| The polymorphisms of five candidate genes(IGFBP-3 gene, POU1F1 gene, 16SrRNA gene of mtDNA, intron I of GH gene,5′flanking region of Lf gene) and 7 microsatellite loci were analyzed by PCR-RFLP,PCR-SSCP and microsatellite DNA marker technique in five cattle populations(Qinchuan cattle, Luxi cattle, Jinnan cattle, Simmental F1 generation, Charollais F1 generation) and the effects of genotypes of five candidate genes and 7 microsatellite loci on slaghter traits(carcass depth, net meat weight, high quality meat weight,dressing percentage, net meat percentage, bone weight, rib eye area, daily gain, backfat thickness, carcass chest depth,carcass depth, ham girth, ham width, ham length, thigh meat thickness, loin meat thickness) were evaluated. The objects were to explore molecular markers of slaughter traits of five cattle populations, so that molecular genetic markers for efficient selection of carcass traits of beef cattle in China and construction of molecular genetic marker databases of Chinese beef cattle were provided primarily. The results were as follows: 1.The hereditary characteristics of five cattle populations 1.1 PCR-RFLP was applied to detect polymorphisms of three loci(IGBFBP-3 gene,POU1F1 gene,16S rRNA gene of mtDNA) in five cattle populations. (1)The result showed only two genotypes of AA and AB were at IGFBP-3 locus with no BB genotype in experimented cattle population. In Qinchuan cattle population, the frequencies of genotype AA /AB and allele A/B for IGFBP-3 gene locus were 0.729, 0.208/0.896, 0.104 respectively; In Luxi cattle population, their frequencies were 0.875, 0.125/0.938, 0.062 respectively; In Jinnan cattle population, their frequencies were 0.895, 0.105/0.948, 0.052 respectively. In Simmental F1 generation, their frequencies were 0.741, 0.259/0.875, 0.129 respectively; In Charollais F1 generation, their frequencies were 0.433, 0.567/0.717, 0.283 respectively. Distribuction of the genotype and allele frequency of this locus were closely in four cattle populations(Qinchuan cattle, Luxi cattle, Jinnan cattle, Simmental F1 generation) and genotype AA and allele A were dominant. Frequencies of genotype AA and AB were closely in Charollais F1 generation, but allele A was still dominant. This locus was at Hardy-Weinberg equilibrium(P>0.05). (2)Three genotypes of AA, BB and AB were detected at POUF1 loci, in five cattle populations. In Qinchuan cattle population, frequencies of genotype AA, BB and AB and allele A, B were 0.125, 0.708, 0.167/0.209, 0.791 respectively; In Luxi cattle population, theirs were 0.083, 0.375, 0.542/0.354, 0.646 respectively; In Jinnan cattle population, theirs were 0, 0.579, 0.421/0.211, 0.789 respectively; In Simmental F1 generation, theirs were 0.118, 0.444, 0.444/0.334, 0.666; In Charollais F1 generation, theirs were 0.167, 0.233, 0.600/0.467, 0.533. Distribution of frequencies of their genotype and allele were diverse in five populations. This locus was at Hardy-Weinberg equilibrium(P>0.05). (3)Mutation was detected for 16S rRNA gene locus of mtDNA in four cattle populations(Qinchuan catlle ,Luxi cattle, Simmental F1 generation, Charollais F1 generation). Mutation frequencies were 0.042, 0.042, 0, 0.037, 0.100 respectively. 1.2 PCR-SSCP was applied to detect polymorphisms in 5'flanking region of Lf gene and intron I of GH gene loci in five cattle populations. There were no polymorphisms in 5` flanking region of Lf gene and three genotypes of AA, BB and AB at GH intron I locus were found in five populations. (1)In Qinchuan cattle population, the frequencies of genotype AA, BB and AB and allele A, B were 0, 0, 1.00/0.500, 0.500. (2) In Luxi cattle population, theirs were 0.083, 0, 0.917/0.542, 0.458 respectively. (3)In Jinnan cattle population, theirs were 0, 0.632, 0.368/0.184, 0.816; In Simmental F1 generation, theirs were 0.037, 0.148, 0.815/0.444, 0.556 respectively. (4)In Charollais F1 generation, theirs were 0.617, 0, 0.767/0.617, 0.384 respectively. Outside Jinnan cattle, genotype AB was dominant. This locus was at Hardy-Weinberg equilibrium(P<0.05) in Jinnan cattle population. Other populations were at Hardy-Weinberg disequilibrium(P<0.05). 1.3 The genetic polymorphisms of five cattle populations were detected using the selected 7 microsatellite DNA markers. The CSSM66 showed one genetype in luxi cattle population.The abserved allelic number(Na) of 7 microsatellite loci were between 2~8 with effective allelic number (Ne) between 1.980~6.130 and heterozygosity(h) between 0.496 ~ 0.827 and polymorphism information content (PIC) between 0.375~0.974 in five populations. The Na, Ne, h and PIC of the same locus were diverse significantly in five cattle populations, which show their distinct hereditary characteristics. The PIC for most of microsatellite loci were above 0.9, higher than 0.5, so they were belonging to highlypolymorphic loci. This showed there were abundant heredity diversity in five cattle populations, which had more potential of charater selection for breeding than others.　　2. Relationship of PCR-RFLP polymorphisms and slaughter traits of five beef cattle populations The effects of genotypes of three candidate genes on slaughter traits were analyzed. The effects of genotypes of 16S rRNA gene locus of mtDNA on the traits were not statistically significantly in five populations. So were theirs of IGFBP-3 in Qinchuan cattle, Luxi cattle, Simmental F1 generation, Charollais F1 generation. (1)In Qinchuan cattle population, the effects of genotypes of POU1F1 were not statistically significantly on the 17 slaughter traits. (2)In Luxi cattle population, ham width of genotype BB at POU1F1 locus was higher than that of AB(P<0.05). (3)In Jinnan cattle population, the effects of genotypes of POU1F1 locus on the traits were not stastically significantly and ham width of genotype AA at IGFBP-3 locus was higher than that of AB(P<0.05). (4)In Simmental F1 generation, ham girth of BB at POU1F1 locus was higher than AB(P<0.05). (5)In Charollais F1 generation, genotypes of POU1F1 locus have significant effects on such traits as net meat weight, high quality beef weight, bone weight, daily gain, carcass chest depth and ham girth. Net meat weight of genotype AA was higher than genotype BB significantly(P<0.05). High quality beef weight of BB was lower than genotype AA and AB(P<0.05). Bone weight of genotype AA was higher than genotype BB and AB(P<0.05). Daily gain of genotype AA was higher than genotype BB and AB(P<0.05); Carcass chest depth of genotype AA was higher than genotype BB(P<0.05). Ham girth of genotype AA was higher than genotype BB and AB(P<0.05). 3. Relationship of PCR-SSCP polymorphisms and slaughter traits of five cattle populations The polymorphism of GH gene intron I were detected firstly in five cattle populations in this study and some polymorphisms were found in other four populations except Qinchuan cattle. The effects of genotypes of this locus on the carcass traits were analyzed. (1)In Luxi cattle, ham width and ham length of genotype AA were higher than genotype AB significantly(P<0.05). (2)In Jinnan cattle population, carcass chest depth of genotype BB was higher than genotype AB(P<0.05). (3)In Simmental F1 generation, daily gain of genotypes AA and BB were higher than genotype AB(P<0.05). (4) In Charollais F1 generation, carcass weight, net meat weight, high quality meat weight, bone weight and ham girth of AB were higher than genotype AA(p<0.05). 4. Relationship of microsatellite markers and slaughter traits of five cattle populations The effects of partial genotypes of 7 microsatellite loci(BM1824, INRA005, BM2113, ETH152, IDVGA27, HEL9, IDVGA3, CSSM66) on carcass traits were diverse in five cattlepopulations. The effects of genotypes of 2 microsatellite loci(HEL9, IDVGA27) on the all carcass traits were not statistically significant in five populations, and others'were significantly in this or that population. (1)In Qinchuan cattle population, genotype BC of BM1824 had significantly positive marking effect on rib eye area and daily gain (P<0.05) and genotype AB had significantly positive marking effect on ham girth(P<0.05). At INRA005, Genotype DE had positive marking effect on ham width(P<0.05) and genotype BE and DE had positive marking effect on loin meat thickness(P<0.05).(2)In Luxi cattle, genotype DE of ETH152 had significantly positive marking effect on net meat weight, net meat percentage, thigh meat thickness and loin meat thickness(P<0.05), and genotype BE and DE had significantly positive marking effect on carcass length(P<0.05). (3)In Jinnan cattle population, genotype CD of BM1824 had significantly positive marking effect on ham length(P<0.05). Genotype BC of ETH152 had significantly positive marking effect on daily gain(P<0.05). At INRA005, Genotype AB and CD had significantly positive marking effect on net meat percentage and genotype AB had positive marking effect on ham length(P<0.05). (4)In Simmental F1 generation, at CSSM66, genotype CD and EF had significantly positive marking effect on ham girth and ham length(P<0.05) and genotype CD had positive marking effect on ham width(P<0.05). Genotype CE of IDVGA3 had positive marking effect on loin meat thick(P<0.05). Genotype BE of INRA005 had positive marking effect on bone weight, ham width and ham length(P<0.05). (5)In Charollais F1 generation, at BM1824, genotype AB and CD had significantly positive marking effect on rib eye area and genotype AB had positive marking effect on carcass depth(P<0.05). Genotype EF of CSSM66 had significantly positive marking effect on carcass weight, net meat weight, bone weight and ham girth(P<0.05). Genotype FG of ETH152 had significantly positive marking effect on carcass depth, ham length, loin meat thickness(P<0.05). Genotype AB, CD and BF of IDVGA3 had significantly positive marking effect on carcass depth(P<0.05). Genotype BE and DE of INRA005 had significantly positive marking effect on daily gain(P<0.05).
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