| The freshwater pearl mussel Hyriopsis cumingii is a freshwaterbivalve widely distributed in China and is the most commerciallyimportant freshwater pearl mussel species in our country. The traditionalmethods of genetic improvement of quantitative traits have relied mainlyon phenotype and pedigree information, which are easily influenced byenvironmental factors. Compared with traditional breeding methods, themolecular marker-assisted breeding is not susceptible to environmentalimpacts. Also, it can enhance breeding efficiency and shorten thebreeding cycle. In this study, we have isolated lots of microsatellite DNAmarkers by Magnetic beads enriched method. Then the isolatedmicrosatellite DNA markers were used to construct the genetic linkagemap for Hyriopsis cumingii and localized some pearl production traits inthe Hyriopsis cumingii by composite interval mapping. Mainly includedthe following contents:1. Two microsatellite-enriched library of the Hyriopsis cumingii wasconstructed using magnetic beads enriched method with biotin-labeledoligo(GA)10and (CA)10. One thousand nine hundred and seventy pairs of primers were designed according to these sequences with softwarePrimerSelect and synthesized. Seventeen loci in43tetranucleotide repeatmicrosatellites showed high levels in genetic polymorphism testing on36individuals sampled from Dongting Lake. The number of alleles at eachlocus ranged from6to28. The expected and observed heterozygositiesvaried from0.6776to0.9464and from0.6389to1.000, respectively. ThePIC value ranged from0.630to0.929. Twelve microsatellite loci fitted toHardy–Weinberg equilibrium. Compared with the previous dinucleotiderepeat microsatellite developed in our laboratory, these17tetranucleotiderepeat microsatellite loci showed higher polymorphism. Also, these17microsatellite loci can do genotyping easier by conventional methodssuch as polyacrylamide gel electrophoresis and cost savings. Therefore, itoffered accurate and inexpensive microsatellite markers for populationgenetic analysis and paternity test in Hyriopsis cumingii.2. The genetic linkage maps of Hyriopsis cumingii were constructedwith509microsatellite markers. The male map was composed of436markers in19linkage groups, covering1745.9cM with an averageinterval of4.19cM. The female map consisted of425markers in19linkage groups, spanning2078.8with an average interval of5.13cM. Theobserved coverage was90.08%in female map and91.40%in male map.The integrated map consisted of508markers in19linkage groups,spanning1940.3cM with an average interval of3.97cM. The coverage of the integrated linkage map was92.59%. Meanwhile, we constructed thelinkage map of Hyriopsis cumingii directly with509microsatellitemarkers. For this map,506markers were assigned in19groups, with anaverage interval of3.94cM. The total length of this map was1922.3cMand the coverage of this map was92.56%.3. The locations and effects of quantitative trait loci (QTL) wereestimated for sixteen growth-related and shell color related characters inHyriopsis cumingii based on the genetic maps. Twenty-nine putativelysignificant QTL were detected for sixteen characters, including2for shelllength,2for shell height,2for shell width,2for total weight,3for shellweight,3for outer pallium weight,3for inner pallium weight and12forshell color. These QTL were mainly on LG1, LG2, LG3, LG4, LG6, LG8,LG9, LG14, LG17and LG18. The phenotypic variation explained by theQTLs ranged from15.1%to45.8%. Four QTLs were associated withshell color on the linkage of LG17GW(P<0.01), explaining26.0%to28.9%of the trait variation. These QTLs for growth-related and shellcolor related characters clustered on the10linkage groups, which meansthese growth-related and shell color related characters shared thecommon genetic elements. The construction of Genetic linkage map ofHyriopsis cumingii and the QTLs for growth-related and shell colorrelated characters can be used in marker-assisted selection of Hyriopsiscumingii and lay a foundation for cloning resistance genes. |
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