Abstract Fungi in the genus Metarhizium (Hypocreales: Clavicipitaceae) are entomopathogens that can establish as endophytes and benefit their host plant through growth promotion and suppression of insect pests. This study focuses on the Metarhizium-insect-plant interactions in greenhouse- and lab-based experiments. We inoculated seeds of maize (Zea mays L.) with spores of Metarhizium robertsii and evaluated V4 maize for endophytic colonization of leaves and roots, measured plant height, chlorophyll content and above-ground biomass, and relative growth rate of black cutworm, Agrotis ipsilon (Hufnagel). In addition, we studied the expression of selected plant defense genes. We recovered M. robertsii from 91% of plants grown from inoculated seeds. We detected M. robertsii more frequently in roots compared with leaves. Colonized plants were greater in plant height and above-ground biomass compared to control plants. Leaf tissue from colonized plants showed changes in the expression of genes involved in plant defense. In feeding bioassays, the relative growth rate of black cutworm was lower on leaves from endophytic plants compared to control plants. Few other studies have examined the defense response of plants to colonization by Metarhizium spp. Endophytic colonization of maize plants by M. robertsii promoted plant growth and altered defense gene expression in maize, and suppressed growth rate of black cutworm larvae.

中文翻译：

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内生绿僵菌促进玉米生长、抑制昆虫生长并改变植物防御基因表达

摘要 绿僵菌属（Hypocreales：Clavicipitaceae）是一种昆虫病原体，可以作为内生菌建立并通过促进生长和抑制害虫来使寄主植物受益。本研究侧重于温室和实验室实验中绿僵菌-昆虫-植物的相互作用。我们用罗伯氏绿僵菌的孢子接种玉米 (Zea mays L.) 的种子，并评估 V4 玉米的叶和根内生定植，测量植物高度、叶绿素含量和地上生物量，以及黑地老虎 Agrotis ipsilon 的相对生长率（赫夫纳格尔）。此外，我们研究了选定的植物防御基因的表达。我们从接种种子的 91% 的植物中回收了 M. robertsii。与叶相比，我们在根中更频繁地检测到 M. robertsii。与对照植物相比，定植植物的植物高度和地上生物量更高。来自定植植物的叶组织显示出与植物防御有关的基因表达的变化。在饲养生物测定中，与对照植物相比，内生植物叶片上黑地老虎的相对生长速率较低。很少有其他研究检查了植物对绿僵菌定殖的防御反应。M. robertsii 对玉米植物的内生定植促进了植物生长并改变了玉米中的防御基因表达，并抑制了黑色地老虎幼虫的生长速度。与对照植物相比，内生植物叶片上黑地老虎的相对生长速度较低。很少有其他研究检查了植物对绿僵菌定殖的防御反应。M. robertsii 对玉米植物的内生定植促进了植物生长并改变了玉米中的防御基因表达，并抑制了黑色地老虎幼虫的生长速度。与对照植物相比，内生植物叶片上黑地老虎的相对生长速度较低。很少有其他研究检查了植物对绿僵菌定殖的防御反应。M. robertsii 对玉米植物的内生定植促进了植物生长并改变了玉米中的防御基因表达，并抑制了黑色地老虎幼虫的生长速度。