Simultaneous Increase in CO2 and Temperature Alters Wheat Growth and Aphid Performance Differently Depending on Virus Infection

Abstract

Climate change impacts crop production, pest and disease pressure, yield stability, and, therefore, food security. In order to understand how climate and atmospheric change factors affect trophic interactions in agriculture, we evaluated the combined effect of elevated carbon dioxide (CO2) and temperature on the interactions among wheat (Triticum aestivum L.), Barley yellow dwarf virus species PAV (BYDV-PAV) and its vector, the bird cherry-oat aphid (Rhopalosiphum padi L.). Plant traits and aphid biological parameters were examined under two climate and atmospheric scenarios, current (ambient CO2 and temperature = 400 ppm and 20 °C), and future predicted (elevated CO2 and temperature = 800 ppm and 22 °C), on non-infected and BYDV-PAV-infected plants. Our results show that combined elevated CO2 and temperature increased plant growth, biomass, and carbon to nitrogen (C:N) ratio, which in turn significantly decreased aphid fecundity and development time. However, virus infection reduced chlorophyll content, biomass, wheat growth and C:N ratio, significantly increased R. padi fecundity and development time. Regardless of virus infection, aphid growth rates remained unchanged under simulated future conditions. Therefore, as R. padi is currently a principal pest in temperate cereal crops worldwide, mainly due to its role as a plant virus vector, it will likely continue to have significant economic importance. Furthermore, an earlier and more distinct virus symptomatology was highlighted under the future predicted scenario, with consequences on virus transmission, disease epidemiology and, thus, wheat yield and quality. These research findings emphasize the complexity of plant–vector–virus interactions expected under future climate and their implications for plant disease and pest incidence in food crops.

Elevated Carbon Dioxide and Nitrogen Impact Wheat and Its Aphid Pest

“…In our study, eCO 2 significantly increased tiller number and aboveground dry biomass, which is consistent with previous findings (Bloom et al, 2010;Taub, 2010;Trębicki et al, 2016;Walker et al, 2017;Moreno-Delafuente et al, 2020). The observed eCO 2 -induced reduction in leaf chlorophyll content (a proxy for plant N content) has also been noted by others (Myers et al, 2014;Ryan et al, 2014;Dáder et al, 2016;Trębicki et al, 2016; Vassiliadis et al, 2018;Moreno-Delafuente et al, 2020). The mechanisms responsible for such a reduction are not fully understood, though Myers et al (2014) proposed that it may be due to a combination of factors including carbohydrate dilution, slower N uptake in the roots and decreased transpiration-driven N flow, among others.…”

“…This supports that different insectplant models respond differently to eCO 2 (Ryalls and Harrington, 2016). Several studies have reported an increase in aphid fecundity (Jiang et al, 2018) and abundance (Ryan et al, 2015), while others a decrease in aphid fecundity under eCO 2 (Newman et al, 1999;Awmack et al, 2004;Oehme et al, 2013;Ryan et al, 2014;Dáder et al, 2016;Trębicki et al, 2016;Moreno-Delafuente et al, 2020). Although we found that eCO 2 significantly decreased the fecundity of the bird cherry-oat aphid, it was overall lower than that reported by Trębicki et al (2016) on the same insectplant model and under similar conditions (controlled plant growth chambers set at 20°C; aCO 2 = 385 ppm and eCO 2 = 650 ppm).…”

“…over a period of time equivalent to the pre-reproductive period (M d ), and the mean number of nymphs produced per aphid female over a 10-day period (M 10 ). Additionally, we calculated the mean generation time (T d = d/0.738), the intrinsic rate of natural increase [r m = 0.738 (ln M d )/d], and the mean relative growth rate (RGR = r m /0.86) following calculations described by Wyatt and White (1977) and commonly used to assess aphid performance (Dáder et al, 2016;Trębicki et al, 2016;Moreno-Delafuente et al, 2020).…”

“…Climate change will impact aphid population size, migration activity, and distribution (Luck et al, 2011;Ryalls and Harrington, 2016;Trębicki et al, 2017;Deutsch et al, 2018;Trębicki and Finlay, 2019;Trębicki, 2020). In particular, eCO 2 has shown to increase aphid metabolic rates and, thus, feeding behavior (Robinson et al, 2012;Trębicki et al, 2016), and to alter aphid development and fecundity through changes in host biochemistry (Johnson and Jones, 2017;Johnson and Züst, 2018;Trębicki and Finlay, 2019;Moreno-Delafuente et al, 2020). There are contrasting findings in terms of the effect of eCO 2 on aphid fecundity (Xing et al, 2003;Robinson et al, 2012;Oehme et al, 2013;Ryan et al, 2014;Ryalls and Harrington, 2016;Trębicki et al, 2016;Moreno-Delafuente et al, 2020), as it can be highly species/host specific (Hughes and Bazzaz, 2001).…”

“…In particular, eCO 2 has shown to increase aphid metabolic rates and, thus, feeding behavior (Robinson et al, 2012;Trębicki et al, 2016), and to alter aphid development and fecundity through changes in host biochemistry (Johnson and Jones, 2017;Johnson and Züst, 2018;Trębicki and Finlay, 2019;Moreno-Delafuente et al, 2020). There are contrasting findings in terms of the effect of eCO 2 on aphid fecundity (Xing et al, 2003;Robinson et al, 2012;Oehme et al, 2013;Ryan et al, 2014;Ryalls and Harrington, 2016;Trębicki et al, 2016;Moreno-Delafuente et al, 2020), as it can be highly species/host specific (Hughes and Bazzaz, 2001). In terms of aphid development time, the findings can vary; for example, eCO 2 did not affect the development time of R. padi reared on wheat (Trębicki et al, 2016) but significantly increased that of Myzus persicae reared on bell pepper (Dáder et al, 2016).…”