Studies O N Candidate Gene Of Meat Performance And QTL Mapping Of Growth And Development Traits In Goat

A total of 501 individuals was sampled from seven goat populations: Introduced Boer goat (YJ, n=49), selected breeding Boer goat(CF, n=50), Lubei White goat (LB, n=50), F1 generation goat from Boer×Lubei (F1, n=105), F2 generation goat (F2, n=172), Wendeng dairy goat (WD, n=30) and Laoshan dairy goat (LS, n=45).The genetic structure of the populations, the correlations between the polymorphisms of genetic markers and meat performance were studied by PCR-RFLP, PCR-SSCP and DNA sequence analysis methods. Furthermore, quantitative trait loci(QTL) for early stage growth and development traits were detected by microsatellite markers and WinQTLCart2.0 software in F2 population. The main goals were to understand the molecular genetic information concerned candidate gene loci, to look for the molecular marker or QTL of economic traits in order to provide scientific information for the protection and development of genetic resource, carrying out the molecular marker assisted breeding. The results were as follows: 1 Polymorphism of the F1/R1 locus in GH (Growth Hormone) gene and its correlations with meat performance (1) Two Boer goat populations, F1 and F2 were all at Hardy-Weinberg nonequilibrium state, the frequency of allele A in the four populations was higher than that of allele B. But three indigenous goat breeds were at Hardy-Weinberg equilibrium, The frequency of allele B was higher than that of allele A. Genotype distribution was significantly different among seven populations (P<0.01). (2) The correlations were observed between the locus and birth weight, weaning weight (P<0.01): The averages of birth and weaning weight of individuals with genotype AA were significantly higher than that of genotype BB (P<0.01). At the same time, the locus had significant genetic effect on the third, tenth, twelfth month withers height and the third month body length: There was significant difference among effects of three genotypes (P<0.05). That trend was AA>AB>BB in the above six indexes. The gene locus was relative to dressed weight and hindquarters meat weight (P<0.05): The number of individuals with genotype AB was significantly higher than that of genotype AA. 2 Polymorphism of IGFBP-3(Insulin-like growth factor-Ⅰbinding protein-3) gene and its correlations with some economic traits (1) PCR products from the gene locus were sequenced and the result showed that the sequence contains partial exon2, complete intron2, exon3 and partial intron3. The homology of the gene locus between meat goat and dairy goat, sheep, dairy cattle, porcine, mice and human was 99.1%, 98.1%, 94.1%, 79.0%, 34.4% and 54.1%, respectively. And the gene locus was very conservative among meat goat, dairy goat, sheep and dairy cattle and their homology was all above 90%. (2) A? G transition in the intron2 caused the gene locus to the polymorphisms of XspⅠin seven populations and the number of the individuals with genotype AG was more than that of genotype AA while the number of genotype AA was more than that of GG in every population. But all the populations were at Hardy-Weinberg equilibrium and genotype distribution was not relative to populations (P>0.05). We also found out that frequency of allele A was higher than that of allele G and the frequencies of allele A and G were nearly invariable in all the populations. (3) It was observed that the effect of genotype AG was more than that of AA while effect of AA was more than that of genotype GG for 3rd month body length and heart girth, 10th month body length and heart girth, 12th month body length, weaning weight and rib eye area. Furthermore the genetic effect of genotype AG was significantly higher than that of genotype GG. 3 Polymorphism of the F2/R2 locus in GH gene and its correlations with meat performance (1) Three mutations (-110 bp: T? C, -82 bp: T? A, -2 bp: C? T) caused the seven populations to three genotypes. Frequency of allele D was circa 0.2 in 5 non-dairy populations however they were 0.433 and 0.400 in 2 dairy goat populations, respectively. (2) The number of individuals with genotype CC was more than that of the other genotypes in non-dairy goat populations and the frequency of genotype CC was over 0.560.On the contrary, the number of individuals with genotype CD was more than that of the other genotypes in the dairy goat populations and the frequency of genotype CD was 0.600 and 0.578, respectively. The frequency of genotype DD was all lower than that of the others in seven populations and the frequency (0.133) of genotype DD of Wendeng dairy goat was the highest in the seven populations, but the seven populations were at Hardy-Weinberg equilibrium (P>0.05). Genotype distribution was relative to populations (P<0.01) and it indicated that the genetic structure was significantly different between dairy goat and non-dairy goat (P<0.01). (3) The results indicated that the correlations were not found between genotypes at the gene locus and body weight, body measures and carcass traits (P>0.05). 4 Polymorphism of the F3/R3 locus in GH gene and its correlations with some economic traits (1) Two mutations (-314 bp: T? C, -163 bp: C? deletion) caused the seven populations to three genotypes. Frequency of allele F was higher than that of allele E in Lubei White goat while the frequency of allele E was higher than that of allele E in the other populations. All populations were at Hardy-Weinberg nonequilibrium. The correlations between genotype distribution and populations was found out (P<0.01), and the genetic structure was significantly different between dairy goat and non-dairy goat. (2) The correlations between genotypes at the gene locus and birth weight, weaning weight, 12th month body weight, dressed weight, GR value, 10th and 12th month body length were found (P<0.05): the average values of above seven indexes of individuals with genotype EE were significantly higher than that of with genotype FF (P <0.05). 5 The sequence analysis about MSTN (myostatin) gene and its correlations with meat performance (1) Myostatin gene 5'-region in goat was cloned and it was 1344 bp. According to sequence analysis, it contains 5'-promoter, 5'-UTR and partial cds and enhancer sequence, CCAAT box, TATA boxes and start codon sequence were found. The homologies of the sequence of goat with sheep, dairy cattle, porcine, and mice were 98.2%,96.1%,81.2% and 59.4%, respectively. (2) The transition (C? T) at -662 bp in the 5'-promoter leaded to polymorphisms of TaqI and there were CC, CT and TT genotypes in the seven populations. The frequency of genotype CC in Boer goat was higher than in the three indigenous goat populations, but the frequency of genotype TT in Boer goat was lower than in the three indigenous goat populations. The frequency of allele C was higher than that of allele T in the Boer goats,while it was contrary in the three indigenous goat breeds. Except for Boer goats, 5 other populations were at Hardy-Weinberg nonequilibrium (P<0.01). The correlations between genotypes in the MSTN gene 5'-region and weaning weight, meat weight and hindquarters meat weight were found (P<0.01): The average values of weaning weight and meat weight of individuals with genotype CC were significantly higher than that of individuals with genotype TT (P<0.05) and the averages of hindquarters meat weight were not significant difference among different genotypes (P>0.05). The average values of weaning weight, meat weight and hindquarters meat weight in genotypes CC, CT and TT went down in turn. At the same time, the correlations between this locus and liver weight was found (P<0.05): The average of liver weight of individuals with genotype CT was significantly higher than that of genotype TT and the significant difference in liver weight between other genotypes were not observed (P>0.05). (3) Two mutations (T? A and T? C) in the exon3 of myostatin gene caused the seven populations to three genotypes: NN, NM and MM. The frequencies of allele M in non-dairy goat populations were higher than in the indigenous goat breeds. Except for F1, the other populations were at Hardy-Weinberg equilibrium (P>0.05). At the same time , the genotype distribution in the exon3 locus among the populations was nearly same as 5'-region of myostatin. The correlations between the myostatin gene exon3 and meat weight, hindquarters meat weight and liver weight were observed (P<0.01): The genetic effects for genotypes were MM>NM>NN and the averages of meat weight, hindquarters meat weight and liver weight of individuals with genotype MM were significantly higher than that of individuals with genotype NN (P<0.05). (4) The individuals with genotype CT-NN and CT-NM were not detected in the seven populations. Beside this,the individuals with genotype TT-NN and TT-NM were also not detected in Boer goats, and the individuals with genotype TT-NM were also not found in F1. Furthermore, individuals with genotype TT-MM were also not observed in three indigenous goat breeds. The genetic interaction between two loci of myostatin gene exon3 and 5'-promoter affected significantly weaning weight, hindquarters meat weight and liver weight (P<0.05): The averages of the three indexes of individuals with genotype CC-MM were the highest among the compound genotypes. 6 QTL mapping of main growth and development traits in goat 6.1 The genetic linkage map of Chr. 1 in goat In this study, the genetic linkage map of Chr.1 in goat was constructed by Mapmaker/EXP3.0. The total number of genotyped markers was 13, of which DVEPC06 was located 3 cM from BM3205 first time. The map covered 175 cM and the mean interval was14.58 cM. 6.2 Composite interval mapping (CIM) A quantitative trait locus(QTL) affecting birth weight was detected between CSSM11 and CSSM32. Two quantitative trait loci affecting weaning weight were scanned between CSSM19 and BM3205, nearby BM1312, respectively. Two QTLs affecting 6th month weight were scanned between CSSM19 and BM3205, between BM4307 and INRA011, respectively. Two QTLs affecting 3th month body length were detected between CSSM11 and CSSM32, between INRA049 and LSCV06, respectively. Two QTLs affecting 3th month body height were detected between ILSTS004 and BM4307, between BM4307 and INRA011, respectively. Two QTLs affecting 3th month heart girth were scanned between CSSM32 and BM3205. Two QTLs were detected nearby INRA011 which affects 6th month heart girth and 6th month chest depth,respectively. 6.3 Multiple interval mapping (MIM) The results indicated that the detecting QTL ratio of CIM was higher than that of MIM, for example, MIM only detected one QTL for 3th month body length and for 3th month heart girth. But the other results from MIM were almost same as from CIM.