草地螟幼虫密度依赖的抗病性机制研究

免疫功能在昆虫密度依赖的抗病性中起重要作用，但是有关密度依赖的免疫功能变化机制至今仍不清楚。已有证据表明，单胺能调节昆虫的免疫反应，且其含量变化与种群密度有关。这为揭示昆虫密度依赖的抗病性机制提供了重要思路。本项目在明确草地螟存在密度依赖的抗病性基础上，测定不同密度草地螟幼虫单胺（章鱼胺、五羟色胺、多巴胺）含量和免疫指标（血细胞总数、包囊作用、酚氧化酶和溶菌酶活性及其基因mRNA表达量）的变化，探明幼虫密度、单胺含量及免疫指标之间的关系；结合幼虫注射外源单胺测定其对球孢白僵菌的抵抗能力及其免疫指标的变化，明确单胺对幼虫抗病性的调节作用；通过室外网罩设置不同密度草地螟幼虫的抗病能力测定，进一步证实草地螟幼虫密度依赖的抗病性现象。通过以上研究阐明草地螟幼虫密度依赖的抗病性机制，为从昆虫密度依赖的抗病性角度探索种群暴发机制提供新的思路。

Immune function play an important role in the density-dependent resistance to disease in insects, but the resistance mechanism is still unclear. It has been suggested that some monamine modulate immune reactions and the varying of its content is related to population density. This provided an important clue to understand the immune mechanism of the insect density-dependent disease resistance. The density-dependent disease resistance has been proved in the meadow moth. In this study, the content of monamine(octopamine, 5-hydroxytryptamine, dopamine), the immune indicators (total hemocyte counts, encapsulation response, activities and mRNA expression level of prophenoloxidase and lysozyme genes) will be measured in the larvae from different densities. These will clarify the relationships among larval density，the content of monamine and the immune indicators The disease resistance of the larvae to Beauveria bassiana will be also tested after injection of monamine. The regulation of monamine on the larval density-dependent disease resistance will be analysed. The disease resistance of the different larval densities of meadow moth will be also determined in outdoor net tests, further verifying the meadow moth larvae density-dependent disease resistance phenomenon. This will illuminate the mechanism of insect density-dependent disease resistance, and provide novel evidence to elucidate the mechanism of meadow moth outbreaks.