Resistance Risk Assessment And Metabolic Resistance Mechanism Exploration Of Laodelphax Striatellus（Fallén） To Cyantraniliprole

The research on the risk and mechanism of resistance before resistance development is helpful to the scientific application of pesticides in the field and to delay the emergence and development of insecticide resistance.Laodelphax striatellus（Fallén）is an important pest that harms many graminaceous crops including rice,corn and wheat,and easy to cause serious economic losses.The L.striatellus was controlled mainly by using different chemical insecticides in field,and have developed different resitance levels to different insecticides.Cyantraniliprole is a diamide insecticide with unique mechanism of action,which has been registered for the control of L.striatellus.In this study,the cyantraniliprole-resistant strain（CyR）was obtained by continuous selection using cyantraniliprole in laboratory.The resistance risk was comprehensivly assessed according the resistance development rate,actual heritability,resistance stability,biological fitness,and cross resistance,respectively.The metabolic resistance mechanism of L.striatellus to cyantraniliprole was preliminarily explored by comparing the activities of three metabolic enzymes and the expression of some detoxification metabolic genes in CyR and SS strains.The main results of this study are as follows:The CyR strain with the middle resistance level was obtained after 25 generations of continuous selection in laboratory.Compare with SS strain,the LC₅₀value increased from 14.50mg·L^-1 to 248.54 mg·L^-1,showed a 17.14 times of resistance ratio.From F₀ to F₁₆ generation,the resistance developed slowly,and the resistance ratio only 3.63 times,showed no resistance.After F₁₆ generation,the development of resistance developed rapidly,and the resistance ratio increased 13 times after 9 generations.The realized heritability of CyR strain was 0.0751.The resistance ratio increased to 10-fold only need 12 generations if the selected pressure reached to 90%mortality in each generation.The results of resistance stability showed that the LC₅₀ value of the CyR strain decreased from 190.69 mg·L^-1 to 140.35 mg·L^-1 after five generations of continuous feeding without any insecticides,and the resistance ratio decreased 3.47 times with a decreased rate of 0.0266 per generation.The biological fitness of CyR strain was 1.01,showed no fitness costs.Compared with SS strain,the 2^nd,3^rd and 4^th instars,nymphal duration,the total preoviposition period and the mean generation time of CyR strain were significantly reduced.However,there were no significant differences in adult longevity,fecundity,emergence rate,female ratio,hatchability,intrinsic rate of increase,finite rate of increase and net reproductive rate between SS and CyR strains.The result of the cross-resistance showed that the CyR strain had no cross-resistance to the tested nine insecticides（triflumezopyrim,pymetrozine,flonicamid,flonicamid,dinotefuran,clothianidin,thiamethoxam,nitenpyram,and imidacloprid）.The synergistic test results showed that both TPP and PBO showed a certain synergistic effect on CyR and SS strains,and the synergistic effect was more obvious in the CyR strain.The results of three detoxification enzyme activities showed that the activities of P450s and CarE were significantly higher in CyR strain than in SS strain,which were 1.69 and 1.30 times compared with SS strain,respectively.However,the GST activity had no differences in two strains.The results of some metabolic genes expression showed that the expression level of CYP419A1v2 in CyR strain was 6.10 times higher than that in SS strain,showed the highst up-regulation.The CarE gene LsCarE5 also showed obviously up-regulated in CyR strain,exhibit1.94 times level with SS strain.In conclusion,the increased activities of corresponding metabolic enzymes caused by overexpression of P450s and CarE genes may play a major role in the metabolic resistance of L.striatellus to cyantraniliprole.