温度对蚜科专化菌暗孢耳霉休眠孢子形成的影响

Abstract

PDF HTML阅读 XML下载 导出引用 引用提醒 温度对蚜科专化菌暗孢耳霉休眠孢子形成的影响 DOI: 10.5846/stxb201401070048 作者: 作者单位: 浙江农林大学 林业与生物技术学院,浙江农林大学 林业与生物技术学院,浙江农林大学 林业与生物技术学院,浙江农林大学 林业与生物技术学院,浙江农林大学 林业与生物技术学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31300550); 国际科学基金(IFS, C/5146-1) The effect of temperature on in vivo resting spore formation of the aphid-specific pathogen Conidiobolus obscurus Author: Affiliation: Zhejiang Agricultural and Forestry University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探究虫霉休眠孢子形成的关键影响因素,通过孢子浴接种和多浓度生物测定实验,观察蚜科专化菌暗孢耳霉(Conidiobolus obscurus)在5个温度处理(10,15,20,24,28 ℃)和3个接种浓度梯度下感染寄主桃蚜(Myzus persicae)的情况,并观测不同处理下蚜尸内产休眠孢子的比例。暗孢耳霉对桃蚜的毒力随温度和接种浓度升高而提高。同时,感病致死的蚜尸镜检结果表明:温度显著影响休眠孢子形成,温度越高,形成几率越大;接种浓度的影响次之,在15-24 ℃间,形成几率随接种浓度提高而增大。这一现象可能的解释:高温环境将使寄主种群增长停滞或消退,暗孢耳霉通过感知环境温度情况,倾向于在较高温时于寄主体内形成休眠孢子来规避接下来可能出现的寄主匮乏期。 Abstract:Fungi belonging to the order of Entomophthorales are found to induce host epizootics under natural conditions, restraining many agroforestry pest populations below economic damage level. For decades, researchers have focused on exploring these valuable resources with respect to their application in pest biocontrol programs, but the process has proven to be difficult. A poor understanding of the fungal epizootic mechanism and survival strategies in the nature, including the mechanism of in vivo resting spore formation, is one of the main obstacles hindering this effort. Entomophthorales can actively eject numerous conidia to infect nearby hosts, thus transmitting within the host populations. When the host population decreases dramatically, the fungi tend to form thick-walled spores (resting spores, RS) within the bodies of cadavers. Once the conditions improve, RS germinate to restart the infection cycle and regulate the host population. Thus, the RS formation is an important step for fungal survival and the subsequent initiation of the epizootic. Previous reports indicated that many biotic and abiotic factors influence in vivo RS formation, including temperature, humidity, light duration, host age, nutritive conditions, and inoculum levels. However, no consistent conclusion has been formed regarding the vital factors, as contradictory results have been reported for different pathogen-host systems. Temperature and inoculum levels were recently found to exert dominant effects on the formation of Pandora nouryi RS in Myzus persicae inhabiting fields in cold climates. To investigate the main factors influencing in vivo RS formation of the aphid-specific pathogen Conidiobolus obscurus, we performed a series of multi-concentration bioassays of C. obscurus against the host M. persicae under five different temperature treatments (10 ℃, 15 ℃, 20 ℃, 24 ℃, and 28 ℃). The results of the bioassays showed that aphid mortality increased with increasing conidial concentrations used to inoculate the aphids (inoculum level) under each temperature condition. The data were well fitted to the time-concentration-mortality model, and the lowest calculated median lethal concentration (LC50) with 95% confidence intervals was estimated to be 13.6 (11-16.8) conidia/mm2 on day 4 at 28 ℃. Within the crushed cadaver bodies, proportion of the RS formation significantly increased with increased temperature, reaching a peak of 0.66 at 28 ℃. The proportion also increased with inoculum levels at temperatures from 15-24 ℃. Thus, C. obscurus tends to form RS more readily at higher temperatures and inoculum levels. We explain this phenomenon as follows: the rise of temperature to high levels signals the upcoming variation in the host population to C. obscurus, because high temperatures always cause host diapause and population collapse in the fields. For survival in the successive period of host shortage, the fungi tend to form thick-walled RS in host cadavers. Further observation of other entomophthoralean fungi and their hosts is required to verify this prediction. The present results also showed that C. obscurus possesses high infectivity under higher temperature conditions and is thus suitable for aphid control in thefields. 参考文献 相似文献 引证文献