Department of Plant Pathology and Weed Research, Agricultural Research Organization, Volcani Center, Rishon LeZion, Israel.
Department of Entomology, Nematology and Chemistry Units, Agricultural Research Organization, Volcani Center, Rishon LeZion, Israel.
Pest Manag Sci. 2021 May;77(5):2557-2567. doi: 10.1002/ps.6294. Epub 2021 Feb 4.
Intensive application of chemical insecticides is required for aphid pest control. Among the biorational alternatives, entomopathogenic fungi are the most sustainable biocontrol agents; those of the order Hypocreales attack and cause fungal disease in arthropod hosts, with variations in host susceptibility attributed to both fungal and host characteristics. We evaluated inter- and intraspecies variations in Metarhizium spp. virulence and differences in fungal disease progression on adult and nymph stages of the green peach aphid, Myzus persicae (Sulzer), a parthenogenetically reproducing insect species.
Minor interspecies diversity was detected between the generalist Metarhizium species examined. Interestingly, significant intraspecies diversity was observed between Metarhizium brunneum isolates Mb7 and MbK. Infected adult aphids demonstrated similar disease progression for both isolates, mortality rates of more than 80% and fivefold reduction in fecundity. However, nymph mortality was detected only following MbK infection, with 50% mortality and significant reduction in molting rates. Confocal laser scanning microscopy demonstrated the variation in the disease stages of conidial adhesion and hemocoel colonization on each examined day post inoculation for each isolate. Significantly faster disease progression was observed in MbK-infected versus Mb7-infected nymphs, the latter demonstrating a higher percentage of uninfected nymphs accompanied with aphid molting.
The observed intraspecies variation suggests that altered conidial adhesion to the nymph cuticle is a major factor affecting virulence. We prove the role of nymph ecdysis as a defense mechanism disrupting fungal infection. Because significant differences were observed between closely related isolates, this study emphasizes the importance of appropriate isolate selection for biological control. © 2021 Society of Chemical Industry.
防治蚜虫虫害需要大量使用化学杀虫剂。在各种生物防治替代方法中，病原真菌是最可持续的生物防治剂；那些属于子囊菌门的真菌会攻击并引起节肢动物宿主的真菌感染，宿主易感性的变化归因于真菌和宿主的特征。我们评估了绿桃蚜（Myzus persicae （Sulzer））成虫和若虫阶段的病原真菌多样性以及病原真菌致病力的变化。
在所研究的一般性病原真菌中，种间多样性差异较小。有趣的是，在病原真菌白僵菌 Mb7 和 MbK 之间观察到显著的种内多样性。感染的成年蚜虫在两个分离株上表现出相似的疾病进展，死亡率超过 80%，繁殖力降低五倍。然而，只有在感染 MbK 后才会检测到若虫死亡，死亡率为 50%，蜕皮率显著降低。共聚焦激光扫描显微镜显示，在每个接种后检查日，每个分离株的分生孢子附着和血腔定殖的疾病阶段存在差异。在 MbK 感染的若虫中观察到更快的疾病进展，而在 Mb7 感染的若虫中，未感染的若虫比例更高，伴随着蚜虫蜕皮。
观察到的种内变异表明，分生孢子对若虫表皮的附着改变是影响致病力的主要因素。我们证明了若虫蜕皮作为一种破坏真菌感染的防御机制的作用。由于在密切相关的分离株之间观察到显著差异，因此本研究强调了为生物防治选择适当分离株的重要性。 © 2021 化学工业学会。
