AMF Inoculation Can Enhance Yield of Transgenic Maize and Its Control Efficiency Against Especially Under Elevated CO

The promotion and application of transgenic crops provides an approach for the prevention and control of target lepidopteran pests and effectively relieves the environmental pressure caused by the massive usage of chemical pesticides in fields. However, studies have shown that crops will face a new risk due to a decrease in exogenous toxin content under elevated carbon dioxide (CO) concentration, thus negatively affecting the ecological sustainability of crops. Arbuscular mycorrhizal fungi (AMF) are important beneficial microorganisms that can effectively improve the nutrient status of host plants and are expected to relieve the ecological risk of crops under increasing CO due to global climate change. In this study, the maize and its parental line of non-transgenic maize were selected and inoculated with a species of AMF (, synonyms: ), in order to study the secondary defensive chemicals and yield of maize, and to explore the effects of inoculation on the growth, development, and reproduction of the pest fed on maize and non- maize under ambient carbon dioxide concentration (CO) and elevated carbon dioxide concentration (CO). The results showed that CO increased the AM fungal colonization, maize yield, and foliar contents of jasmonic acid (JA) and salicylic acid (SA), but decreased foliar Bt toxin content and gene expression in maize leaves. inoculation increased maize yield, foliar JA, SA contents, toxin contents, and gene expression in maize leaves, and positively improved the growth, development, reproduction, and food utilization of the fed on non- maize. However, inoculation was unfavorable for the fitness of fed on maize, and the effect was intensified when combined with CO. It is indicated that inoculation had adverse effects on the production of non- maize due to the high potential risk of population occurrence of , while it was just the opposite for maize. Therefore, this study confirms that the AMF can increase the yield and promote the expression levels of its endogenous (JA, SA) and exogenous (Bt toxin) secondary defense substances of maize under CO, and finally can enhance the insect resistance capacity of crops, which will help ensure the sustainable utilization and safety of crops under climate change.