Research On Transmission Of Tomato Yellow Leaf Curl Virus By B And Q Bemisia Tabaci With Characteristics Of Plant Defense

The whitefly, Bemisia tabaci (Hemiptera:Aleyrodidae), is one of the most widely distributed agricultural pests. In recent years, B, tabaci Q has invaded China, and Q has gradually displaced B in many areas now. In a number of regions of the world, invasion by B and/or Q has been followed by outbreaks of tomato yellow leaf curl virus (TYLCV).In this study, we investigated the interaction of whitefly-plant-virus. We compared the plant defense responses induced by B and Q Bemisia tabaci with virus or not, and determined the different effects of increased plant defense on whiteflies, to find the mechnism of the mutualistic relationship between TYLCV and Q Bemisia tabaci.We quantified the jasmonic acid (JA) and salicylic acid (SA) titers and relative gene expression of JA and SA in tomato leaves that were infested with viruliferous or non-viruliferous B and Q. Jasmonic acid content was significantly lower in leaves infested with viruliferous Q than in noninfested leaves or in leaves infested with nonviruliferous Q, viruliferous B, or nonviruliferous B. The expression of LOX and PI Ⅱ genes showed the same trend, i.e., the expression was much lower with viruliferous Q than with nonviruliferous Q, viruliferous B, or nonviruliferous B. SA titer was always higher in leaves that were infested with viruliferous B than with viruliferous Q, whereas the SA titer did not differ between leaves infested with non-viruliferous B and Q. The relative gene expression of SA signaling was increased by feeding of viruliferous B but was not increased by feeding of viruliferous Q.We examined the performance and effects of B. tabaci B and Q on plants previously attacked by nonviruliferous or viruliferous Q or B. Fecundity and longevity were similar for nonviruliferous whiteflies on plants previously attacked by nonviruliferous whiteflies. Fecundity and longevity were also similar for viruliferous Q on plants previously attacked by viruliferous B. In contrast, fecundity and longevity were greater for viruliferous B and Q on plants previously attacked by viruliferous Q. With regard to protease inhibitor (PI), PI activity was significantly lower in leaves infested with viruliferous Q than in noninfested leaves or in leaves infested with nonviruliferous Q, viruliferous B, or nonviruliferous B.The life history traits of B and Q were adversely affected on SA-treated plants. On SA-treated plants, both B and Q had lower fecundity, shorter longevity, longer developmental time and lower survival rate than on untreated plants. Compared with whiteflies feeding on control plants, those feeding on SA-treated plants had fewer oocytes and slower ovary development. On SA-treated plants, viruliferous B had fewer oocytes than viruliferous Q. Exogenous SA also increased the content and changed the composition of plant volatiles, resulting in altered choice behavior of whiteflies.The exogenous JA treatment showed reduced whitefly fecundity, longevity, developmental time, and survival rate. Viruliferous Q showed a higher performance than nonviruliferous Q, viruliferous B, or nonviruliferous B. Exogenous JA also increased the content and changed the composition of plant volatiles, resulting in altered choice behavior of whiteflies. The JA-overexpress plant was used to determine the difference defense response induced by non-viruliferous and viruliferous Q. The results showed that non-viruliferous Q reduced endogenous JA and induced endogenous SA However, viruliferous Q greatly reduced the endogenous JA while not induced endogenous SA compared with non-viruliferous Q. Infestion of non-viruliferous Q increased level of plant volatile substance. In contrast, infestion of viruliferous Q didn’t induce the content but changed the component of plant volatiles. Furthermore, on JA-overexpress plant and control plant, viruliferous Q B. tabaci showed a higher fecundity, longevity and survival rate but a lower preference than non-viruliferous Q B. tabaci.