重要林木害虫木毒蛾主要成灾寄主树种变化的机制

The casuarina moth, Lymantria xylina is a major pest in Fujian and Taiwan province mainly damages Casuarina plants in coastal protection forest on both sides of the Taiwan Straits. Since outbreak of Lymantria xylina in Euphoria longana forest was reported, its host plant has expanded. However, the selection of the moth between these two plants was still not clear. Therefore our research focuses on effect of host switching on development and host selection of Lymantria xylina. In this study, two populations of casuarina moth from casuarina and longan were fed with casuarina plants and longan plants separately, leading to 4 treatment groups by simulation of host switching to study 1) effect of the two host plant and host switching on the development; 2) nutrients and secondary substances differences between the two plants, and its relationship of eating choice, host location, and oviposition; 3) expression level changes of P450s in the 4th instar among different treatment groups. By analyzing the key factor of the host selection behavior, and the adaption of the moth associated with the related elements, to reveal the mechanism of host switching. Our research will provide a valuable reference in assessment, monitoring and ecological regulation programs of the disaster.

木毒蛾是海峡两岸沿海防护林木麻黄的首要害虫。近年来突然发现该虫害在龙眼林内暴发，木毒蛾主要成灾寄主树种从木麻黄扩展到龙眼，但是该虫在两种寄主之间如何选择尚不明确。针对这一问题，本项目重点研究寄主变化前后木毒蛾生长发育及寄主选择行为的差异。以木麻黄和龙眼林内的木毒蛾种群为研究对象，模拟寄主转换过程，同时分别喂食两个种群木麻黄和龙眼枝叶，共计4组处理，研究1）不同寄主及寄主转换对木毒蛾生长发育的影响，2）寄主营养物质和次生物质差异，以及这些差异与寄主转换前后木毒蛾幼虫取食选择、成虫寄主定位产卵行为的相关性，3）交互试验获得的木毒蛾暴食期4龄幼虫的P450解毒代谢基因表达差异等内容，分析木毒蛾寄主选择差异的关键因素，及其对相关因子的适应，揭示木毒蛾成灾寄主变化的内在机制，为该害虫的发生评估、监测和生态调控提供指导。

近年来木毒蛾主要成灾寄主树种从木麻黄扩展到龙眼，但是该虫在两种寄主之间如何选择尚不明确。针对这一问题，本项目首先确定了研究区内木毒蛾主要寄主26个常见木麻黄品系的亲缘关系，福建省内的木麻黄品系从属关系不明确，但是可以分为三大类群，和印度、埃及、肯尼亚品系比较靠近。同时测定了世界范围内的木毒蛾不同地理种群的基因多样性，发现中国湖北和重庆的木毒蛾种群与其它地区的木毒蛾种群存在一定的分化。本项目重点研究了福建省内寄主变化对木毒蛾生长发育及解毒代谢基因的影响，首先明确了试验区内木毒蛾幼虫龄期为7龄，取食龙眼的木毒蛾幼虫发育历期明显短于木麻黄种群，小于木麻黄种群的一半，低龄（1-4龄）龙眼种群幼虫体长显著长于木麻黄种群，木麻黄种群高龄幼虫（6、7龄）发育历期较长，体长也较长。龙眼种群和木麻黄种群相比，下调基因387个，主要集中于氧化还原过程；上调基因336个，主要集中于代谢进程和有机物新陈代谢。木毒蛾龙眼种群和木麻黄种群相比，共有6个P450基因发生上调（3个）和下调（3个）改变，共得到P450基因全长5条，5个基因的定量验证结果与转录组数据变化趋势相同。同时，本项目对木毒蛾幼虫Bt受体APN基因和CAD基因进行了克隆和表达，明确了不同龄期和部位的表达差异。同时，还明确了雌雄触角的感受器差异和气味受体OBP基因的差异，这些差异基因在该害虫的生态调控中具有潜在的利用价值。