Zhejiang Type B And Type B Zhj-1 Tobacco Whitefly Diversity And Function Of Symbiotic Bacteria

The whitefly Bemisia tabaci Gennadius (Homoptera: Aleyrodidae ) is a worldwide pest of vegetable, ornamental, and field crops. Bemisia tabaci is a highly cryptic group of sibling species composed by a number of biotypes. Among these biotypes, the B biotype has a broader host range, is highly fecund, and causes serious plant disorders not caused by other B. tabaci biotypes. Whiteflies and other homopterans have the unique ability to feed exclusively on phloem sap, which is rich in carbohydrates and deficient in essential amino acids. This ability has been undoubtedly linked to the endosymbionts of these insects. Endosymbionts can supplement their host's diet with essential amino acids and are essential for the development and reproduction of their insect hosts. Endosymbionts of insects are usually categorized into two types, the primary (P-) endosymbionts, which are harbored in specialized host cells called bacteriocytes and the secondary (S-) endosymbionts. S-endosymbionts are not restricted to bacteriocytes, but are present in almost all types of cells of the host insects. In addition to primary endosymbiont Candidatus Portiera aleyrodidarum, B. tabaci may also harbor several S-endosymbionts, such as Candidatus Hamiltonella defensa(Enterobacteriaceae), Wolbachia, Arsenophonus, Cardinium hertigii, Fritschea bemisiae and Rickettsia.Endosymbionts have a variety of effects on their hosts. Endosymbionts may play a direct and/or indirect role in the evolution of their insect hosts. Genetic changes in B. tabaci endosymbionts and/or variations of the endosymbionts in different biotypes of B. tabaci may play a functional role in the evolution of biotypes of this whitefly.In this study, I first used universal primers and specific primers to detect the endosymbionts of B and ZHJ-1 biotypes of B. tabaci. Then, to investigate the function of these endosymbionts in the two biotypes of B. tabaci, I selected three antibiotics, tetracycline, ampicillin trihydrate and rifampicin, to feed adult whiteflies and evaluated the fitness of their offspring on cotton plants.(1) Four different 16S rDNA sequences were detected, cloned and sequenced with the universal primers 27F and 1494R. Compared with all other known 16S rDNA sequences, the endosymbionts were identified as the primary symbiont Portiera aleyrodidarum, and these secondary endosymbiont Hamiltonella defensa, Wolbachia and Arsenophonus.(2) All B. tabaci examined harbored a common primary symbiont Portiera aleyrodidarum and secondary endosymbiont Fritschea bemisiae. However, the secondary endosymbiont Hamiltonella defensa and Rickettsia were detected only in B biotype population but none in ZHJ-1, while Wolbachia and Arsenophonus were detected only in ZHJ-1 biotype. An analysis of a phylogenetic tree of primary endosymbionts based on 16S rDNA indicated that ZHJ-1 is indigenous to Zhejiang while the B biotype is alien to China.(3) The three antibiotics used did not remove the primary endosymbiont Portiera aleyrodidarum but were capable of removing Hamiltonella defensa, Wolbachia and Arsenophonus. In the B biotype, treatments of adults with tetracycline or ampicillin trihydrate accelerated the development and increased the survival of their offspring, while treatment of adults with rifampicin significantly retarded the development of their offspring but did not affect their survival. In ZHJ-1, treatments of adults with tetracycline or ampicillin trihydrate also accelerated the development of their offspring but did not significantly affect their survival, while treatment of adults with rifampicin significantly retarded the development and reduced the survival of their offspring.