Distribution Status Of Bemisia Tabaci (Gennadius) Q-biotype In China And The Phylogenetic Analysis Based On MtCOI Sequences

The sweet potato whitefly, Bemisia tabaci (Gennadius), is a serious pest of different agricultural crops all over the world. B. tabaci was considered a species complex containing many genetically differentiated populations, which can not be distinguished by morphological characteristics, among which B and Q biotype were widely distributed and well-studied. Many researches proved that B. tabaci biotype Q has better survival than biotype B due to higher tolerance to extreme temperature and greater resistance to insecticides, and biotype Q has spread worldwidely. Using two methods of mtCOI and SCAR molecular markers, the present study was, therefore, initiated to extensively and systematically survey the newly introduced biotype Q, which will unveil its significance and current distribution in the main agricultural ecosystems across the country. Furthermore, valid percentage of biotype Q in different B. tabaci populations will be determined and the phylogenetic analysis based on mtCOI sequences was given to infer the original lacation of B. tabaci.biotype Q in China. The main results and conclusion were as follows,1. In the four years from 2003 to 2007, B. tabaci biotype Q had become widely dispersed, it was only in kunming (Yunnan Province) that biotype Q was firstly discovered in 2003, however, B. tabaci biotype Q was found in 20 populations by the two molecular markers from Jingzhou, Xiangfan and Wuhan (Hubei Province), Laiyang and Taian (Shandong Province), Sanya (Hainan Province), Guilin and Nanning (Guangxi Autonomous Region), Guiyang (Guizhou Province), Hangzhou and Ningbo (Zhejiang Province), Xiangtan and Yueyang (Hunan Province), Yangzhou (Jiangsu Province), Xinxiang (Henan Province), Baoji (Shaanxi Province), Jiuquan (Gansu Province), Yuncheng (Shanxi Province), Fuzhou (Fujian Province) and Tianjin. The biotype Q was not found in the four populations from Tulufan (Xinjiang Uigur Autonomous Region), Chengde and Langfang (Hebei province) and Hefei (Anhui Province).2. The invasive status of B. tabaci biotype Q in different regions was various: The biotype Q has successfully invaded majority of southeastern provinces, where traffic and transportation are comparatively frequent than other provinces in the country. Moreover, the proportion of biotype Q is higher than 50% in most of these provinces. In addition, the biotype Q is also distributed in several under-developed western provinces (e.g., Gansu, Shaanxi, Guizhou, Guangxi), but with lesser than 50% proportion. The distribution of B. tabaci biotype Q in China was related with human activities.3. There is high probability that biotype Q will further spread to other regions by displacing biotype B. Using mtCOI sequencing, the biotype Q was detected in 20 populations in which biotype B was also found except in the population from Fuzhou (Fujian Province). There is high probability that biotype Q will further spread to other regions by displacing the biotype B, due to its greater tolerance to extreme temperature and resistance to insecticides than the biotype B. 4. Phylogenetic analysis based on mtCOI sequences:The GenBank accession numbers of the sequences representing the different geographic populations of the country were FJ375346-FJ375358, FJ594428-FJ594434 and FJ647195-FJ647217. The phylogenetic tree also showed that: twenty sequences of mt CO1 gene (FJ375346-FJ375358, FJ594428-FJ59 4434) of B. tabaci in China were grouped with individuals of biotype Q from Spain and other 6 countries, forming a sub-clade, with more . The other sub-clade contained biotype Q from Israel (DQ365878), Cyprus (DQ365877) and Turkey (AF342776) with the support value of 95%. It was inferred that B. tabaci biotype Q in China was introduced from western Mediterranean countries.