Govindarajan R, Federici B A
Department of Entomology, University of California, Riverside 92521.
J Invertebr Pathol. 1990 Nov;56(3):291-9. doi: 10.1016/0022-2011(90)90115-m.
The infectivity per os and by inoculation of ascoviruses isolated from Heliothis zea, Spodoptera frugiperda, and Trichopulsia ni and the effects of infection by these viruses on host growth and development were studied in the species from which these viruses were originally isolated, or in the case of the H. zea isolate, in H. virescens. Mortality caused by all three viral isolates averaged less than 15% in third instars fed doses of 10 to 10(5) viral vesicles per larva incorporated into diet, whereas inoculation with as few as 10 viral vesicles consistently yielded mortality rates greater than 90%. In tests where groups of 10 larvae were inoculated sequentially with a minuten pin that had been inserted into the hemocoel of an infected larva and then dried for up to 24 hr, mortality rates were consistently greater than 90%. The latter results suggest that ascoviruses in the field may be vectored by insect parasites. The studies of the effects of infection on larval growth and development demonstrated a marked loss of appetite and a decrease in weight gain within 24-48 hr of infection in all three isolates. Third instars inoculated at a weight of ca. 15 mg gained little weight after infection and had difficulty molting, but survived in an arrested state of development for 2-5 weeks. Controls pupated within 5-7 days after attaining weights, depending on the host species, in the range of 300-500 mg. Arrested development and lack of weight gain appear to be due to decreased feeding, whereas the long survival of infected larvae is likely due to the limited destruction of host tissues.
研究了从玉米螟、草地贪夜蛾和粉纹夜蛾中分离出的 ascoviruses 的经口感染性和接种感染性，以及这些病毒感染对其最初分离物种宿主生长和发育的影响；对于从玉米螟中分离出的病毒，研究了其对绿铃夜蛾的影响。给三龄幼虫喂食每只幼虫含 10 至 10(5)个病毒囊泡的饲料，这三种病毒分离株导致的死亡率平均低于 15%，而接种低至 10 个病毒囊泡的死亡率始终高于 90%。在试验中，用插入感染幼虫血腔后干燥长达 24 小时的微小针依次接种 10 只幼虫的组，死亡率始终高于 90%。后一结果表明，田间的 ascoviruses 可能由昆虫寄生虫传播。感染对幼虫生长和发育影响的研究表明，所有三种分离株在感染后 24 - 48 小时内均出现明显的食欲丧失和体重增加减少。体重约 15 毫克时接种的三龄幼虫感染后体重几乎没有增加，且蜕皮困难，但在发育停滞状态下存活 2 - 5 周。对照组在体重达到 300 - 500 毫克范围内（取决于宿主物种）后 5 - 7 天化蛹。发育停滞和体重不增加似乎是由于摄食减少，而感染幼虫的长期存活可能是由于宿主组织的有限破坏。
