Effect of elevated CO2 on interactions between the host plant Phaseolus vulgaris and the invasive western flower thrips, Frankliniella occidentalis

Elevated CO2 can alter the growth and development of herbivorous insects by changing the host plants, including nutrient quality and defensive chemicals/metabolites. The western flower thrips, Frankliniella occidentalis, is a highly destructive invasive pest in agriculture worldwide. In this study, we investigated the effect of elevated CO2 on the growth, development and reproduction of F. occidentalis by changing its host plant of kidney bean Phaseolus vulgaris and, in particular, the hormonal regulation of the transcription factors in F. occidentalis. Elevated CO2 increased the contents of total amino acids, soluble sugar and soluble protein in P. vulgaris. Besides, elevated CO2 shortened the pre-adult duration (PAD) and longevity of F. occidentalis, lowered their survival rate and increased the weight and fecundity. PAD was positively correlated with the expression levels of br, Krh-1, JHEH and EIP in F. occidentalis larvae. The longevity of F. occidentalis female adults was negatively correlated with JHEH, but positively correlated with ER and EIP. The fecundity of F. occidentalis female adults was negatively correlated with ER and Vg, but positively correlated with JHEH. We have demonstrated that elevated CO2 could enhance the nutrient quality of host plants and, therefore, accelerate the development and reproduction of F. occidentalis, which is regulated by JH, MH and Vg.