| Elevated CO2 concentration is one of characetristics of climate change, having not only direct influence on plant morphology, physiology and biochemistry, but also indirect effects on herbivorous insects that feed on the plants. The brown rice planthopper, Nilaparvata lugens, is one of the main migratory pests on the rice. Among numerous studies made on its biology, ecology and control, less focus has been on the effects of climate change. This thesis reports laboratory experiments to address questions:1) Do elevated CO2 affect feeding behaviors and life history traits of pesticide-resistant N. lugens? 2) Do elevated CO2 influence life history traits of N. lugens feeding on insect-resistant rice plants?1. Effects of elevated CO2 on fitness costs of imidacloprid-resistant N. lugens.Laboratory experiments were carried out to examine development, reproduction and survival of N. lugen strains differred in resistance to the pesticide imidacloprid by about 147 times, under the ambient (390μL·L-1) and elevated (780μL·L-1) CO2 treatments. The results showed a significant CO2× strain interaction for nymph and egg development time. For the susceptible strain, elevated CO2 extended nymph developmental duration, reduced the nymph survival rate and shortened egg duration. For the imidacloprid resistance strain, elevated CO2 shortened nymph developmental duration, increased the nymph survival rate and extended egg duration. For both strains, elevated CO2 reduced adult longevity, fertility and egg hatchability, delaying oviposition peak time and constrained the peak duration, as compared to the ambient CO2 treatment. The results indicate that elevated CO2 may be disadvantaged for the imidacloprid resistance N. lugens.2. Effects of elevated CO2 on feeding behaviors of pesticide-resistant N. lugens.Feeding behaviors of N. lugen differed by 147 times in imidacloprid resistance and by ca.480 times in buprofezin resistance were compared using electronic penetration graph (EPG) technique, under the ambient (390μL·L-1) and elevated (780μL·L-1) CO2 treatments. For imidacloprid resistance and susceptible strains, elevated CO2 decreased intracellular activity and phloem sap ingestion duration, extended activity in the xylem region, increased frequency of salivation, stylet movement, and activity in the xylem region, decreased frequency of intracellular activity in phloem region. There was a significant CO2× imidacloprid resistance interaction. Elevated CO2 reduced frequency of phloem sap ingestion of the susceptible strain, but increased frequency of phloem sap ingestion and activity in the xylem region of imidacloprid resistance strain. N. lugens exhibited a tendency to shorten the phloem sap ingestion duration under elevated CO2, and the buprofezin-resistant N. lugens decreased frequency of the penetration initiation under the elevated CO2 concentration (780μL·L-1) as opposed to the ambient CO2 (390μL·L-1). Under the two CO2 treatments, in comparison with the buprofezin susceptible planthoppers, the buprofezin-resistant spent less time for the salvation plus penetration movement and for the stylet activity in xylem region, increased the time and frequency of the intracellular activity in phloem region, but decreased the frequency of the phloem sap ingestion and the stylet activity in xylem region. According to these results, we predict that elevated CO2 may cause harmful effects on feeding behaviour of imidacloprid-resistant N. lugens, but may increase virulence of buprofezin-resistant N. lugens to rice.3. Effects of elevated CO2 on protective enzyme activity in pesticide-resistant N. lugens.Laboratory experiments were carried out to examine protective enzyme activity under 390μL·L-1 and 780μL·L-1 CO2 treatments in two pesticides resistant N. lugens. The results showed a significant CO2 × strain interaction for the response of enzymes. In imidacloprid-resistant N. lugens, elevated CO2 decreased total protein concentration and POD activities, increased SOD and CAT dynamics. In buprofezin-resistant N. lugens, elevated CO2 decreased total protein concentrations, increased POD and CAT activities. Meanwhile, in imidacloprid- and buprofezin-susceptible N. lugens, elevated CO2 increased total protein concentration but decreased SOD, POD and CAT activities. Under the two CO2 treaments, the SOD activity of buprofezin-resistant N. lugens was decreased compared to susceptible counterparts. The results suggest that elevated CO2 may cause harmful effects on pesticide-resistant N. lugens.4. Effects of elevated CO2 on life history traits of N. lugens feeding insect resistant rice.Experiments were carried out to examine effects of rice resistance to insects on development, reproduction and survival in Nilaparvata lugens. Planthopper-resistant (’IR36’) and -susceptible (’TN1’) rice cultivars were grown under 390μL·L-1 and 780μL·L-1 CO2 treatments, and fed to planthoppers. The results showed a significant CO2 × strain interaction for female fecundity. Fecundity decreased in’TN1’, while changed not clearly in’IR36’. For the two strains, elevated CO2 decreased nymph survival rate and female longevity, shortened the male nymph and egg duration. Under the both different CO2, the nymph and egg duration of’IR36’were longer than’TN1’, female longevity and spawning were less than’TN1’. The results suggested that elevated CO2 may decrease the resistant performances of the pest-resistant rice cultivar. |
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