Feeding behavioral response of cotton aphid, Aphis gossypii, to elevated CO2: EPG test with leaf microstructure and leaf chemistry

Abstract

AbstractEffect of elevated CO2 on feeding behavior of the cotton aphid, Aphis gossypii (Glover) (Hemiptera: Aphididae), was investigated using electrical penetration graphs (EPG) on cotton, Gossypium hirsutum L. (Malvaceae). Leaf microstructures and foliar soluble constituents were also measured simultaneously to quantify the impact of foliar changes on leaf nutritional quantity and quality, owing to elevated CO2, on stylet penetration and food‐quality plasticity of A. gossypii. Significant increases in fresh body weight, fecundity, and population abundances of A. gossypii were found in elevated CO2 in contrast to ambient CO2. Elevated CO2 influenced the feeding behavior, as evidenced by altered EPG recordings, including the increased non‐penetration period (walking and finding the feeding site), E2<8 min (probes with sustained ingestion of <8 min), and first E2>8 min (first occurrence of probes with sustained ingestion of >8 min), and decreased E2>8 min recordings. Moreover, leaf microstructures were significantly affected by CO2 levels, with thinner upside epidermis (UPE) and thicker underside epidermis (UDE), sponge tissues (ST), and fence tissues under elevated CO2 compared to that in ambient CO2. Therefore, it is expected that A. gossypii spend more time penetrating the thicker leaf UDE and ST when the host plant is exposed to elevated CO2. Furthermore, elevated CO2 significantly enhanced foliar soluble matter, including soluble sugars (SS), free amino acids and fatty acids (FFA), and total soluble matter (TSM), which was congruent with significant increase or decrease in leaf turgor or osmotic potential. Increased leaf turgor and leaf soluble constituents favored ingestion in A. gossypii, resulting in increases in fresh body weight, fecundity, and population abundances under elevated CO2. These feeding behaviors and resulting population growth parameters are consistent with the significant positive correlations between aphid fresh body weight and foliar FFA/TSM, between A. gossypii fecundity and foliar SS of cotton plants, and between the time of E2<8 min recordings and leaf turgor.