川渝稻区水稻螟虫种类组成及大螟不同地理种群遗传多态性的差异分析

Genetic diversity of different geographical populations of rice stem borers,Sesamia inferens,in the Sichuan-Chongqing rice region

【目的】通过对川渝稻区水稻孕穗灌浆期螟虫种类组成情况及大螟Sesamia inferens不同地理种群的遗传结构的分析,了解各地区水稻孕穗灌浆期螟虫发生情况及大螟种群间的亲缘关系,为水稻螟虫的区域治理对策提供新的依据。【方法】对川渝地区13个市县的水稻螟虫发生情况进行调查及采样,利用MEGA等软件对采集到的大螟样本的线粒体COⅠ基因和COⅡ基因序列进行分析,并构建分子系统发育树,以获取样本群体遗传多样性信息。【结果】川渝稻区水稻孕穗灌浆期螟虫主要由二化螟Chilo suppressalis、三化螟Tryporyza incertulas和大螟组成,二化螟为优势种群,其次为大螟;而不同地区间螟虫种类和优势度存在差异,其中川西稻区只有二化螟,重庆地区有二化螟和大螟。大螟不同地理种群的遗传多样性分析结果表明,大螟幼虫线粒体COⅠ基因序列在627bp区段中共有386个多态性位点,包含16个单倍型;川东地区大螟种群的单倍型多样度为0.91057;系统发育树显示,川东地区(除营山)大螟地理种群聚合为一大分支,其他大螟地理种群聚合为一个大分支。而对同批大螟线粒体COⅡ基因序列分析结果表明,在363 bp的区段中存在228个位点多态性,有10个单倍型;川东地区大化螟种群的单倍型多样度为0.71579;在系统发育树中,重庆地区种群、杭州地理种群和梓潼种群聚合为一支,其余种群聚合为一支。【结论】川渝稻区螟虫主要由二化螟、三化螟和大螟组成,二化螟为优势种群,其次为大螟。川东地区大螟线粒体COⅠ和COⅡ基因多态性比其他地区丰富。川渝稻区大螟不同地理种群间的遗传分化距离不明显,地理种群之间的遗传分化与分布之间的相关性不大。

[Objectives]To investigate the relative abundance of different species of rice stem borers and the genetic diversity of different geographical populations of the pink stem borer,Sesamia inferens(Walker)in rice growing regions of Sichuan-Chongqing,and provide suggestions for the regional management of borer populations.[Methods]We conducted a field survey during the rice grain-filling stage to determine the relative abundance of different species of rice stem borers in 13 cities in the Sichuan-Chongqing rice growing region and collected S.inferens specimens from 13 geographical populations for genetic analysis.We then sequenced the cytochrome oxidase subunitⅠ(COⅠ)and cytochrome oxidase subunitⅡ(COⅡ)of mitochondrial DNA(mtDNA)of S.inferens specimens from different populations and analyzed their genetic diversity sequence varication with MEGA and DNA Sequence Polymorphism.[Results]The species of rice stem borer identified in our survey were Chilo suppressalis,Tryporyza incertulas and S.inferens,and the dominant species were C.suppressalis and S.inferens.A 627 bp segment of COⅠgene from 60 mature S.inferens larvae was sequenced and analyzed,resulting in the identification of 386 variable sites and 16 haplotypes.Haplotype diversity among different populations in eastern Sichuan was 0.91057.A phylogenetic tree indicates that,with the exception of the YS population,all other populations from eastern Sichuan grouped into one great clade and all other geographic populations grouped into another great clade.Based on the same 60 DNA samples,the length of the COⅡgene was 363 bp,and 228 variable sites and 10 haplotypes were identified.Haplotype diversity among different eastern Sichuan populations was 0.71579.A phylogenetic tree showed that the Chongqing city population,Hangzhou population and ZY population grouped into one clade,whereas all other geographic populations grouped into another clade.[Conclusion]The dominant species of rice stem borer in the Sichuan-Chongqing rice growing region are C.suppressalis and S.inferens.Haplotype diversity based on both COⅠand COⅡsequences indicates that there is more haplotype diversity in eastern Sichuan than in other geographical areas.We found little correlation between genetic diversity and geographical populations.