We posed two hypotheses: (1) A. glycines resistance is related to host quality in terms of free amino acids composition in the leaf, and (2) aphids may enhance host quality by inducing changes in the free amino acids composition. To test these hypotheses we conducted a field experiment using a split plot design, with soybean lines (a susceptible line and a related line carrying Rag1) as whole plots and aphid density as subplots (insecticide treated or left exposed to natural infestations). We analyzed free amino acids in leaves at three soybean developmental stages in all subplots. We observed significant whole and subplot effects on the concentration of a subset of amino acids tested. Susceptible and resistant plants had constitutive (whole-plot) differences in amino acids composition in all developmental stages analyzed. In addition, aphid-induced (subplot) responses of the plant to aphid infestation were found. We propose that the reduced nutritional quality of the resistant line and its reduced susceptibility to aphid-induced changes may contribute to aphid resistance conferred by Rag1.
尽管大豆蚜（Aphis glycines）抗性是以Rag1基因的形式商业化可得，但这种抗性的机制尚未完全了解。氨基酸是蚜虫生长的限制因素，并且有证据表明植物氨基酸组成与蚜虫抗性有关。像Rag1赋予的那种抗生性可能部分与蛋白质和非蛋白质游离氨基酸降低目标害虫的存活率、生长和繁殖力有关。我们提出了两个假设：（1）大豆蚜抗性在叶片游离氨基酸组成方面与寄主质量有关，（2）蚜虫可能通过诱导游离氨基酸组成的变化来提高寄主质量。为了检验这些假设，我们采用裂区设计进行了一项田间试验，将大豆品系（一个感虫品系和一个携带Rag1的相关品系）作为主区，蚜虫密度作为副区（用杀虫剂处理或任其自然侵染）。我们分析了所有副区中三个大豆发育阶段叶片中的游离氨基酸。我们观察到对所测试的一部分氨基酸浓度有显著的主区和副区效应。在所有分析的发育阶段，感虫和抗性植株在氨基酸组成上存在组成型（主区）差异。此外，还发现了植物对蚜虫侵染的蚜虫诱导（副区）反应。我们提出，抗性品系营养质量的降低及其对蚜虫诱导变化的敏感性降低可能有助于Rag1赋予的蚜虫抗性。
