Evaluation Of The Inheritance And Stability Of Cyflumetofen Resistance In Tetranychus Cinnabarinus (Boisduval)

The carmine spider mite,Tetranychus cinnabarinus?Boisduval?,is an important agriculture pest,which could feed on more than hundred crops including cowpea,eggplant and so on.T.cinnabarinus has strong fecundity,short generation cycle,small range of activity.In the past decades,with indiscriminate use of pesticide,the resistance of this mite has become a growing problem.As a new acaricide,cyflumetofen can effectively control spider mites and it was safe to non-targeted organisms,so it could be a main acaricide in future.In this study a cyflumetofen resistance strain was selected in T.cinnabarinus under laboratory condition,and the mode of inheritance,fitness and stability in this strain and the resistance risk of cyflumetofen were evaluated.Our result offers a theoretical basis for scientific use of this new acaricide.The results are as follows:1.A cyflumetofen-resistant strain?Cy R?was selected for 97 generations from the relatively susceptible strain?SS?and developed 26.85-fold resistance.The LC50 increased to 58.80mg/L from 2.19mg/L.2.Reciprocal crosses showed that the degree of dominance were-0.24 and-0.32 respectively,indicated the resistance to cyflumetofen was inherited as an incomplete recessive trait.Backcrosses revealed the resistance of cyflumetofen was controlled by more than one gene according to the fact that different log concentration-probit line between expected and observational.3.Life tables of Cy R and SS were recorded,low fecundity and livability were found in Cy R which suggested a fitness cost in it.The relative fitness also supported the same result?Rf=0.88<1?.4.A substrain?Cy R_D?was separated from Cy R₈5 to explore the resistance stability without cyflumetofen stress.In terms of susceptibility to cyflumetofen,the resistance ratio of Cy R_D decreased to 5.2-fold from 21.6-fold after 5 generations and decreased to 3.8-fold after 12 generations.The activity of detoxifying enzymes?GSTs,MFO and Car E?were significantly increased in Cy R₈5,but the activity of these enzymes would significantly decrease in Cy R_D without cyflumetofen stress.Ten resistance related genes?TCGST-M2?TCGST-M3?TCGST-M4,TCCar E-4?TCCar E-14?TCCar E-12?TCCar E-23,CYP389C11?CYP392D6?CCYP385C2?of detoxifying enzymes were identified through high-throughput sequencing and q PCR.Eight of them were up-regulated and two down-regulated in Cy R.Futher more,the expression of these eight up-regulated genes would significant decreased in Cy R_D12 and two down-regulated genes would significant increased in Cy R_D12.The results of toxicity,biochemistry and basal molecular biology all indicated that the resistance to cyflumetofen in T.cinnabarinus was not stable without cyflumetofen stress.5.A low?h2=0.005?realized heritability after 97 generations' selection with cyflumetofen indicated a slower pace in developing resistance.Bioassay revealed that there was no cross-resistance between cyflumetofen and other four acaricides including avermectin,fenpropathrin,propargite and bifenazate,but the cross-resistance to pyridaben reached a high level?63.78-fold?,which meant the cyflumetofen and pyridaben should not be mixed or rotated used in the fields.In conclusion,a medium resistance strain of T.cinnabarinus was selected with cyflumetofen in laboratory.fitness cost were found in Cy R,and its resistance was unstable.Results of crossing and backcrossing studies suggested the inheritance of cyflumetofen resistance was incomplete recessive and controlled by more than one gene.All together,the resistance risk of cyflumetofen in T.cinnabarinus was low.