Study On The Biochemical Mechanism Of Insecticide Sensitivity And Virulent Shift Of Nilaparvata Lugens(St(?)l)

In this thesis, the BPH field population, biotypeâ…¡and biotype Bangladesh wereused as the study object, the three populations were induced with imidacloprid andmalathion, BPH biotypeâ…¡and biotype Bangladesh reared on IR36 and RHTrespectively. The activity of esterase(EST), glutathione S-transferases(GST) and mixedfunction oxidases (MFO) were determined after inducing with imidacioprid andmalathion and rearing on IR36 and RHT every generation, the biochemical mechanismof the BPH insecticide sensitivity and virulent shift was discussed initially. The mainresults were as follow:(1) The results of BPH field population, biotypeâ…¡and biotype Bangladeshinducing with imidacioprid by rice-stem dipping method indicated that the LC₅₀ valueswere 13.0357, 19.4374 and 5.1649 mg/L respectively, the resistance levels were 144.83folds, 215.95 folds and 57.38 folds respectively (The order of sensitivity: biotypeBangladesh＜field population＜biotypeâ…¡), The results of BPH field population, andbiotype Bangladesh inducing with malathion by topical appilication method indicatedthat the LD₅₀ values were 0.5584 and 0.3207μg·pest^-1 respectively, the resistance levelswere 50.76 folds and 29.15 folds respectively (The order of sensitivity: biotypeBangladesh＜field population). While Used LC₅₀ or LD₅₀ values of last generationinducing, after imidacloprid inducing, the ratio of F₃ to F₀ in field population, biotypeâ…¡and biotype Bangladesh of 3rd generation were 1.41, 1.19 and 5.34 respectively, theorder of resistance is rising from the slow to high: biotypeⅡ＜field population＜Bangladesh. After malathion inducing, the ratio of F₂ to F₀ in field population, and biotype Bangladesh of 2nd generation were 1.06 and 1.13 respectively, the order ofresistance is rising from the slow to high: field population＜Bangladesh.(2) Detoxification enzyme activity of different BPH population induced withinsecticide was determined indicated that: after BPH induced with imidacioprid, ESTand GST activity of field population overall were on the rise, but there are fluctuations,EST and GST activity of Bangladesh were on the rise, but there are fluctuations: ESTactivity of biotypeâ…¡significantly decline, and GST activity were on the rise, but thereare a certain fluctuation: MFO activity of all population were on the rise. So that ESTand GST activity is not major factor of different populations of BPH to imidaclopridmetabolic resistance, and MFO had high correlation with the metabolic resistance toimidacloprid. After BPH induced with malathion, EST activity of field population andbiotype Bangladesh were on the rise, there was no fluctuation: and GST activity hadrisen, but the overall difference was not significant: and MFO had some risen,difference was significant in every generation. So that EST was closely related withmalathion metabolism resistance, GST was not related with malathion metabolismresistance, and MFO also plays some roles in the resistance development. The resultsalso showed that different populations, different gender and different phase in thedevelopment of BPH of various detoxification activity had significantly different.(3) Virulence of biotypeâ…¡and biotype Bangladesh were determined after resistantvarieties rearing, the results indicated that virulence of every generation hadsignificantly differences in identify varieties. The biotypeâ…¡rearing on IR36 for 4generations, virulence of 3rd generation to IR26 was 5.4 grades, virulence of 1st and 4tgeneration to Mudgo were 4.0 and 4.5 grades, which were less than 5.9 grades, theyare from susceptibility to resistance, virulence of 3rd and 4th generation to IR36 were6.9 and 6.0 grades, which were more than 5.9 grades, they are from resistance tosusceptibility. The biotype Bangladesh rearing on RHT for 4 generations, virulence of4th to IR26 was 5.7 grades, virulence of 1st generation to Mudgo were 5.1 grades,virulence of 4th generation to IR36 were 4.6 grades, virulence of 1st and 4th generation toASD7 were 4.0 and 4.8 grades, which were less than 5.9 grades, they are fromsusceptibility to resistance, that shows virulent shifts constantly when different biological adapt to resistant varieties.(4) Detoxification enzyme activity of BPH was determined after different biotyperearing on resistant varieties, detoxification enzyme activity of different gender anddifferent developmental stages had significantly difference. RHT has a certain choice tohigh-EST individuals of Bangladesh and IR36 has a certain choice to low-ESTindividuals of biotypeâ…¡. IR36 and RHT were able to induce GST activity of biotypeâ…¡and biotype Bangladesh male, female and the nymphs to rise respectively, IR36 caninduce MFO activity of biotypeâ…¡male and female to rise and MFO activity ofnymphs had a little change: RHT has a certain choice to low-MFO individuals ofBangladesh.