| Thrips palmi Karny(Thripidae:Thrips)is a crucial pest in agricultural and forestry production,causing damages to many plants.It was originated from South Asia and have now spread to Japan,Korea,Australia and most areas of China.Population genetic variation may lead to rapid adaptation and outbreak of T.palmi in new environment.Understand the genetic diversity and genetic structure of different populations will help to clarify the occurrence of T.palmi and improve control measures.In this study,we developed the first set of microsatellite markers for T.palmi,and we analyzed the genetic diversity and population genetic structure of T.palmi populations among different geographical populations and host-associated populations.We discussed the geographical,environmental,host plants and chemical control measures that may affect the population genetic variation of T.palmi.The results and conclusions were as follows:(1)Development of microsatellite markersIn this study,we developed novel microsatellite markers for T.palmi.First,we obtained randomly sequenced regions from the genome using next-generation sequencing and assembled 356 Mb genomic sequences.In total,104,229 microsatellites were identified from the genomic sequences,of which,64.02%were loci of dinucleotide repeat.Sixty primer pairs were initially validated in seven individuals.Twenty-six polymorphic markers were retained according to the amplification efficiency and polymorphism.These novel microsatellite markers developed in our study provide abundant molecular markers for the genetic study of T.palmi.(2)Genetic diversity of geographical populationsThe developed 26 microsatellite loci and mitochondrial cox1 gene were used to assess 14 geographical populations collected from China and one from Japan.The allele numbers ranged from 3 to 32,while the observed heterozygosity varied from 0.2803 to 0.6491.FIS ranged from-0.0769 to 0.1840.Allelic richness and private allelic richness varied from 1.91 to 6.48 and 0.09 to 0.97,respectively.Based on microsatellite loci and mitochondrial genes data,strong genetic differentiation was found among geographical populations representing distinct geographical regions.(3)Population genetic structure among geographical populationsIt was obvious that genetic differentiation in 14 geographical populations of T.palmi.in China,using mitochondrial coxl gene and microsatellite loci.The Fst was 0.01-0.21,and the differentiation between southern and other populations was the largest.All populations can be divided into 6 genetic clusters,including Japanese population,Hainan population,Yunnan population,Sichuan population,central and Eastern population,and Northern population.(4)Genetic diversity and population genetic structure among host-associated populationsMicrosatellite loci were used to assess genetic diversity and genetic structure of seven host-associated populations collected from Shandong Province.The allele numbers ranged from 3 to 27,the expected heterozygosity and observed heterozygosity varied from 0.4490 to 0.5684 and 0.4280 to 0.5701,respectively,while FIS ranged from-0.0022 to 0.0300.Based on mitochondrial genes data,SPLITSTREE analysis revealed 4 haplotypes in T.palmi.BAPS and STRUCTURE or DAPC analysis indicated that there is no host-associated genetic differentiation occurred.(5)Factors on shaping of the population genetic structureBased on microsatellite data,we analyzed the effects of geographical isolation,climatic factors,host plants and pesticide control on the genetic structure of T.palmi.Geographical distance and climate and environmental factors have great influence on the genetic structure of T.palmi,and resistance level also play a role.Host plants had no significant effect on population genetic differentiation. |
PDF Full Text Request