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Effect of heat and drought stress in pigeonpea on the expression of resistance to helicoverpa armigera
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Effect of heat and drought stress in pigeonpea on the expression of resistance to helicoverpa armigera

  1. Effect of heat and drought stress in pigeonpea on the expression of resistance to Helicoverpa armigera HC Sharma, AR War, SP Sharma, SMD Akbar and M Pathania International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324, Telangana, India. Conclusions • Heat and drought stressed plants were more susceptible to damage by H. armigera. Flavonol content and NBI were greater in stressed plants, which corresponded to greater weight gain by H. armigera larvae. References Sharma HC, Pampapathy G, Dhillon MK and Ridsdill-Smith TJ. 2005. Detached leaf assay to screen for host plant resistance to Helicoverpa armigera. Journal of Economic Entomology 98: 568 - 576. Sharma HC. 2014. Climate change effects on insects: Implications for Crop Protection and Food Security. Journal of Crop Improvement 28: 229 - 259. For more information, please write to: Dr HC Sharma, Principal Scientist – Entomology, ICRISAT. Email: h.sharma@cgiar.org Effect of heat and water stress on expression of resistance to H. armigera • Five genotypes of pigeonpea were grown under greenhouse (27 + 5 ℃ and 65 - 95% RH) and heat and water stress conditions (37 ± 5℃ and 25 - 65% RH) during the summer season (April - May) (Plate 1). • Plants raised in the greenhouse were watered on alternate days, while those raised outside the greenhouse were exposed to heat and water stress. • After 20 days of germination, fully expanded trifoliates were tested for resistance to H. armigera using detached leaf assay (Plate 2) (Sharma et al., 2005). • Data were recorded on leaf damage, larval survival and larval weights. • Total chlorophyll and flavonol contents and nitrogen balance index (NBI) were estimated using polyphenol meter (Force A, Dualex Scientific DX11170, France). Results • ICPL 187-1 and ICPL 332 WR suffered maximum leaf damage (DR 7.67) in plants raised under heat and water stress. However, ICPL 87, ICPL 88039 and ICPL 98008 suffered more damage in plants grown under greenhouse conditions. • There were no differences in larval survival on plants raised under greenhouse and heat and water stress conditions. • Weights of H. armigera larvae (Fig. 1) were higher (1.20 mg/larvae) in plants grown under heat and water stress as compared to the larvae fed on plants grown under greenhouse conditions (0.52 mg/larva). • Flavonol content of pigeonpea genotypes grown under greenhouse conditions ranged from 0.89 - 1.07 μg cm-2 as compared to 0.72 - 1.17 μg cm-2 in plants grown under heat and water stress (Fig. 3). • NBI index of the plants grown under greenhouse ranged from 19.2 to 32.5 and of the plants raised under heat and water stress from 18.7 to 36.3. US S Plate 2. Detached leaf assay to evaluate pigeonpea genotypes for resistance to H. armigera (R - resistant and S - susceptible). July 2014ICRISAT is a member of the CGIAR Consortium Fig. 1. Larval weights of H. armigera on different pigeonpea genotypes grown under greenhouse and heat and water stressed conditions. Fig. 3. Flavonol content of pigeonpea genotypes grown under greenhouse and stressed conditions. • Chlorophyll content of plants grown under greenhouse ranged from 17.2 - 31.3 μg cm-2, whereas in stressed plants it varied from 21.4 - 41.5 μg cm-2 (Fig. 2), suggesting increased accumulation of chlorophyll under stressed conditions. Fig. 2. Chlorophyll content of pigeonpea genotypes grown under greenhouse and stressed conditions. Helicoverpa armigera resistant ICPL 332 WR (a) and susceptible ICPL 87 (b) genotypes of pigeonpea. Introduction • Global warming and climate change will trigger major changes in herbivore plant interactions and efficacy of crop protection technologies (Sharma, 2014). • Chemical composition of plants will change in direct response to global warming and climate change, affecting plant damage and growth and development of insect pests. • We studied the effect of heat and water stress on expression of resistance to pod borer, Helicoverpa armigera in pigeonpea. Plate 1. Pigeonpea plants grown under unstressed (US) and heat and water stressed (S) conditions during the summer season. R S a b
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