Vector-Virus Mutualism Accelerates Population Increase of an Invasive Whitefly

The relationships between plant viruses, their herbivore vectors and host plants can be beneficial, neutral, or antagonistic, depending on the species involved. This variation in relationships may affect the process of biological invasion and the displacement of indigenous species by invaders when the invasive and indigenous organisms occur with niche overlap but differ in the interactions. The notorious invasive B biotype of the whitefly complex Bemisia tabaci entered China in the late 1990s and is now the predominant or only biotype in many regions of the country. Tobacco curly shoot virus (TbCSV) and Tomato yellow leaf curl China virus (TYLCCNV) are two whitefly-transmitted begomoviruses that have become widespread recently in south China. We compared the performance of the invasive B and indigenous ZHJ1 whitefly biotypes on healthy, TbCSV-infected and TYLCCNV-infected tobacco plants. Compared to its performance on healthy plants, the invasive B biotype increased its fecundity and longevity by 12 and 6 fold when feeding on TbCSV-infected plants, and by 18 and 7 fold when feeding on TYLCCNV-infected plants. Population density of the B biotype on TbCSV- and TYLCCNV-infected plants reached 2 and 13 times that on healthy plants respectively in 56 days. In contrast, the indigenous ZHJ1 performed similarly on healthy and virus-infected plants. Virus-infection status of the whiteflies per se of both biotypes showed limited effects on performance of vectors on cotton, a nonhost plant of the viruses. The indirect mutualism between the B biotype whitefly and these viruses via their host plants, and the apparent lack of such mutualism for the indigenous whitefly, may contribute to the ability of the B whitefly biotype to invade, the displacement of indigenous whiteflies, and the disease pandemics of the viruses associated with this vector

Spectroscopic assignments of Ti3+ and Ti4+ in titanium-doped OH- free low-silica calcium aluminosilicate glass and role of structural defects on the observed long lifetime and high fluorescence of Ti3+ ions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)In this work we present the spectroscopic assignments of Ti3+ and Ti4+ in titanium-doped OH- free low-silica calcium aluminosilicate glass and the influence of structural defects on the observed long lifetime and high fluorescence intensity of Ti3+ ions. Measurements were performed with electron-spin resonance (ESR), time resolved luminescence, ultraviolet-visible (UV-VIS) optical excitation and emission spectra, and conventional optical absorption and photoconductivity. The ESR data showed that the Ti3+/Ti4+ ratio increases with the doping concentration and that the Ti3+ ions are in distorted octahedral sites. The assignment of the Ti3+ and Ti4+ emission bands derived from the spectroscopic results allowed us to propose a model explaining the mechanisms involved in the luminescence processes. The long lifetime of the Ti3+ emission around 650 nm (on the order of 170 mu s) is about two orders of magnitude higher than the values found in the literature and was associated to the trapping of the excited electrons by the glass defects followed by detrapping via defect recombination. In conclusion, the combination of several techniques permitted a comprehensive characterization of the Ti ions in this OH- free glass.7822Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundacao AraucariaCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CNRS-UCBLyon1Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CAPES [565/07