Study On Genetic Structure Of Eriosoma Lanigerum In Shaanxi And Influence Of Main Ecological Factors On Its Population Dynamics

Study in genetic structure and population dynamics of pests can find reasons of their evolution,gene flow and population explosion,providing theoretical basis for integrated pest management.In our research,Eriosoma lanigerum(Hausmann)(Hemiptera: Aphididae)was selected as the object which is a major pest in apple production.Firstly we collected samples of 29 populations from Shaanxi and 2 populations from Shandong and Gansu Province in China,and researched genetic structure of E.lanigerum on 6 microsatllite loci.Then we used the age-stage group life table to study parameters in growth and fecundity of E.lanigerum in order to analyse effects of temperature on population dynamics.Finally,we investigated 2 years population dynamics of E.lanigerum on the entire tree and different parts to analyse spatial population variation of E.lanigerum.Population of natural enemies(Harmonia axyridis and Aphelinus mali)were also included in the investigation to research inhibitory effect on population of E.lanigerum.We put stick belt on the trunk of trees to restrict the movement of E.lanigerum and analyse the effect of habitat on population dynamics.The main conclusions are as follows:1.Genetic structure analyses by using microsatellite markers indicated:(1)The 6microsatellite loci of E.lanigerum had high level of deviation from Hardy-Weinberg equilibrium,excess heterozygosity and significant linkage disequilibrium.(2)The 31 populations of E.lanigerum also deviated from Hardy-Weinberg equilibrium significantly and the heterozygosity excess except for XYCW in Erio3,TCYT in Erio33,XYLQ,WNCC in Erio75,XYLQ,XYQX in Erio78.Because most populations had insignificant genetic differentiation except for WNHC,WNCC,TCYT,TCYJ,YALC,YAYIC and YAHL,it was inferred that E.lanigerum has experienced a bottleneck effect in China.And "super clone" occurd which can adapt to the environmental conditions of different regions.(3)The 31 populations were clustered into 3 groups.Clusters1 consisted of 16 populations,including XYYS and others.Clusters2 consisted of 8 populations,including XYLQ and others.Clusters3 consisted of 7 populations,including WNHC and others.The reasons for the genetic differences between groups are twofold.On the one hand,they may have different sources of population invasion.On the other hand,different conditions selected population of E.lanigerum.2.Through researching age-stage group life table of E.lanigerum at different temperatures(19℃、22℃、25℃、28℃and 31℃),it was found that:(1)E.lanigerum has a trend of occurrence at 19℃,22℃and 25℃.At 25℃,the intrinsic rate of increase,net reproductive rate and mean generation time of E.lanigerum were significantly higher than those at other temperatures.(2)At 28℃ the population of E.lanigerum showed an increasing trend but was lower than 19℃,22℃and 25℃.(3)At 31℃ the survival rate and net reproductive rate were extremely low and the population reduced.In summary 25℃ is the optimal temperature for E.lanigerum.High temperatures above 31℃ can reduce the population of E.lanigerum.3.Study on population of E.lanigerum and its enemy indicated:(1)It was found that there is one peak of E.lanigerum population,starting at mid to late May throughout the year.During this period E.lanigerum was mainly distributed on the side branches of trees.Under the same effective accumulated temperature throughout the year the population size of E.lanigerum varied greatly among different years.(2)There was a significant lag effect between the parasitism rate of Aphelinus mali and the population size of E.lanigerum.Harmonia axyridis migrated into the orchard from wheat fields and occured sporadically throughout the year with a small number.So,the control function of natural enemies of E.lanigerum is insignificant during peak.(3)Restricting movement could inhibit population size and spread of E.lanigerum during peak significantly.In summary,it was demonstrated that genetic differentiation among 24 populations of E.lanigerum was low."Super clone" of E.lanigerum occured so as to bloom in most regions in China.25℃ was the crucial temperature increasing population size of E.lanigerum.From mid to late May to late July was the crucial time increasing population size of E.lanigerum.Lateral branches was the crucial position of the tree increasing population size of E.lanigerum.Natural enemies’ control function in population of E.lanigerum was insignificant in early stage.Restricting movement can be an effective method for inhibiting population size of E.lanigerum.This study provided a theoretical basis for genetics,ecology study and control strategies of E.lanigerum.