Screening Of Resistance Of Two Species Of Trichogramma To Non-lepidoptera Target Pesticides And The Expression Of P450 Gene

At present,the use of Trichogramma to control rice lepidopteran pests has Trichogramma n promoted throughout the country.The use of Trichogramma for pest control has the advantages of safety,no pollution to the environment and no residue of products.It plays an irreplaceable role in reducing pest damage and sustainable agricultural development.The complicated environment in the rice field leads to the mixed occurrence of diseases and insect pests in the later stages of rice growth,and these diseases and insect pests(such as rice blast,rice curl disease,sheath blight,and rice planthopper,etc.)also occur simultaneously during the Trichogramma release process.The application of chemical pesticides is still the main control measure,but Trichogramma inevitably comes into direct or indirect contact with pesticides.Pesticides not only to Trichogramma toxic effect,but also reduce the rate of emergence of Trichogramma,parasitic capacity,the proportion of female life and search capabilities,seriously reduce the control effect.Biological control combined with chemical pesticides is a direction of integrated pest management.Therefore,breeding resistant Trichogramma species has important practical application value.In view of this,this paper determined the toxicity and safety evaluation of seven kinds of pesticides commonly used in paddy fields on Trichogramma japonicum and Trichogramma chilonis.On this basis,four kinds of insecticides were used to cultivate two resistant species of Trichogramma,and the biological characteristics of the two species of Trichogramma during the selecting process were investigated.At the same time,the role of P450 gene in the development of drug resistance of Trichogramma was discussed,which provided a theoretical basis for the drug resistance mechanism of Trichogramma.The main results are as follows:1.Toxicity and safety evaluation of seven pesticides on the growth and pupation stage of two Trichogramma species.The acute toxicity of insecticides(imidacloprid,thiamethoxam,thiazinone,nitenpyram,and pymetrozine)and fungicides(ricegrass,tricyclazole)to T.japonicum and T.chilonis.Two of the fungicides and pymetrozine are safe for both Trichogramma,and the other four pesticides are highly toxic.Thiamethoxam has the highest toxic for two Trichogramma,which is of moderate risk.Imidacloprid,thiazinone,and nitenpyram are of medium risk to T.japonicum,and low risk to T.chilonis.T.japonicum is more sensitive to pesticides than T.chilonis and Trichogramma pupae is less sensitive than adults.2.Result of resistance test of T.japonicum and T.chilonisPesticide resistance of T.japonicum is in the order of imidacloprid > nitenpyram >thiamethoxam > thiamethoxam population,the resistance multiples are 17.98,7.41,4.72 respectively and 2.5.Pesticide resistance of T.chilonis was in the order of imidacloprid > thiamethoxam > nitenpyram > thiamethoxam,the resistance multiples were 8.8,6.9,5.67 and 4.43.The imidacloprid-resistant population of the T.japonicum was cross-resistant to enanthimidine,while the thiamethoxazine-resistant population was cross-resistant to low imidacloprid.The imidacloprid-resistant population of the T.chilonis was cross-resistant to thiamethoxazine,while the enosine-resistant population was cross-resistant to thiamethoxazine.3.Changes in biological characteristics of resistant TrichogrammaLong-term treatment with the four pesticides significantly reduced the rate of emergence and resulted in malformation of T.japonicum and T.chilonis.However,with the increase of screening times,the emergence rate gradually increased and the malformation rate significantly decreased.The parasitism of the two species of Trichogramma increased after treatment with the pesticides thiamethoxazine and enoxamide,while imidacloprid and thiazinone decreased the parasitism.The emergence rate and female ratio of offspring of all populations were lower than those of normal.Pesticides had a persistent effect on the offspring of Trichogramma,and the parasitism of imidacloprid and enoxamide recovery groups decreased.4.Screening of Internal Reference Genes of Trichogramma.The stability of nine candidate reference genes(EF2,RPS23,RPL13,RPL44,MDH,EIF3 F,ZFP268,MP20 and ATP5F1A)in T.chilonis was determined.The stable internal reference genes under different developmental durations were EF2 and RPS23,the stable internal reference genes under different feeding conditions were ZFP268 and EF2,the stable internal reference genes under different temperature conditions were ZFP268 and RPL13,and the stable internal reference genes under different pesticide treatments were determined.The stable internal reference genes were EF2 and RPL44.5.The effect of P450 geneCYP4 clabe(CYP4C1 and CYP4G15)and CYP3 clabe(CYPA14,CYP6A2 and CYP9E2)were up-regulated in the P450 genes of T.japonicum,while CYP4 clabe(CYP4AA),CYP4 clabe(CYP4AA1),CYP3 clabe(CYP6A2,CYP9E2,CYP9E2,CYP9P3,CYP9AG3 and CYP9AG4),CYP2 clabe(CYP307A1)and Mito clabe(CYP315A1)were up-regulated in the P450 genes of T.chilonis.Among them,CYP9P3 and CYP307A1 may be involved in the interaction resistance between imidacloprid and enoxamide;CYP4C1,CYP4G15 and CYP6K1 are involved in the formation of thiazide and enoxamide interaction resistance;CYP4AA1,CYP6A2 and CYP9E2 are involved in the formation of thiazide and imidacloprid interaction resistance.