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Elevated CO2 levels influence metabolism and development in Helicoverpa armigera on chickpea
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Elevated CO2 levels influence metabolism and development in Helicoverpa armigera on chickpea

  1. Cotton bollworm, Helicoverpa armigera is one of the most important constraints to crop production in Asia, Africa, Australia, and the Mediterranean Europe (Sharma 2005). Atmospheric concentration of CO2 has increased from 280 ppm during the pre-industrial period to 396 ppm in 2013 (Mauna Loa Observatory: NOAA-ESRL), and is anticipated to double by the end of the 21st century (IPCC 2007). Elevated CO2 levels may influence insect damage and the survival and development insect herbivores (Wu et al. 2006). Therefore, the present studies were undertaken on the influence of CO2 on metabolic processes, which influence the survival and development of H. armigera. Results and Discussion Elevated CO2 differentially influences H. armigera larval survival and development Larval survival was greater under elevated CO2 as compared to the larvae fed on plants grown at ambient CO2 (350 ppm) (Fig. 1). Fig. 1. Survival and development of H. armigera larvae fed on chickpea plants grown at different levels of CO2. Fig. 5. Effect of CO2 on aminopeptidase, a Bt toxin receptor, in the midgut of H. armigera larvae fed on chickpea plants grown at different levels of CO2 in the OTCs. Fig. 3. Effect of CO2 on activity of proteases in H. armigera larvae fed on chickpea grown at different levels of CO2 in the OTCs. *For more information, please write to: Dr HC Sharma, Principal Scientist – Entomology, ICRISAT. Email: h.sharma@cgiar.org Materials and methods Chickpea plants: Different CO2 levels (350, 550, and 750 ppm) were maintained in three open top chambers (OTCs) using generators connected to CO2 cylinders. Fifteen-day old chickpea plants of ICCL 86111 (R) and JG 11 (S), were transferred to OTCs from greenhouse. There were three replications in each OTC, 10 pots in each replication, and 5 plants in each pot. Larval infestation: Neonates of H. amrigera larvae were reared on the chickpea plants at the flowering stage, and allowed to feed till they attained late fourth-instar. The larvae were collected 15 days after infestation and subjected to biochemical analysis. Enzyme assays: The midgut of H. armigera larvae were collected by dissecting them, and homogenized in glycine-NaOH buffer, 0.1 M, pH 7.0 at 4 oC. Activity of proteases (Parde et al. 2010) and amylase (Kotkar et al. 2009) was measured spectrophotometrically. Cytochrome c oxidase was measured in isolated mitochondria from the H. armigera larvae body membranes (Akbar et al. 2012). Fig. 4. Effect of CO2 on cytochrome c oxidase from mitochondria of H. armigera fed on chickpea plants grown at different levels of CO2 in the OTCs. Effect of elevated CO2 on activity of amylase, proteases and cytochrome c oxidase in H. armigera • Amylase activity increased in H. armigera larvae with an increase in CO2 levels in both the genotypes of chickpea (Fig. 2), while trypsin, chymotrypsin, elastase and total protease activities decreased in larvae fed on ICPL 86111, but increased in JG11 (Fig. 3). • Activity of cytochrome c oxidase in H. armigera larvae increased with an increase in CO2 levels, indicating increased consumption of oxygen by the mitochondria under high concentrations of CO2 (Fig. 4). • Aminopeptidase is the receptor for Bt toxins in the brush border membrane of midgut epithelium in insect pests. Aminopeptidase activity in H. armigera larvae decreased with an increase in CO2 (Fig. 5), which might reduce the effectiveness of Bt-transgenic crops. Conclusions Elevated CO2 will influence the survival and development of H. armigera larvae by directly affecting their metabolism through altering activities of proteases, carbohydrases and of mitochondrial enzymes, and also indirectly by altering plants chemistry, which in turn may influence consumption and utilization of food. References Akbar SMD, Sharma HC, Jayalakshmi SK and Sreeramulu K. 2012. Interaction of plant cell signaling molecules, salicylic acid and jasmonic acid, with the mitochondria of Helicoverpa armigera, Journal of Bioenergetics and Biomembranes, 44: 233–241. Sharma HC. 2005. Heliothis/Helicoverpa management: Emerging trends and Strategies for Future Research. New Delhi, India: Oxford and IBBH Publishing Co. 469 pp. Wu G, Chen FJ and Ge F. 2006. Response of multiple generations of cotton bollworm Helicoverpa armigera Hübner, feeding on spring wheat, to elevated CO2. Journal of Applied Entomology 130: 2-9. Kotkar HM, Sarate PJ, Tamhane VA, Gupta VS and Giri AP. 2009. Responses of midgut amylases of Helicoverpa armigera to feeding on various host plants. Journal of Insect Physiology 55: 663–670. Parde VD, Sharma HC and Kachole MS. 2010. In vivo inhibition of Helicoverpa armigera gut pro-proteinase activation by non-host plant protease inhibitors. Journal of Insect Physiology 56: 1315–1324. Fig. 2. Amylase activity in midgut of H. armigera larvae fed on chickpea plants grown at different levels of CO2. H. armigera on chickpea Open top chambers (OTCs) Elevated CO2 Levels Influence Metabolism and Development in Helicoverpa armigera on Chickpea S MD Akbar, AR War, RS Munghate, M Pathania, SP Sharma and HC Sharma* International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324, Telangana, India Jul 2014ICRISAT is a member of the CGIAR Consortium
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