| As the ryanodine receptor activator, chlorantraniliprole is efficient to lepidopteran pest,the channel of insect RyR remains open after acted by chlorantraniliprole, which caused theconcentration of calcium ions increased in cell. Sustained release of ions will result in the pestcontinue to shrink, vomiting, defecation, and then food refusal eventually leading to death.With a large number of chlorantraniliprole used in the control of the pest population, theproblem of resistance of pest has become increasingly prominent. In this paper, based on theharm of cruciferous vegetables diamondback moth (Plutella xylostella L.) as the researchobject, we research the biological activity of chlorantraniliprole to diamondback moth,resistance selection, the relative biological fitness of resistant population, resistance riskassessment and the resistance molecular mechanism; what’s more, taking the emamectinbenzoate as the control, we discuss the law of development of diamondback moth to differentinsecticide. We hope to provide a scientific basis of comprehensive management strategy forfacing such novel pesticide. The main results are as follows:1. The toxicity of chlorantraniliprole against three population of the3rd larvae ofdiamondback moth was tested by topical application, the results suggested the72h LD50ofchlorantraniliprole to relative susceptive strain was0.870μg/g, the72h LD50to filedpopulation, BY and ZC, was17.604μg/g and1953.925μg/g, respectively.; The72h LD50ofemamectin benzoate to diamondback moth was21.862μg/g.2. The3rd larvae of susceptive diamondback moth was selected by chlorantraniliprole to18generations, the LD50was45.67μg/g, developed52.51-fold resistance, the resistancedeveloped slowly from F0to F8, and rapidly after F9, moderate levels of resistance to F18hadbecome; the BY population was selected to6generations by chlorantraniliprole, its LD50was26.95μg/g and30.98-fold resistance ratio; The resistance ratio of3rd larvae of susceptivediamondback moth to emamectin benzoate after selected for14generations was14.28, andthe value of LD50was312.20μg/g.3. Relative fitness experiments for the strains of susceptive and resistant of diamondbackmoth showed that the fitness of resistant strain was0.55. Compared with that in susceptiblestrain, eggs and pupae of resistant strains were extended, larval period increased, adult longevity was shorten, decline in fecundity; the rate of emergence, larval survival andpupation rate of resistant were reduced.4. Realized heritability (h2) of resistance in different selection stages was evaluated basedon the Tabashnik’s methods, the results showed that realized heritability for the entire18generations selection experiment was0.258. Assuming the selection pressure ofchlorantraniliprole to diamondback moth was50%、60%、70%、80%、90%and99%,respectively, assume the slope was2.0, δp=0.5, predicting the generations of Plutellaxylostella to obtain10-fold resistance to chlorantraniliprole: When h2=0.26, it required4~10generations to obtain10-fold increase in the LD50under selection pressure at50%~90%;When h2=0.13, it required9~19generations.5. We have cloned and characterized about4400bp sequence of PxRyR COOH-terminalof S, BY, F18and ZC, which contains most of functional domains of RyR, the result ofsequence alignment suggested that the announced mutation point, which was closely relatedto the resistance development of diamondback moth to chlorantraniliprole, was found in thefiled population of BY and ZC, in addition to a deletion of14amino acids in this part presentin all the resistant population.6. Real-time quantitative PCR was used to determine the mRNA expression level of RyRin the four strain/population, the expression levels of PxRyR in BY, F18and ZC wasrespective0.72,0.45, and0.49times than that in S strain, indicting that the down-regulationexpression of receptor was related to the resistance. |
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