| Phyllotreta striolata (Fabricius) which belongs to Coleoptera, Chrysomelidae is an important pest of cruciferous vegetables. Because of its strong reproductive ability and the harm to plant and root caused by adults and larvae, it is quite difficult to control phyllotreta striolata which has had varying degrees of resistance towards many pesticides in recent years, and it has become a vegetable pest that is the most difficult to prevent in southern China, Phyllotreta striolata is the focus of vegetable pest control. In the existing pesticides to prevent phyllotreta striolata, organophosphorus pesticides, for example chlorpyrifos and profenofos, still have a good effect. In this paper, by evaluating six kinds of pesticides toxicities towards phyllotreta striolata in five regions of Hunan province,as well as the differences of enzymatic activity between various phyllotreta striolata species in Hunan, physiological resistance mechanism of phyllotreta striolata towards organophosphorus pesticides and some relevant problems are discussed, with the help of gene fragments of acetylcholine esterase in phyllotreta striolata clonced in molecular biology methods.1. Resistance Monitoring of phyllotreta striolata in Hunan Province. By evaluating the toxicity of six kinds of pesticides towards phyllotreta striolata adults in five regions of Hunan province, it shows that:the virulence of chlorpyrifos, profenofos, Pyridaben and Rotenone is higher, and their LC50between40.592-62.504,46.474-66.449,68.103-125.849,60.249-81.574mg/L; The toxicity of acetamiprid and imidacloprid is relatively low, and their LC50between134.573-248.511and157.065-266.446mg/L. Through the analysis of toxicity, profenofos, pyridaben and rotenone are the best pesticides for controlling phyllotreta striolata.2. Testing results of enzymatic activity of phyllotreta striolata in hunan areas. After determination, it has been found that there is little difference of activity among acetylcholin esterase (AChE)> carboxylesterase (CarE) and glutathione S-transferase (GSTs) for phyllotreta striolata species in five regions of hunan, such as Yue Yang, Xiang Tan, Chang Sha, Chang De and Lou Di, basically within1.3times. AChE activity of the five species decreases successively while the activity of CarE and GSTs increases in sequence, which is consistent with the toxicity of Chorpyriphos and profenofos towards phyllotreta striolata. It is predicted that the resistance of phyllotreta striolata towards chorpyriphos and profenofos is concerned with the drop of AChE activity and the increase of CarE and GSTs activity.3. The RNA of the minimum resistancethe and the highest resistance population to chlorpyrifos and profenofos are extracted and acetycholinesterase gene fragment are cloned, in order to compare the difference of partial acetycholinesterase gene fragments in phyllotreta striolata of diverse drug-resistance. The resulce from two populations may not be changed, thus speculating the different resistance of different phyllotreta striolata populations towards chlorpyrifos and profenofos is caused by different capacity of different species to metabolize chlorpyrifos and profenofos. |
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