Physiological and Biochemical Responses to Sublethal Concentrations of the Novel Pyropene Insecticide, Afidopyropen, in Whitefly Bemisia tabaci MED (Q Biotype)

Bemisia tabaci is a devastating agricultural insect pest worldwide, and B. tabaci MED (formerly biotype ‘Q’) threatens the production of horticultural and economic crops in China as a growing number of cases of insecticide resistance have issued, highlighting the requirement for alternative methods and measures of pest management. In the present work, the toxicities of eight popular chemical agents, including the novel pyropene insecticide afidopyropen, on adults of B. tabaci MED were determined, and then physiological and biochemical responses to sublethal concentrations were confirmed. Among all tested chemical agents, afidopyropen exhibited the highest toxicity to adult whiteflies (LC50: 7.38 mg/L). The sublethal effects of afidopyropen were studied at two sublethal concentrations, LC10 (0.53 mg/L) and LC25 (1.84 mg/L), and LC25 treatment extended the duration of growth stages and reduced viabilities in the stages of nymphal, pseudopupae, and adults. The egg-laying days and eggs laid per female were also decreased significantly, as was hatchability in the LC25 treatment. Metabolic enzyme assays suggested that the sublethal effects of LC25 treatment could be ascribable to enhanced detoxification mediated by glutathione S-transferase. In summary, our findings indicate that afidopyropen can be used as a chemical agent for the management of B. tabaci MED whiteflies.

Impacts of cucurbit chlorotic yellows virus (CCYV) on biological characteristics of its vector Bemisia tabaci

It is known that plant viruses, to facilitate their transmission, can change the phenotypes and defense pathways of the host plants and the performance of their vectors. Cucurbit chlorotic yellows virus (CCYV), a newly reported virus occurring on cucurbit plants and many other plant species, is transmitted specifically by Middle East-Minor Asia 1 (B biotype) and Mediterranean (Q biotype) cryptic species of whitefly, Bemisia tabaci (Gennadius), in a semipersistent manner. This study evaluated the direct and indirect effects of CCYV on B. tabaci biology to better understand the plant-virus-vector interaction. By using CCYV-B. tabaci-cucumber as the model, we investigated whether or how a semipersistent plant virus impacts the biology of its whitefly vectors. CCYV mRNA were detectable in nymphs from 1st to 4th instars and adults of B. tabaci with different titers. Female nymph duration and female adult longevity greatly extended on CCYV-infected plants, but male nymph duration and male adult longevity were not significantly influenced. In addition, on CCYV-infected plants, the body length and oviposition of adult B. tabaci increased, but the hatching rates of eggs and survival rates of different stages were not affected. Most interestingly, the sex ratio (male:female) significantly reduced to 0.506:1 in whitefly populations on CCYV-infected plants, while the ratio remained about 0.979:1 on healthy plants. These results indicated that CCYV can significantly impact the biological characteristics of its vector B. tabaci through the host plants. It is speculated that CCYV and B. tabaci have established a typical mutualist relationship mediated by host plants.

Overview of the occurrence and prevention of Bemisia tabaci invasion in China

摘要Biological invasion refers to the process of invading into another new environment through natural or man-made means from the original place of existence,which includes several stages of introduction, colonization, incubation, diffusion and outbreak.Bemisia tabaci is a worldwide important agricultural pest composed of multiple biotypes. Studies have confirmed that the B biotype Bemisia tabaci that invaded China has been genetically differentiated, and the Q biotype Bemisia tabaci has replaced the B biotype in most areas of China. Bemisia tabaci has become the dominant biotype in the field.

Tomato Chlorosis Virus Infection Facilitates Bemisia tabaci MED Reproduction by Elevating Vitellogenin Expression

Transmission of plant pathogenic viruses mostly relies on insect vectors. Plant virus could enhance its transmission by modulating the vector. Previously, we showed that feeding on virus infected plants can promote the reproduction of the sweet potato whitefly, Bemisia tabaci MED (Q biotype). In this study, using a whitefly-Tomato chlorosis virus (ToCV)-tomato system, we investigated how ToCV modulates B. tabaci MED reproduction to facilitate its spread. Here, we hypothesized that ToCV-infected tomato plants would increase B. tabaci MED fecundity via elevated vitellogenin (Vg) gene expression. As a result, fecundity and the relative expression of B. tabaci MED Vg was measured on ToCV-infected and uninfected tomato plants on days 4, 8, 12, 16, 20 and 24. The role of Vg on B. tabaci MED reproduction was examined in the presence and absence of ToCV using dietary RNAi. ToCV infection significantly increased B. tabaci MED fecundity on days 12, 16 and 20, and elevated Vg expression on days 8, 12 and 16. Both ovarian development and fecundity of B. tabaci MED were suppressed when Vg was silenced with or without ToCV infection. These combined results suggest that ToCV infection increases B. tabaci MED fecundity via elevated Vg expression.

Non-transmissibility of Pepper whitefly borne vein yellows virus (PeWBVYV) by the Mediterranean species of Bemisia tabaci and identification of a candidate insect receptor protein for poleroviruses

Recent reports of transmission of poleroviruses by whiteflies is indicative of evolution of new virus-vector relationships. Pepper whitefly-borne vein yellows virus (PeWBVYV), was the first report of a polerovirus infecting pepper in Israel which was transmitted by whiteflies (MEAM1) and not aphids. This study reports the inability of the Mediterranean species (MED, Q biotype) of B. tabaci to transmit PeWBVYV. However we show that non-transmission of PeWBVYV by MED is not due to the lack of interaction with the GroEL protein of the Hamiltonella symbiont. Although not transmitted by MED, PeWBVYV was detected in its hemolymph, indicating its translocation across the MED midgut barrier. The aphid transmitted Pepper vein yellows virus 2 (PeVYV-2) was also detected in the hemolymph of MEAM1 whiteflies but PeWBVYV could not be detected in the aphid hemolymph. Interestingly, relative amounts of PeWBVYV in the hemolymph of the, MED was much lower than in hemolymph of MEAM1 whiteflies. We also identified a candidate receptor protein, complement component 1Q sub-complement binding protein (C1QBP) which interacts with the capsid proteins of PeWBVYV and PeVYV-2 but not with the whitefly transmitted Tomato yellow leaf curl virus by a yeast two-hybrid approach using the minor capsid protein (RTD) as bait to screen for interacting proteins against the whitefly cDNA library. C1QBP, is a known receptor of bacterial and viral pathogens but this is the first report of its interaction with a plant virus.

A proteomic approach reveals possible molecular mechanisms and roles for endosymbiotic bacteria in begomovirus transmission by whiteflies

Background Many plant viruses are vector-borne and depend on arthropods for transmission between host plants. Begomoviruses, the largest, most damaging and emerging group of plant viruses, infect hundreds of plant species, and new virus species of the group are discovered each year. Begomoviruses are transmitted by members of the whitefly Bemisia tabaci species complex in a persistent-circulative manner. Tomato yellow leaf curl virus (TYLCV) is one of the most devastating begomoviruses worldwide and causes major losses in tomato crops, as well as in many agriculturally important plant species. Different B. tabaci populations vary in their virus transmission abilities; however, the causes for these variations are attributed among others to genetic differences among vector populations, as well as to differences in the bacterial symbionts housed within B. tabaci. Results Here, we performed discovery proteomic analyses in 9 whitefly populations from both Middle East Asia Minor I (MEAM1, formerly known as B biotype) and Mediterranean (MED, formerly known as Q biotype) species. We analysed our proteomic results on the basis of the different TYLCV transmission abilities of the various populations included in the study. The results provide the first comprehensive list of candidate insect and bacterial symbiont (mainly Rickettsia) proteins associated with virus transmission. Conclusions Our data demonstrate that the proteomic signatures of better vector populations differ considerably when compared with less efficient vector populations in the 2 whitefly species tested in this study. While MEAM1 efficient vector populations have a more lenient immune system, the Q efficient vector populations have higher abundance of proteins possibly implicated in virus passage through cells. Both species show a strong link of the facultative symbiont Rickettsia to virus transmission.