Volatiles Released From Rice Plants Infected By The Rice Brown Planthopper Nilaparvata Lugens: Primary Characteristics And Effects Of Some Biotic Factors On Its Activity

Based on previous research results, primary characteristics of herbivore-induced rice volatiles and effects of some biotic factors on its activity were studied in a model system involving rice, the rice brown planthopper, Nilaparvata lugens (Stal), and its egg parasitoid, Anagrus nilaparvatae Pang et Wang. The results are summarized as follows:1) There were significant differences in attractiveness to the parasitoid of rice volatiles released from various varieties and developmental stages. Attractiveness of the volatiles from undamaged rice plant of TNI to the parasitoid was significantly stronger than that of Nabeshi, while no difference was found between other varieties. After rice plants were infected by N. lugens, volatiles from TNI plants showed significantly stronger attractiveness to the parasitoid than those from Nabeshi, IR26, Bing 9759 but weaker than that from Shanyou 63. More parasitoids oriented to volatiles from 60-day-old rice plants infected by N. lugens compared to those from 30-day-old and 90-day-old rice plants.2) Nilaparvata lugens density and continuously feeding time obviously influenced the activity of volatiles emitted from rice plants attractive to the parasitoid. Volatiles released from rice plants, infected with 1, 5, 40 or 80 female N. lugens adults per plant for 1 day, did not show any attractiveness to the parasitoid compared to those from undamaged plants, while strong activities were found in volatiles from rice plants infected with 10 or 20 female N. lugens adults per plant for 1 day. With the increase of feeding time of N. lugens on rice plants, the number of the parasitoid attracted by the volatiles from rice plants changed from low to high to low. Unlike volatiles from rice plants continuously fed by N. lugens for 1 h, 2 h, 48 h or 72 h, which did not attract more parasitoids compared to the controls, volatiles emitted from rice plants infected with N. lugens for 6 h, 12 h or 24 h showed significantly stronger attractiveness to the parasitoid than the controls..3) Nilaparvata lugens induced rice plants to release volatiles systemically and thischaracteristic did not obviously changed with different leaf node infection by N. lugens. Undamaged rice plants could perceive the volatile signals released from aerial part of neighboring N. lugens-infected rice plants but not cues secreted by neighboring plant roots and released volatiles to attract the parasitoid. This suggests that rice plants could communicate each other via volatiles that they released.4) In comparison to volatiles released by undamaged rice plants, volatiles from rice plants infected by N. lugens showed obvious diurnal-cycle with maximum emission from 12:00 to 16:00 and minimum emission from 22:00 to 4:00. Moreover, N. lugens-infected plants released higher amount of volatiles than undamaged plants at daytime but not at night.