Population Dynamics Analysis Of Plutella Xylostella Based On DYMEX Model And Functional Analysis Of P-glycoprotein

The diamondback moth,Plutella xylostella?L.?,is a worldwide pest that mainly damanges cruciferous crops.Since the 1980s,Abamectin causes a high level of resistance due to its large use for agricultural pest control?including Plutella xylostella?.The P.xylostella has possesed the characteristics of migration.Although a large number of studies have described its resistance status and partial resistance mechanisms in the northern China,there are few studies on the persistence of population dynamics.In this study,long-term population monitoring of the P.xylostella was conducted using pheromones in four regions of northern China?Changping and Haidian,Xuanhua and Zhangbei?.Field research has provided insights into the field practice of cruciferous vegetable planting in the above regions.The field management of cruciferous vegetables in the four regions was measured through field surveys.The DYMEX model was implemented to study seasonal phenology,population trend abundance of the trapping data and field planting patterns.The aim is to clarify the source and relevant influencing factors of the P.xylostella population in the northern China.In order to further clarify the resistance mechanism of P.xylostella to abamectin.RNA interference technology was used to study the role of P-glycoprotein?Pgp?gene in abamectin resistance in P.xylostella based on previous studies.The objective of this study to elucidate the resistance mechanism of P.xylostella to abamectin and delay the service life of abamectin.Sex pheromone trap technology was used to continuously monitor the population dynamics of P.xylostella from Haidian and Changping in Hebei?2009-2015?,Xuanhua and Zhangbei?2009-2014?in Beijing.The results showed that the mean time from the first to the last trapping within a year was 204 d in Haidian,202 d in Changping,170 d in Xuanhua and 146 d in Zhangbei.Peak numbers occurred in late-May to mid-June in Haidian,mid-June to early July in Changping and mainly concentrated in the May-June period in Xuanhua and Zhangbei.There was a large“outbreak”in 2009 in all locations,with the annual total number of moths caught in four traps reaching 8823?Changping?,14664?Haidian?,14370?Xuanhua?and 27648?Zhangbei?.The number remained at a relatively constant lower level in the lowest year in 2014 with 1568?Changping?,3379?Haidian?,1652?Xuanhua?and 1432?Zhangbei?moths caught in each location over the season.In general,the spring is serious and the fall is light.The model captures phenology and the general trends in abundance are analyzed base on the DYMEX.The results are shown the climate is more suitable for P.xylostella in Changping and Haidian in 2010,2012 and 2015;Xuanhua in 2011 and 2013;Zhangbei in 2013.Regressions of ln predicted on ln observed numbers were significant for 18 out of 25 site and year comparisons.Threshold spray prediction results were showing threshold sprays varied between 1 and 5 applications.In general threshold spraying generated better agreement with the observed?13 significant regression compared to 10?.The resistance ratio of P.xylostella to abamectin was about 73-fold through continuous selection.The 3rd instar larvae of P.xylostella were injected with dsRNA using microinjection technique.The results showed that the expression level of PxPgp1gene was decreased at 36 h,was the lowest at 48 h and recovered after 72 h through microinjection.The gene expression levels decreased by 42.45%,53.63%,and 27.60%,respectively,relative to the control group.The sensitivity of P.xylostella to avermectin was determined at 24 h,48 h,and 72 h after microinjection(The assay concentrations were LC₂₀=0.768?g/mL and LC₅₀=2.724?g/mL).The results showed that the mortality rate of the LC₂₀ concentration in the treatment group was 24 h=23.4%,48 h=36.70%and 72 h=15%,and the control group mortality was 24 h=5%,48 h=12.5%and 72h=12.5%.But the mortality rate for LC₅₀ concentration in the treatment group was 24h=17.5%?48 h=62.5%and 72 h=17.5%,and the control group mortality was 24h=12.5%?48 h=35%and 72 h=7.5%.The sensitivity to abamectin we found that larval mortality experimental group higher than the control group after RNAi.It shows that PxPgp1 gene is associated with avermectin resistance in P.xylostella.