Effects of elevated CO₂ and transgenic Bt cotton on plant chemistry, performance, and feeding of an insect herbivore, the cotton bollworm

Abstract

Effects of elevated atmospheric CO 2 (double-ambient CO 2 ) on the growth and metabolism of cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), fed on transgenic Bacillus thuringiensis (Berliner) (Bt) cotton [Cry1A(c)], grown in open-top chambers, were studied. Two levels of CO 2 (ambient and double-ambient) and two cotton cultivars (non-transgenic Simian-3 and transgenic GK-12) were deployed in a completely randomized design with four treatment combinations, and the cotton bollworm was reared on each treatment simultaneously. Plants of both cotton cultivars had lower nitrogen and higher total non-structural carbohydrates (TNC), TNC:Nitrogen ratio, condensed tannin, and gossypol under elevated CO 2 . Elevated CO 2 further resulted in a significant decrease in Bt toxin level in GK-12. The changes in chemical components in the host plants due to increased CO 2 significantly affected the growth parameters of H. armigera. Both transgenic Bt cotton and elevated CO 2 resulted in a reduced body mass, lower fecundity, decreased relative growth rate (RGR), and decreased mean relative growth rate in the bollworms. Larval life-span was significantly longer for H. armigera fed transgenic Bt cotton. Significantly reduced larval, pupal, and adult moth weights were observed in the bollworms fed elevated CO 2 -grown transgenic Bt cotton compared with those of bollworms reared on non-transgenic cotton, regardless of the CO 2 level. The efficiency of conversion of ingested food and of digested food of the bollworm were significantly reduced when fed transgenic Bt cotton, but there was no significant CO 2 or CO 2 × cotton cultivar interaction. Approximate digestibility of larvae reared on transgenic cotton grown in elevated CO 2 was higher compared to that of larvae fed non-transgenic cotton grown at ambient CO 2 . The damage inflicted by cotton bollworm on cotton, regardless of the presence or absence of insecticidal genes, is predicted to be more serious under elevated CO 2 conditions because of individual compensatory feeding on host plants caused by nitrogen deficiency.

Constitutive and herbivore-inducible glucosinolate concentrations in oilseed rape (Brassica napus) leaves are not affected by Bt Cry1Ac insertion but change under elevated atmospheric CO2 and O3

“…Previously, Bt cotton and a corresponding non-transgenic line were shown to exhibit similar responses to elevated CO 2 , as total non-structural carbohydrates were increased and total nitrogen was decreased in plants of both types, which is evidence of equivalence in the way these lines respond to elevated CO 2 (Chen et al 2005). Total phenolics were lower in Bt cotton compared with the non-transgenic parent line under low nitrogen availability, but again both lines showed similar total phenolic, terpenoid aldehyde, condensed tannin, and carbonnitrogen responses to elevated CO 2 (Coviella et al 2002).…”

“…Elevated CO 2 typically increases plant biomass and net photosynthesis (Poorter et al 1997), whereas O 3 is a stress factor that decreases photosynthesis rates, and leads to the formation of reactive oxygen species in the plant leaf apoplast (Fiscus et al 2005;Kangasjärvi et al 2005). The eVects of future climate change on the metabolism and plant-herbivore interactions of GM crop cultivars are still largely unexplored, but indications for altered Bt toxin concentrations in response to elevated CO 2 have been detected on Bt cotton (Coviella et al 2000(Coviella et al , 2002Chen et al 2005).…”

Performances of an expanding insect under elevated CO2 and snow cover in the Alps

“…The studies carried out under similar situations have shown contrasting responses on larval performance. Several highlighted a negative response (Hättenschwiler & Schafellner 1999, Chen et al 2005, whereas others showed no variations (Goverde et al 2002, Williams et al 2003 or a positive effect (Goverde et al 1999). Asshoff & Hät tenschwiler (2006), in an experiment carried out in the same FACE site, showed that al teration in needle chemistry had a reduced effect on larch bud moth performance.…”

Transgenic Bacillus thuringiensis (Bt) cotton (Gossypium hirsutum) allomone response to cotton aphid, Aphis gossypii, in a closed-dynamics CO2 chamber (CDCC)

“…Coviella et al (2002) and Chen et al (2005b) reported that elevated CO 2 results in significant increases in carbonbased secondary compounds (e.g., starch, condensed tannins, gossypol) and decreases in nitrogen-based compounds (e.g., Bt toxin protein) in transgenic Bacillus thuringiensis Gossypium hirsutum (Bt cotton), as predicted by the CNB hypothesis. Lindroth et al (1995) reported that condensed tannin concentrations in paper birch (Betula papyrifera) doubled when trees were grown in elevated CO 2 , while Fajer et al (1991) reported that neither iridoid glycoside nor fiber concentrations in Plantago lanceolata were affected by CO 2 levels.…”

“…Foliar Bt toxin of GK-12 was measured using enzymelinked immunosorbent assay (ELISA) test (Chen et al 2005b). Leaf samples were dried at 38°C for 72 h, and ground with liquid nitrogen and quartz sand using a mortar and pestle to measured condensed tannin content by the method of Chen et al (2005b), and gossypol content by the method of Xu and Zhang (2005).…”