草地贪夜蛾核型多角体病毒对我国草地贪夜蛾不同地理种群毒力的比较分析

草地贪夜蛾Spodoptera frugiperda（J. E. Smith）入侵我国多个地区，逐渐形成地理种群。在草地贪夜蛾核型多角体病毒Spodoptera frugiperda multiple nucleopolyhedrovirus（SfMNPV）生物农药的生产过程中发现，不同地理来源的宿主对SfMNPV的敏感性和产量存在明显差异，显著影响了SfMNPV的生产效率。为解析其敏感性差异及其产生的原因，本研究首先对云南德宏、广东广州、广西钦州、西藏林芝4个地区草地贪夜蛾种群基因型进行了鉴定，采用生物测定法测试SfMNPV对4龄幼虫的口服毒力，然后，通过向幼虫体内注射草地贪夜蛾核多角体病毒出芽型病毒粒子（budded virions，BVs）的方式，越过口服感染中肠的过程，分析敏感性差异发生的阶段。最后比较了高敏感和低敏感种群中肠肠液pH，并基于16S rDNA测序测定了肠道菌群组成。结果表明，广西种群属于纯合玉米型，其余种群为带有水稻型COI标记的杂合玉米型。广西种群对SfMNPV的口服敏感性最低，西藏种群的敏感性最高，但两者注射BV后死亡率差异无统计学意义，暗示病毒敏感性差异发生在口服感染阶段。广西种群中肠pH略低于西藏种群，并且较于西藏种群，广西种群相肠道乳杆菌Lactobacillus丰度高。本文结果表明，肠道微环境的差异可能是不同地理种群草地贪夜蛾对SfMNPV口服敏感性产生差异的原因。

Comparative analysis of virulence of Spodoptera frugiperda multiple nucleopolyhedrovirus to different geographical populations of Spodoptera frugiperda in China

Spodoptera frugiperda (J. E. Smith) has invaded many regions of China and gradually formed different geographical populations. In order to understand the sensitivity differences of S. frugiperda in different geographical populations to Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV), COI and Tpi molecular markers were used to determine the genotypes of S. frugiperda populations in Dehong in Yunnan, Guangzhou in Guangdong, Qinzhou in Guangxi, and Linzhi in Tibet. Then the oral toxicity of SfMNPV to the 4th instar larvae was tested by bioassay, and the occurrence stage of sensitivity difference was analyzed by injecting budded virus (BVs) into the larvae by passing the oral infection. Finally, the pH of intestinal fluid in highly sensitive and low sensitive populations was compared, and the composition intestinal flora was analyzed based on 16S rDNA sequencing. The results showed that Guangxi population belonged to the homozygous maize type, and the other populations were heterozygous maize types with rice-type COI markers. Guangxi population had the lowest oral sensitivity to SfMNPV, and Tibetan population had the highest oral sensitivity, but there was no significant difference in mortality between the two populations after injection. The midgut pH of Guangxi population was slightly lower than that of Tibet population. Lactobacillus was the dominant bacteria in Guangxi population of S. frugiperda, and Enterococcus was the dominant bacteria in Tibet population. The results of this study suggested that intestinal microenvironment may be the reason for the difference in the sensitivity of S. frugiperda to SfMNPV in different geographical populations.