AUTHOR=Wang Long , Wang Xiaohui , Gao Fanqi , Lv Changning , Li Likun , Han Tong , Chen Fajun 

TITLE=AMF Inoculation Can Enhance Yield of Transgenic Bt Maize and Its Control Efficiency Against Mythimna separata Especially Under Elevated CO2

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.655060

DOI=10.3389/fpls.2021.655060

ISSN=1664-462X

ABSTRACT=<p>The promotion and application of transgenic <italic>Bt</italic> 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 <italic>Bt</italic> crops will face a new risk due to a decrease in exogenous toxin content under elevated carbon dioxide (CO<sub>2</sub>) concentration, thus negatively affecting the ecological sustainability of <italic>Bt</italic> 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 <italic>Bt</italic> crops under increasing CO<sub>2</sub> due to global climate change. In this study, the <italic>Bt</italic> maize and its parental line of non-transgenic <italic>Bt</italic> maize were selected and inoculated with a species of AMF (<italic>Funneliformis caledonium</italic>, synonyms: <italic>Glomus caledonium</italic>), in order to study the secondary defensive chemicals and yield of maize, and to explore the effects of <italic>F. caledonium</italic> inoculation on the growth, development, and reproduction of the pest <italic>Mythimna separata</italic> fed on <italic>Bt</italic> maize and non-<italic>Bt</italic> maize under ambient carbon dioxide concentration (<italic>a</italic>CO<sub>2</sub>) and elevated carbon dioxide concentration (<italic>e</italic>CO<sub>2</sub>). The results showed that <italic>e</italic>CO<sub>2</sub> 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 <italic>Bt</italic> gene expression in <italic>Bt</italic> maize leaves. <italic>F. caledonium</italic> inoculation increased maize yield, foliar JA, SA contents, <italic>Bt</italic> toxin contents, and <italic>Bt</italic> gene expression in <italic>Bt</italic> maize leaves, and positively improved the growth, development, reproduction, and food utilization of the <italic>M. separata</italic> fed on non-<italic>Bt</italic> maize. However, <italic>F. caledonium</italic> inoculation was unfavorable for the fitness of <italic>M. separata</italic> fed on <italic>Bt</italic> maize, and the effect was intensified when combined with <italic>e</italic>CO<sub>2</sub>. It is indicated that <italic>F. caledonium</italic> inoculation had adverse effects on the production of non-<italic>Bt</italic> maize due to the high potential risk of population occurrence of <italic>M. separata</italic>, while it was just the opposite for <italic>Bt</italic> 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 <italic>Bt</italic> maize under <italic>e</italic>CO<sub>2</sub>, and finally can enhance the insect resistance capacity of <italic>Bt</italic> crops, which will help ensure the sustainable utilization and safety of <italic>Bt</italic> crops under climate change.</p>