| The whitefly Bemisia tabaci is an important pest,that is distributed widely in the world. It is considered taxonomically as a species complex which contained some destructive pests. B. tabaci also caused serious agricultural losses on vegetables, flowers and any other economics crop production in many parts of China, especially by the two invasive cryptic species, Middle East-Asia Minor (MEAM1) and Mediterranean(MED). The questions, including determination the distribution of different cryptic species, the host range and damage from invasive and indigenous, and the biochemical reaction mechanism to insecticide resistance, should have been thought worthy of attention. In this paper, we collected and analyzed a series of field samplings in our country, and the identification, distribution and population genetic differentiation,harm of host plants, transcriptome gene sequencing and gene function analysis, insecticide resistance monitoring and the biochemical reactions of detoxification enzymes in the resistant of B. tabaci were studied. The results are summarized as follows:Using the method of mtDNA COI gene sequencing and cDNA-AFLP analysis, we confirmed that two invasive crytpic species (MEAM1and MED) and4indigenous cryptic species (Asia Ⅱ1, Asia Ⅱ3, China3,and Asia Ⅱ7) of the B. tabaci complex were found in different parts of China in this survey. The B. tabaci MEAM1and MED have invaded and established in the field, become dominant in the Yangtze River Valley and eastern coastal areas. Four indigenous B. tabaci species AsiaⅡ3, Asia Ⅱ1, China3, and Asia Ⅱ7were found from six locations and they showed a much narrower host range than that of MEAMl or MED. Amplification of the cDNA of19B. tabaci populations, the MED showed a lower degree of similarity than MEAM1.It suggested to be of benefit for the invasion of MED than MEAMl,by the high level of genetic diversity.A rapid, high-throughput cryptic species identification between MED and MEAM1,depend on TaqMan allele-selective PCR, has been successfully established. The method realized that lots of samples of cryptic species was identified correctly with different invasive cryptic species between MEAM1and Med, without DNA sequencing. The transcriptome of B.tabaci MEAM1and MED cryptic species have been sequenced,and we have acquired91,518Unigenes genes by analysis of gene expression profiles differences, which about1100-2100Unigene is up-regulated or down-regulated. It provided a large number of functional data information for further analysis of the genetic structure of whitefly.The resistance of different genetic populations of B.tabaci to imidacloprid was evaluated with leaf-dip bioassay. The results showed that the resistance level to imidacloprid in MED is higher than MEAMl,and have developed rapidly in recent years. The4types of detoxification enzyme activity have been measured,and it confirmed that Multiple Function Oxidase(MFO) play an important role in the process of resistance to imidacloprid, glutathione S-transferase(GSTs) may have part of functional reaction, but the carboxylesterase(CarE) and acetylcholinesterase(AChE) have no obvious function in the progress. The bioactivity of Spinosad and Abamectin on different stages of B. tabaci was measured. The results showed that that abamectin and spinosad have high insecticidal activity on nymphs and adults, and no effect on eggs between controls. Compared with spinosad, abamectin could be recommended as a good rotation-selected insecticide in field control of B. tabaci with higher sensitivity. Both of two insecticides could induce insect detoxifying enzymes system to stress reaction. But the reaction tendency and change of CarE, AChE and GSTs activities were different. It obviously observed that AChE activity have a progress of inhibition, induction and inhibition again, by Abamectin at the range of reaction. While CarE activities could be induced by spinosad from reaction beginning.Impacts of six common insecticides on B. tabaci in field efficiency trial and bioassay were tested in cucumber. The results showed that corrected mortality of Abamectin was78.8%in prevention and treatment of B. tabaci MED, which is best in6insecticides in the test. Compared with the MEAM1, MED cryptic species had developed more higher resistant level to Abamectin, Matrine, Acetamiprid, Imidacloprid, Kingbo, Cypermethrin with the resistant ratio of4.40-47.69. Cypermethrin have an high level of resistance on B. tabaci MED, and not fit to ben a insecticide to control the pest. The use of screening test from Botanical Pesticides showed that1.2%matrine nicotine and0.6%matrine pesticide have good insecticidal effect on B. tabaci MED... |
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