Selectivity And Mechanism Of Q-biotype Whitefly, Bemisia Tabaci For Different Varieties Of Tobacco, Nicotiana Tabacum

Bemisia tabaci (Gennadias) is an important worldwide insect pest on economic crops. For its short life history, high fecundity and easy acquisition of pesticide-resistance ability, selecting pest-resistant plant strains turns out to be one of the efficient ways to control B. tabaci. We conducted a series of studies on the selection mechanisms for different tobacco varieties with whitefly in this thesis, with the objective of providing a theoretical foundation for screening insect-resistant tobacco varieties and management of this pest. Our main results and conclusions are as follows:1. Identification of biotype of B. tabaci:Using mitochondrial cytochrome oxidase I (mt COI) gene sequences for identificated biotypes of B. tabaci on the pepper crops in the greenhouses in Anhui. The result indicated that the COI gene fragment (866bp) of this population and Q-biotype B. tabaci of China with accession number were EU255280.1, EU376984.1 had more than 99% homology. Therefore, the biotype of this experimental population whitefly is Q-biotype.2. Selectivity test:Tests to determine the relative host plant preferences of Q-biotype B. tabaci on eight different tobacco varieties were performed under control conditions with 22～26℃, RH 60%～80%,14L:10D. The result indicated that different feeding and egg-laying to different tobacco varieties.’CF225’,’CF226’, ’CF220’are more favorite varieties for B. tabaci. The quantity of adults and their eggs on’K326 (C8)’and ’Yinyan117’, however, were lower.3. Population dynamics analysis of B. tabaci in greenhouse:Observed spatio-temporal dynamics of B. tabaci on eight different tobacco varieties in greenhouse. Our results showed that the population density varied with different strains, height and time, and there were significant differences among them. The density of populations hosted on’CF226’,’CF225’,’CF220’were higher, and it turned out to be lower on’K326(E3)’,’K326(C8)’,’Yunyan117’. The result and selectivity test were consistent.4. Developmental of B. tabaci on different tobacco varieties:Investigated the development period and the fecundity of B. tabaci on different tobacco varieties in the incubator with 26 ± 0.5 ℃, RH 60%～80%, and then constructed the life table of the whitefly. Our results showed that the B. tabaci had high fecundity and lived well on any tobacco varieties. However, it developed slower on ’CF225’ and ’CF226’, but faster on’K326 (C8)’and’Yunyan117’,and it had lower fecundity on’K326 (C8)’, ’Yunyan117’.5. The mechanism for selectivity of Q biotype B. tabaci on different tobacco varieties:Investigated the trichome density, the color of leaves and the behavior reaction to different tobacco varieties. The result indicated that the trichome density was significantly different on different tobacco varieties and has significantly correlated with adult host preference and the number of eggs laid. The B. tabaci showed a strong behavioral tendency to the high number of trichome density leaves and kelly leaves, but there were no different reactions of B. tabaci to different tobacco varieties.