Inglis G D, Lawrence A M, Davis F M
Department of Entomology and Plant Pathology, Mississippi State, MS 39762, USA.
J Econ Entomol. 2003 Feb;96(1):12-20. doi: 10.1603/0022-0493-96.1.12.
A study was undertaken to elucidate the impact of an undescribed Nosema sp. on the southwestern corn borer (SWCB; Diatraea grandiosella Dyar). The Nosema sp. (isolate 506) included in the study was isolated from an overwintering SWCB larva in Mississippi. It was highly infectious per os, with a median infective dose of 2.0 x 10(3) spores per larva. Even at the highest dosage tested (10(7) spores per larva), minimal mortality (< or = 3%) was observed in infected larvae, pupae, and adults reared in the laboratory on an artificial diet. However, infected pupae (0- and 7-d-old) were smaller, and the time to adult eclosion from pupation was slightly increased. Furthermore, the number of eggs produced by infected SWCB female moths substantially decreased (32%), and this effect was most pronounced on day 2, when the greatest number of eggs were oviposited by infected and noninfected moths. For eggs produced by infected females mated with infected males, hatch was slightly decreased by 16 and 15% for eggs laid on days 2 and 3, respectively. In addition, egg hatch was reduced in eggs oviposited by noninfected females mated with infected males on day 3. A low prevalence of infection (< 6%) was observed in the F1 generation originating from infected females mating with noninfected males, from noninfected females mating with infected males, and from infected females mating with infected males. Nosema 506 spores were observed in the proximity of reproductive tissues of infected female and male moths. Spores also were detected on the chorion surface and within eggs laid by infected females. Furthermore, 1-11% of larvae hatching from surface-sterilized eggs were infected by Nosema 506 indicating a transovarial mechanism of transmission.
开展了一项研究，以阐明一种未描述的微孢子虫属物种对西南玉米螟（SWCB；Diatraea grandiosella Dyar）的影响。该研究中包含的微孢子虫属物种（分离株506）是从密西西比州一只越冬的西南玉米螟幼虫中分离出来的。它经口具有高度传染性，每只幼虫的半数感染剂量为2.0×10³个孢子。即使在测试的最高剂量（每只幼虫10⁷个孢子）下，在实验室以人工饲料饲养的受感染幼虫、蛹和成虫中观察到的死亡率也很低（≤3%）。然而，受感染的蛹（0日龄和7日龄）较小，从化蛹到成虫羽化的时间略有增加。此外，受感染的西南玉米螟雌蛾产的卵数量大幅减少（32%），这种影响在第2天最为明显，此时受感染和未受感染的雌蛾产卵数量最多。对于与受感染雄蛾交配的受感染雌蛾产的卵，在第2天和第3天产下的卵孵化率分别略有下降16%和15%。此外，在第3天与受感染雄蛾交配的未受感染雌蛾产的卵孵化率也降低了。在受感染雌蛾与未受感染雄蛾交配、未受感染雌蛾与受感染雄蛾交配以及受感染雌蛾与受感染雄蛾交配产生的F1代中，观察到的感染率较低（<6%）。在受感染雌蛾和雄蛾的生殖组织附近观察到了微孢子虫506孢子。在受感染雌蛾产的卵的卵壳表面和卵内也检测到了孢子。此外，从表面消毒的卵孵化出的幼虫中有1% - 11%被微孢子虫506感染，这表明存在经卵传播机制。
