Identification Of Pest Species Boring Pinus Koraiensis And P.sylvestris Var.mongolica,and Genetic Diversity Research

Pinus koraiensis and P.sylvestris var.mongolica in northeast China are seriously harmed by pests,and a variety of borers appear together.This has a serious impact on the healthy growth of trees and the economic even ecological benefits of forest areas.In order to accurately identify the species of pests in the early stage of pest occurrence,the existing morphological identification characteristics of larvae were used to identify 1,117 samples from 11 collection sites in northeast China,and verified them by comparing COI gene sequences.On the basis of determining specific species,COI,ITS2 and EF-l? were used to conduct molecular phylogenetic analysis of different species,and to determine whether the genetic relationship of each taxon was different from that of traditional species division,and to provide scientific basis for it.Population genetic analysis was carried out on the main pests with wide distribution,and population historical dynamics and differentiation levels were judged based on genetic diversity and genetic structure,which provided theoretical basis for integrated pest control.The main research results are as follows:(1)Identification of pest species:According to the external morphological characteristics of the larvae and the COI gene sequence alignment,a total of 6 pests were identified.which were Dioryctria abietella,D.sylvestrella,Eupithecia abietaria debrunneata,Gravitarmata margarotana and two unknown species:Cydia sp.and a species of Pyralidoidea.It was found that the main pest of the cone was the D.abietella,and the main pest on the branch was the D.sylvestrella.The setal map provided in this study can be used as the identification tool for rapid identification in the pest control work.(2)Sequence composition and phylogenetic analysis:Sequencing of COI,ITS2 and EF-1?genes of four identified species showed that COI and EF-la genes of different species had the same sequence length,and ITS2 gene sequence length varied between species.Only the COI gene sequence showed obvious bias of A/T.The base substitution of COI and EF-1? gene mainly occurred at the third site of codon.Base substitution of ITS2 gene sequence is generally less,and sequence similarity within species is higher,and the differences among species are mainly due to long-term accumulation of insertion and deletion mutations.The range of genetic distance is obviously different under diff erent taxon,and the closer the relationship,the smaller the genetic distance.The phylogenetic tree constructed based on three genes has the same topological structure,each species can form a monophyletic group,and there is no deviation from the traditional species classification.(3)Population genetic structure of D.abietella:Haplotype mismatch distribution and the neutral test of COI and EF-1? gene sequences indicate that the population may have expanded recently.However,the variation of ITS2 gene conforms to the neutral evolution model and fails to show population expansion.The analysis of each geographical population shows that the bottleneck effect has appeared in all groups except the Sipeng(SP)population.The genetic differentiation between Qiqihaer(QQHE)population and many other populations is at a high level based on those three gene sequences.It is considered that the host plants and geographical isolation are the important factors that lead to the higher differentiation level.The genetic differentiation between Sipeng(SP)population and other populations only were showed based on the COI gene sequence.This is thought to be due to the fact that mitochondrial genes evolve faster than nuclear genes.The regression analysis of genetic distance and geographical distance showed that distance isolation had no significant effect on the genetic differentiation of 10 geographical populations.