松果梢斑螟对虫害诱导寄主防御的抑制作用

以松果梢斑螟（Dioryctria pryeri）-油松（Pinus tabuleaformis）（2年生球果和新梢）为研究对象，探讨梢斑螟幼虫对油松球果小卷蛾（Gravitarmata margarotana）先期虫害诱导寄主防御的抑制作用，以及虫害诱导的负防御机制。结果表明，双萜松脂酸作为油松球果和新梢的主要组成和诱导性防御物质，梢斑螟虫害后球果双萜松脂酸极显著增加，10 d后降低到正常水平；而新梢虫害后，松脂酸显著增加，后随新梢基础含量而增加，10 d后虫害新梢松脂酸显著高于球果。梢斑螟幼虫以小卷蛾虫害球果、健康球果和新梢等部位为食料，均为梢斑螟5龄幼虫下唇腺葡萄糖氧化酶（Glucose oxidase，GOX）活性最高，极显著高于4龄和3龄幼虫；且同一龄期，小卷蛾虫害球果中的梢斑螟幼虫GOX活性最高，显著高于新梢和健康球果中幼虫酶活性。研究发现，虫害后萜类防御物质随幼虫GOX活性升高呈下降趋势。梢斑螟幼虫RNA和P含量比较发现，取食小卷蛾虫害球果、健康球果和新梢3种食料，均为梢斑螟3龄幼虫最高，5龄幼虫最小，差异极显著；但同一龄期，3种食料发育的幼虫，其RNA和P含量间无显著差异。这些结果说明，小卷蛾幼虫的先期危害，诱导了寄主防御，但后来的梢斑螟幼虫通过下唇腺GOX抑制了寄主的诱导防御，使其生长率与健康球果和新梢中的幼虫基本一致。

Inhibition of pine coneworm, larvae Dioryctria pryeri, on herbivore-induced defenses of Pinus tabuleaformis

Pine coneworm, Dioryctria pryeri Ragonot (Lepidoptera: Pyalidae), as an important insect pest of the cones and shoots in Chinese pine, Pinus tabuleaformis Mill., tends to select the cones previously damaged by Gravitarmata margarotana (Heinemann) for feeding and oviposition. In the present study, the inhibition of pine coneworm on larvae G. margarotana induced defenses of P. tabuleaformis and mechanism of the herbivore-induced negative defenses was explored in the pine coneworm and Chinese pine (two years old cone and shoot). The result indicated that diterpene resin acid was mainly constructive and induced defense compounds, and it increased significantly in both cones and shoots after damaged by the coneworm. The concentration of resin acid dropped to its normal state after 10 days in the infested cones, whereas it remained in the same high level in the infested shoots after 10 days. We also compared the activity of glucose oxidase (GOX) in salivary gland of larvae D. pryeri among three groups: the cones previously infested by G. margarotana, the cones and shoots. The activity of GOX is significantly higher in the 5^th instars than it in the 4^th and 3^rd instars. In the same instars, the activity of GOX of larvae D. pryeri is the highest in the cones previously infested by G. margarotana group, and the lowest in the shoots group. These result revealed that host terpene defense response was suppressed gradually by the GOX enzyme of pine coneworm. By comparing of the RNA and P content, we found significant difference among the 3^rd, 4^th and 5^th instars. The 3^rd instars had the highest RNA and P content, whereas the 5^th had the lowest. Within the same instars, there was no significant difference in the larvae D. pryeri intake of infested cone by G. margarotana, the cone or shoot. All those results showed that larvae G. margarotana induced host defense responses in the early stage, then larvae D. pryeri suppressed the resin acid defense of Chinese pine by using the GOX enzyme. As the result, there are no significantly difference in the growth rate among the larvae D. pryeri intake of in the cones previously infested by G. Margarotana, the cones and the shoots.