Elevated CO2 alters the feeding behaviour of the pea aphid by modifying the physical and chemical resistance of Medicago truncatula |
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Authors: | HUIJUAN GUO YUCHENG SUN YUEFEI LI XIANGHUI LIU PINGYAN WANG KEYAN ZHU‐SALZMAN FENG GE |
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Institution: | 1. State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, , Beijing, 100101 China;2. Graduate University of Chinese Academy of Sciences, , Beijing, 100049 China;3. Department of Entomology, Texas A&M University, , College Station, TX, 77843 USA |
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Abstract: | Elevated CO2 compromises the resistance of leguminous plants against chewing insects, but little is known about whether elevated CO2 modifies the resistance against phloem‐sucking insects or whether it has contrasting effects on the resistance of legumes that differ in biological nitrogen fixation. We tested the hypothesis that the physical and chemical resistance against aphids would be increased in Jemalong (a wild type of Medicago truncatula) but would be decreased in dnf1 (a mutant without biological nitrogen fixation) by elevated CO2. The non‐glandular and glandular trichome density of Jemalong plants increased under elevated CO2, resulting in prolonged aphid probing. In contrast, dnf1 plants tended to decrease foliar trichome density under elevated CO2, resulting in less surface and epidermal resistance to aphids. Elevated CO2 enhanced the ineffective salicylic acid‐dependent defence pathway but decreased the effective jasmonic acid/ethylene‐dependent defence pathway in aphid‐infested Jemalong plants. Therefore, aphid probing time decreased and the duration of phloem sap ingestion increased on Jemalong under elevated CO2, which, in turn, increased aphid growth rate. Overall, our results suggest that elevated CO2 decreases the chemical resistance of wild‐type M. truncatula against aphids, and that the host's biological nitrogen fixation ability is central to this effect. |
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Keywords: | Acyrthosiphon pisum legume plant nitrogen fixation resistance trichome |
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