Genetic Divergence And Control Strategy Of The Peach Fruit Moth Carposina Sasakii Matsumura

The peach fruit moth Carposina sasakii Matsumura(Lepidoptera: Carposinidae)is a serious pest,the larvae of which bore into the fruit,causing great economic losses.C.sasakii is widely distributed in East Asia,feeding on more than 10 species of fruits.However,it is unclear yet whether genetic divergence occurs among the various host plants.In this thesis,the whole mitochondrial genome was sequenced to investigate the genetic differentiation of C.sasakii among host plants for the first time,with Carposina coreana Kim as the outgroup.Besides,the bored fruits were collected from various hosts and reared in the laboratory to confirm the voltinism of C.sasakii in the Guanzhong region of Shaanxi Province based on the cocoon types.Based on the research results,we proposed the strategies for population control of C.sasakii.The main results were as follows:In this study,specimens of C.sasakii were collected from five host plants including apricot,peach,apple,wild jujube and hawthorn in Lintong District,Xi’an City,Shaanxi Province,and specimens of C.coreana were collected in Danfeng County,Shaanxi Province.After comparing and analyzing the mitochondrial genomes of C.sasakii on different hosts,a phylogenetic tree was constructed using Bayesian Inferrence and Maximum Likelihood method.The phylogenetic tree showed that there was no significant genetic differentiation between different lineages,and the genetic distance showed that the mitochondrial genomes of these host lineages had little genetic difference.We detected the number of mitochondrial gene variation sites in C.sasakii,with the cox1 gene having the highest variation.The gene cox1 of C.sasakii is the most variable site in the mitochondrial gene.The phylogenetic tree constructed by cox1 gene does not support that host species differentiation occurs in C.sasakii.We conducted a statistical survey on the cocoon types of C.sasakii on these five hosts.It was found that all the C.sasakii had spherical cocoons diapause in the same year no matter the host is apricot,wild jujube or hawthorn,and only one generation occurred in one year.The collected long cocoons were identified as Grapholita molesta,rather than C.sasakii.C.sasakii on other hosts produces two types of cocoons,some of which pupate to develop for the second generation.In combination with the dynamics of adult occurrence,we predicted that the peach fruit moth could only complete 1 or 2 generations per year in Guanzhong Rgeion of Shaanxi Province.Combined with mitochondrial and biological data,we found the life cycle of C.sasakii is highly compatible with the host occurrence period,indicating that C.sasakii on different hosts is likely undergoing seasonal species speciation,but the differentiation period is not long enough.The mitochondrial genome is relatively slower in evolutionary rate and the difference is not significant,so that it is not suitable to be used to detect the intraspecific speciation in C.sasakii.Therefore,the mitochondrial genome,as a molecular marker,has great limitations in the study of C.sasakii interspecific differentiation adapted to agricultural production.Finally,we proposed the strategies for population control of C.sasakii on different hosts and their occurrence.In the planting area of single planting apricot or hawthorn in Guanzhong region,C.sasakii only occurred one generation a year.The orchard should be cleaned in time in winter and spring every year to destroy the overwintering cocoons.In areas where a variety of fruit trees are planted,the C.sasakii will be transferred to the host.Attention should be paid to the migration and fruit development of C.sasakii in other local fruit trees,so as to reduce the number of adults in the orchard and prevent the damage of the host.