鲤饲料转化率性状的QTL定位及遗传效应分析

数量性状(QTL)定位是实现分子标记辅助育种、基因选择和定位、培育新品种及加快性状遗传研究进展的重要手段。饲料转化率是鲤鱼的重要经济性状和遗传改良的主要目标,而通过QTL定位获得与饲料转化率性状紧密连锁的分子标记以及相关基因是遗传育种的重要工具。研究利用SNP、SSR、EST-SSR等分子标记构建鲤鱼(Cyprinus carpio L.)遗传连锁图谱并对重要经济性状进行QTL定位。选用174个SSR标记、41个EST-SSR标记、345个SNP标记对德国镜鲤F2代群体68个个体进行基因型检测,用JoinMap4.0软件包构建鲤鱼遗传连锁图谱。再用MapQTL5.0的区间作图法(Interval mapping,IM)和多QTL区间定位法(MQMMapping,MQM)对饲料转化率性状进行QTL区间检测,通过置换实验(1000次重复)确定连锁群显著性水平阈值。结果显示,在对饲料转化率性状的多QTL区间定位中,共检测到15个QTLs区间,分布在9个连锁群上,解释表型变异范围为17.70%—52.20%,解释表型变异最大的QTLs区间在第48连锁群上,为52.20%。HLJE314-SNP0919(LG25)区间标记覆盖的图距最小,为0.164 cM;最大的是HLJ1439-HLJ1438(LG39)区间,覆盖图距为24.922 cM。其中区间HLJ1439-HLJ1438、HLJ922-SNP0711解释表型变异均超过50.00%,可能是影响饲料转化率性状的主效QTLs区间。与饲料转化率相关的15个QTLs的加性效应方向并不一致,有3个区间具有负向加性效应,平均为0.027;12个正向加性效应,平均值为0.06。研究检测出的与鲤鱼饲料转化率性状相关的QTL位点可为鲤鱼分子标记辅助育种和更进一步的QTL精细定位打下基础。

MAPPING AND GENETIC EFFECT ANALYSIS ON QUANTITATIVE TRAIT LOCI RELATED TO FEED CONVERSION RATIO OF COMMON CARP(CYPRINUS CARPIO L.)

The common carp(Cyprinus carpio L.),one of the most important species for aquaculture in China,is a widespread freshwater fish of eutrophic waters in lakes and large rivers.The wild populations are considered vulnerable to extinction,but the species has also been domesticated and introduced into environments worldwide,and is often considered as an invasive species.However,genetic degeneration,such as low growth rate,small body size,weak disease-resistance,etc.,emerged in common carp with the rapid development of its farming scale.Quantitative traits(for example,the feed conversion ratio of common carp) refer to phenotypes that vary in degree and can be attributed to polygenic effects,i.e.,product of two or more genes,and their environment.Quantitative trait loci(QTLs) are stretches of DNA containing or linked to the genes that underlie a quantitative trait.Mapping regions of the genome that contain genes involved in specifying a quantitative trait is done using molecular tags such as SSR,EST or more commonly SNPs.This is an early step in identifying and sequencing the actual genes underlying trait variation.Researches of genetic diversity,kin discrimination,strain identification,genetic linkage map construction,trait-related marker screening,genetic evaluation and QTL are the effective way to solve these problems of breeding in common carp.In this paper,a group of F2 hybrids German mirror carp including 68 individuals was used to construct a linkage map by using 560 markers(174 SSR markers,41EST-SSR markers and 345 SNP markers).Quantitative traits loci(QTLs) associated with feed conversion ratio were identified by interval mapping and MQM mapping of the software MapQTL5.0.A linkage group wide permutation test(1000 replicates) determined the significance of the maximum LOD value over the various intervals analyzed for each linkage group.The results indicated that fifteen QTLs were identified for feed conversion ratio on nine linkage groups,which explained 17.70% and 52.20% of the total variation of feed conversion ratio,respectively.Two QTLs were associated with LG25(HLJE314-SNP0919) and LG39(HLJ1439-HLJ1438),which covered the lest 0.614 and most 24.922.There were two QTLs(HLJ1439-HLJ1438 and HLJ922-SNP0711),which explained over 50.00% of the total variation of the feed conversion ratio.They were major QTLs associated to the feed conversion of common carp.Three QTLs were negative additive effect with the average value of 0.027,while the others positive additive effect with the average value of 0.06.The results also suggested that the feed conversion ratio traits should be determined by more than one loci which was conformed to the theory on quantitative genetics.This work investigated the correlation between markers and growth traits in common carp and obtained trait-related QTL and the results would be valuable for marker-assisted breeding in common carp.