Medicago Truncatula Responses To Pea Aphids Acyrthosiphon Pisum Under Elevated CO₂

The concentrations of atmospheric carbon dioxide (CO2) continue to grow arouses the scientists’ enormous interest. Increasing concentrations of atmospheric CO2 are considered to affect plants, animals and the entire ecosystems. Elevated CO2 has a cascading effect on plant and in turn affect the herbivorous insects. The performance of herbivore insects is determined directly by the quality of host plants. Elevated CO2 induced a decline in foliar nitrogen, which reduced the growth of chewing insects. Phloem-sucking insects (i.e.aphid), however, had species-specific responses to elevated CO2 and were the only feeding guild to respond positively to elevated CO2. Although many studies attempt to illuminate the interaction between aphids and plants under elevated CO2, few studies can explain why some aphids are more successful than other chewing insects in elevated CO2. In this study, we used open-top chambers (OTC) to analyze the effects of elevated CO2 on the interaction between legume plants Medicago truncatula and pea aphids Acyrthosiphon pisum. We used M. truncatula A17, Jester and R108 to clarify the effects of host plant nutrition, resistance on aphid fitness under elevated CO2 level. These results provided the scientific evidence to integrated pest management in the future increasing concentrations of atmospheric CO2.Through the analysis of elevated CO2 concentration under the pea aphid population dynamics in three genotypes of M. truncatula, feeding behavior and Medicago truncatula nutritional status. The results showed that elevated CO2 concentration increase with increasing CO2 concentration in the A17 and R108 so the pea aphid population increased in the number, and Jester of the pea aphid population declined. The elevated CO2 concentration increased the resistance of pea aphids, and the susceptible genotype was more sensitive to the genotype, and the genotype was more resistant to it. The most sensitive genotypes of M. truncatula R108 so with elevated CO2 biomass also increased, and A17 nodule number changed, Jester in these two aspects had no obvious change. The increase of atmospheric CO2 concentration changed the resistance of three genotypes of M. truncatula of pea aphids.The pea aphid of Medicago truncatula after induced by salicylic acid on A17 accumulation of jasmonic acid was not affected. At the same time by the aphid infested after A17 of salicylic acid in the path of the BGL, PR, CHTN the expression level of somewhat increased in elevated CO2 concentration under the condition of, and Jester salicylic acid path only PR expression was increased, the other two expression did not change significantly. The expression of LOX in the way of Jester Jasmine acid decreased with the increase of CO2 concentration, but there was no significant change of A17. The average relative growth rate of the pea aphid on the A17 was increased by the increase of CO2, but the relative growth rate of the aphids on the Jester was not affected. CO2 concentration increase reduces the A17 plants on the pea aphid first arrived in El wave and the time required for first arrived in E2 wave time required, also increased the E2 wave duration, but Jester plants of these indexes for the pea aphid had not changed.