Consequences of interspecific competition on the virulence and genetic composition of a nucleopolyhedrovirus in Spodoptera frugiperda larvae parasitized by Chelonus insularis
Consequences of interspecific competition on the virulence and genetic composition of a nucleopolyhedrovirus in Spodoptera frugiperda larvae parasitized by Chelonus insularis
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DOI：
10.1080/09583150120076193
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发表时间：
2001-09-01
影响因子：
1.4
通讯作者：
Caballero, P
中科院分区：
文献类型：
--
作者：
Escribano, A;Williams, T;Caballero, P
核型多角体病毒（杆状病毒科）是一种具有高度宿主特异性的昆虫病原体，具有生物杀虫剂的潜力。每当病毒用于害虫防治时，一部分受感染的昆虫也会被hyperteran或dipteran寄生蜂寄生，并且会发生种间对宿主资源的竞争;这种竞争的严重程度很可能在很大程度上受到每种寄生虫毒力的调节。我们研究了寄生的影响，由单独的卵幼虫endoparasitoid龟鳖insularis（Hyattera：茧蜂科）的速度杀死的核型多角体病毒感染的草地贪夜蛾（鳞翅目：夜蛾科）幼虫和宿主生长和病毒生产的模式在感染和/或寄生的主机。我们还研究了寄生对连续传代病毒的毒力、感染性和遗传组成的影响。寄生和病毒感染都导致宿主生长显著减少。当三龄幼虫被双重寄生和病毒感染时，与被寄生的幼虫相比，生长速率受到更严重的影响。有一个显着的增加，病毒生产的幼虫感染后龄期。种间竞争导致在第四龄感染的寄生幼虫的病原体产量大幅下降，但在早期感染的寄生幼虫。连续传代实验导致通过限制性内切酶分析检测到病毒的四种不同遗传分离株的出现。出现在nonparasitized幼虫的三个分离株，两个表现出增加的毒力，平均死亡时间表示，其中之一的感染性，表示为LC 50，减少。一个出现在寄生幼虫中的分离物（分离物D）具有增强的毒力和感染性。Southern印迹分析表明，病毒分离株D最有可能是通过限制性位点的点突变或通过改变（如复制、缺失）或通过野生型核型多角体病毒分离株中存在的两种或多种基因型变体的重组产生的。我们的研究提供了宿主内种间竞争的明确证据，因为，根据接种的时间，观察到的寄生蜂和病毒的不利影响。
Nucleopolyhedroviruses (Baculoviridae) are virulent insect pathogens that generally show a high degree of host specificity and have recognized potential as biological insecticides. Whenever viruses are applied for pest control, a proportion of the infected insects will also be parasitized by hymenopteran or dipteran parasitoids and interspecific competition for host resources will occur; the severity of such competition is likely to be modulated to a large degree by the virulence of each type of parasite. We examined the impact of parasitism by the solitary egg-larval endoparasitoid Chelonus insularis (Hymenoptera: Braconidae) on the speed of kill of nucleopolyhedrovirus-infected Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae and the pattern of host growth and virus production in infected and/or parasitized hosts. We also examined the effect of parasitism on the virulence, infectivity and genetic composition of serially passaged virus. Both parasitism and viral infection resulted in a marked reduction in host growth. When third instar larvae were dually parasitized and virus-infected, the growth rate was even more severely affected compared to parasitized larvae. There was a significant increase in virus production in larvae infected at later instars. Interspecific competition resulted in a substantial decrease in pathogen production in parasitized larvae infected at the fourth instar, but not in parasitized larvae infected at earlier instars. The serial passage experiment resulted in the appearance of four distinct genetic isolates of the virus detected by restriction endonuclease analysis. Of the three isolates that appeared in nonparasitized larvae, two showed increased virulence, expressed by mean time to death, and for one of these the infectivity, expressed as LC50, was reduced. One isolate that appeared in parasitized larvae (isolate D) had increased virulence and infectivity. Southern blot analysis indicated that virus isolate D was most likely generated by point mutation of a restriction site or by alterations such as duplications, deletions or by recombination of two or more genotypic variants present in the wild-type nucleopolyhedrovirus isolate. Our study provides clear evidence of interspecific competition within the host, since, depending on the timing of inoculation, adverse effects were observed upon both the parasitoid and the virus.