| In a simple food web involving rice, rice planthoppers, brown planthopper (BPH), Nilaparvata lugens (Stal), and whitebacked planthopper (WBPH), Sogatella furcifera (Horvath), and their natural enemies, an egg parasitoid, Anagrus nilaparvatae Pang et Wang and a predatory bug Cyrtorhinus lividipennis (Reuter), volatiles mediated intra- and interspecific interactions were studied based on the previous research. The results are as follows:1) Behavioral responses of the rice planthoppers to volatiles emitted from healthy rice plants and rice plants sucked by conspecific and heterospecific planthoppers were studied with H-shaped olfactometer. The results showed that rice planthoppers, BPH and WBPH oriented significantly towards the odours emitted from healthy rice plants compared with the plain air. Volatiles emitted from rice plants infected by one planthopper species slightly (100 female adults of planthoppers per 10 seedlings, infected for 12h) could attract the other species significantly, but had no significant effect on conspecific planthopper. With the increase of damage degrees (rice plants infected by planthoppers more than Id), both BPH and WBPH preferred volatiles emitted from intact rice plants over those from damaged rice plants. BPH and WBPH showed no preference between the volatiles from plants damaged by conspecific planthoppers and those by heterospecific rice planthoppers.2) Behavioral responses of the rice planthoppers to volatiles emitted from the complex of rice plants together with planthoppers (female adults or nymphs) and their natural enemies were conducted using H-shaped olfactometer. The results demonstrated that both BPH and WBPH showed no preference between the odours from the complexes of rice plants together with female adults of planthoppers and the parasitoid or the predator and those from rice plants with planthoppers. This suggested that the existence of the parasitoid and the predator did not influence the host searching behavior of both planthoppers via volatilesignals.3) More than 30 components were collected from headspace of rice plants infected by rice planthoppers with solid phase microextractrion (SPME), among which 16components were identified by GC-MS. These were 5 aliphatic saturated hydrocarbons, 5 aliphatic unsaturated hydrocarbons, 2 ketones, 2 terpenes, 1 aliphaatic aldehyde and 2-Pentyl-Furan. In those volatiles profiles, the proportions of hydrocarbons, ketones and 8 unknown components were relatively higher, while terpenes, aliphatic aldehyde and 2-Pentyl-Furan were very low, which were not more than 1%. There were significant differences in the total amount of volatiles among different treatments. Of those, the amout of volatiles from rice plants damaged by BPH for 4d was the highest. No significant difference in the amount of volatiles was found between undamaged and mechanically damaged rice plants. Significant difference in the amount of volatiles exited among rice plants with different damage levels by the conspecific rice planthopper. The total amount of volatiles changed from high to low to high with the increase of damage degree and the lowest treatments were rice plants sucked by BPH and WBPH for Id. Significant differences were also found in the proportions of volatiles components among different treatments, but there were no apparent difference between undamaged and mechanically damaged rice plants except U4. Five components in some damaged rice plants were higher than those in healthy rice plants, while eight were lower. The proportions of 2-Pentyl-Furan and Limonene in various treatments changed randomly. Composition ratios of volatiles were also different among rice plants with different damage degree by conspecific rice planthopper. 2-Pentyl-Furan and 2,2,6-trimethyl-Cyclohexanone from rice plants damaged by BPH and WBPH for 12h were the highest, but they decreased with the increase of damage degree. Significant differences in proportions were also found among rice plants with the same damage degree by different species of rice plant...
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