| Wheat aphid belong to Aphididae(Hemiptera), which is one of the important pests on wheat. In China, the majority of wheat aphid were Sitobion avenae, Schizaphis graminum, Rhopalosiphum padi, Acyrthosiphon dirhodum. They stay in leaves stems, wheatears, and feed primarily on wheat by sucking, at the same time they excrete water and honeydew, which causes nosomycosis. Sitobion avenae and Schizaphis graminum can diffuse the wheat yellow dwarf. Wheat aphid lead to the production drawdown of wheat. Aphidius gifuensis(Ashmead) is one of the important enemies of aphid, which can parasitize Myzus persicae(Sulzer), Sitobion avenae(Fabricius), Lipaphis erysimi(Kaltenbach), Schizaphis graminum(Rondani) and so on.At present study, we use A.gifuensis, Schizaphis graminum and Sitobion avenae as the material. We observe the biological characters of A.gifuensis, the effect of genes and protective and detoxification enzymes at some periods in Schizaphis graminum, which were parasitized by A.gifuensis. We probe the change of Sitobion avenae and Schizaphis graminum after parasitism and the breeding technology of A.gifuensis, from the view of biology, physiology and molecular biology. Utilize the method of real-time PCR to observe the expression of immunity-related genes. We study the relationship between parasitic wasp and host, the control of pest by natural enemy, and provide more effective methods to control pest. The main results are as follows:(1) The longevity of A.gifuensis was gradually shorter with increasing temperature under the condition of the same food. At the same temperature,the longevity of A.gifuensis which not feeding honey water was shortest, the life of a feeding 5% honey water life expectancy. In all processing, A.gifuensis with 5% honey water 4 ℃ refrigerator,the average life expectancy of up to 27.05 days, but not lively, almost no movement. The longevity of A.gifuensis was the shortest without food at 27 ℃, only for average 21 h. Female life and drone life and no significant difference.(2)Based on the longevity of A.gifuensis was up to 30 d at 4 ℃, we study the effect of parasitism rate by 4 ℃. The results show that the parasitic ability of A.gifuensis had no significant differences between the infections and the controls in 4 ℃ under the condition of refrigeration 1, 4, 7, 10 d. The result shows that A.gifuensis could still normal breeding after 4 ℃ refrigerated processing in a suitable environment.(3)The mummy in 4 ℃ cold storage time can reach 31 days. With the increasing of days, the emergence rate had declined, refrigerated 7 days after eclosion rate significantly reduced 31.67%, refrigerated 31 d after eclosion rate is only 8.33%. The mummy rate was significantly lower than control, at refrigerate 1, 4, 7, 10 d. Except the stage at 13 d and 16 d, The mummy rate was no significant difference.(4)The smaller the age aphid which was parasitized by A.gifuensis had the longest mummy duration and longest emergence duration. In 1st instar of Schizaphis graminum, the mummy duration of the parasitoid was 8.26 d and the emergence duration was 12.29 d. In 1st instar of Sitobion avenae, the mummy duration of the parasitoid was 11.25 d and the emergence duration was 16.23 d. The mummy duration and emergence duration in 1st instar of Schizaphis graminum were shorter than Sitobion avenae.(5)The study found that in mixed host selective trials, by A.gifuensis and Sitobion avenae or Schizaphis graminum. The mixed hosts show that A.gifuensis which emerge from could parasitze both of two hosts, what’s more, the parasitism rate and superparasitism rate had no significant differences between Schizaphis graminum and Sitobion avenae.(6)Utilize the method of spectrophotometric to observe fluctuations about the activity of protective enzymes and the detoxification enzymes changes at some periods in Schizaphis graminum, found that after A.gifuensis was parasitic acetylcholinesterase(ACh E) activity in 12 h, 72 h was significantly lower than the control group. Acid phosphatase(ACP) activity in 3 h, 5 h significantly lower than the control group, but within 24 h in ACP activity was significantly higher than control. The changes of alkaline phosphatase(AKP) activity there was no significant difference with control group, only after 10 h, 12 h AKP activity slightly higher than the control. Catalase(CAT) activity in 24 h is significantly higher than control. Peroxidase(POD) activity at 6 h was significantly lower than control, is significantly higher than control group in 24 h. Total superoxide dismutase(T-SOD) activity compared with the control group there was no significant change.(7)By real-time fluorescent quantitative PCR analysis, we found that the relative expression of some genes was lower than the controls after Schizaphis graminum, which were parasitized by A.gifuensis, these genes include serine protease 34-like, serine protease inhibitor 4, serine protease inhibitor 32, Collectin 10, Prophenoloxidase, Prophenoloxidase A3, prophenoloxidase activating factor, spatzle 6, Toll receptor 13, Toll receptor 6, nitric oxide synthase, nitric oxide synthase interacting protein, Thioredoxin-like protein 4A, thioredoxin reductase 1, Mn superoxidase dismutase. And the relative expression of some genes was higher than the control group after parasitized by A.gifuensis, these genes include Scavenger receptor B, draper,hemolin and peroxidase. These results futher demonstrate that A.gifuensis regulated the expression of genes of Schizaphis graminum and disrupt hosts cellular immune response by 4 main groups, including signal recognition, signal modulation and amplification, signal transduction, and effector genes. |
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