Genetic Variant of MYLK4 Gene and its Association with Growth Traits in Chinese Cattle

As a member of MYLK family, MYLK4 gene may play a vital role in muscle development. In this study, one novel single-nucleotide polymorphism (SNP) was identified the bovine MYLK4 by sequencing pooled DNA samples (pool-Seq) and forced polymerase chain reaction-restriction fragment length polymorphism (forced PCR-RFLP) methods. Overall, we reported one mutation (SNP1) in the intron 10 region within the bovine MYLK4 gene in 559 individuals representing five main cattle breeds from China (Nanyang, NY; Qinchuan; Jiaxian, JX; Pinan cattle; and Caidamu cattle, CDM). Genotype AA and allele A were predominant in the QC, PN, and XN populations. Association analysis with growth traits in the QC breed showed that the animals with genotype GG had significantly greater chest breadth and hip width (P?<?0.05). Meanwhile, the genotype GG was strongly associated with withers height and body length than those with genotype AA (P?<?0.01 or P?<?0.05) at 12 months in the NY breed. These statistical results exhibited that the MYLK4 gene might be a potential candidate gene to improve cattle’s growth traits, and the SNP could be used as molecular markers in early marker-assisted selection (MAS) in beef cattle breeding program.     

Analysis of the genetic variation of vascular endothelial growth factor gene in three Chinese indigenous cattle breeds

PCR–SSCP and DNA sequencing methods were employed to screen the genetic variation of vascular endothelial growth factor (VEGF) gene in 675 individuals belonging to three Chinese indigenous cattle breeds including Qinchuan (QC), Jiaxian Red (JX) and Nanyang (NY) breed. Three new single nucleotide polymorphisms (SNPs) (g.6765T > C ss130456744, g.6860A > G ss130456745, g.6893T > C ss130456746) were found. One SNP (g.6765T > C) was detected in intron II of VEGF gene in all three breeds and the other two SNPs (g.6860A > G, g.6893T > C) were in exon III of VEGF gene only in NY breed. Among them, two synonymous mutations of exon III were identified: CCA (Pro) > CCG (Pro) at position 65th amino acid (aa) and TGT (Cys) > TGC (Cys) at position 76th aa of VEGF(190aa) in NY breed. Our study revealed that NY breed exhibited the most abundant genetic diversity in VEGF gene within the three cattle breeds. Furthermore, JX cattle breed was more similar to QC breed than to NY breed. Our genetic data in the present study supported the hypothesis that the distribution pattern of Chinese indigenous cattle breeds was closely related to the geographical and climatic background again.     

A novel SNP of the <Emphasis Type="Italic">Hesx1</Emphasis> gene in bovine and its associations with average daily gain

As an essential repressor, the homeobox gene Hesx1/HESX1 is required within the anterior neural plate for normal forebrain development. Mutations within the Hesx1 gene have been associated with GH deficiency or combined pituitary hormone deficiency. We detected the polymorphism of Hesx1 gene by PCR-SSCP and DNA sequencing methods in 702 individuals from four Chinese cattle breeds. A novel single nucleotide polymorphism (SNP) (IVS1 + 382T > C) was detected. The frequencies of genotype TC in four breeds were 0.000–0.222. Polymorphism of the Hesx1 gene was shown to be associated with growth in the Nanyang breed. Individuals with genotype TC was significantly lower average daily gain than TT at 18 months (P < 0.05).     

Effects of genetic variability of the carpine homeobox transcription factor <Emphasis Type="Italic">HESX1</Emphasis> gene on performance traits

HESX1 plays a key role in the development of the forebrain and pituitary gland and produces potential effects on performance traits. The objective of this study was to detect and assess the associations of the possible polymorphisms of six loci within HESX1 gene with performance traits in Chinese 1,119 goats. Only one novel SNP (NM_001494116:g.307049A > G) locating on IVS1 + 348A > G was identified and detected by HaeIII forced-RFLP-PCR. The frequencies of allele “G” varied from 0.025 to 0.245 in analyzed populations with the Hardy–Weinberg equilibrium (P > 0.05). Genotypic and allelic frequencies were found to be significantly different in four breeds (χ² = 147.674, df = 6, P < 0.001; χ² = 157.250, df = 3, P < 0.001, respectively), implying that the distribution of genotypic and allelic frequencies of goat HESX1 gene was significantly associated with different goat utilities (cashmere, meat and dairy). Association analysis results revealed no significant effects of caprine HESX1 gene on body sizes in XNSN population (P > 0.05) and cashmere traits in IMWC population (P > 0.05). Significant statistical of HESX1 gene with body weight was found (*P < 0.05). The genotype AA showed significantly higher body weight than those of AG in 2-year-old age (*P < 0.05), while the AA genotype was senior to AG genotype in 4-year-old body weight trait (*P < 0.05). These suggestions indicated that the HESX1 gene has significant effect on goat body weight depending on ages, which is accordance with the function repressor of the HESX1.     

Effects of <Emphasis Type="Italic">Mbo</Emphasis>II and <Emphasis Type="Italic">BspM</Emphasis>I polymorphisms in the gonadotropin releasing hormone receptor (<Emphasis Type="Italic">GnRHR</Emphasis>) gene on sperm quality in Holstein bulls

The hypothalamic gonadotropin-releasing hormone receptor (GnRHR) plays an essential physiological role in reproductive function, which triggers the synthesis and release of luteinizing hormone and follicle stimulating hormone in the pituitary. The objective of this study was to investigate the effects of polymorphisms of GnRHR gene on the quality of fresh and frozen semen in Holstein bulls. The PCR-RFLP method was applied to detect G286A and T340C transitions determining MboII and BspMI polymorphisms, respectively, in the exon I of bovine GnRHR gene and evaluated its associations with sperm quality traits in 131 Holstein bulls. In polymorphic locus 286, bulls with the GA genotype had significantly higher sperm motility in frozen semen (FMOT) than GG genotype (P < 0.01). In polymorphic locus 340, bulls with heterozygote CT genotype had significantly higher sperm motility (MOT), semen volume per ejaculate (VOL), and lower abnormal spermatozoa rate (ASR) than homozygote TT genotype (P < 0.05). Bulls contained one A allele or C allele had a favorable, positive effect on sperm quality traits. These results indicate that GnRHR gene can be a potential marker for improving sperm quality traits, and imply that bulls with GA or CT genotype should be selected in breeding program.     

Three novel SNPs in the coding region of <Emphasis Type="Italic">PPARγ</Emphasis> gene and their associations with meat quality traits in cattle

The peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear hormone receptor that regulates adipogenesis and many other biological processes. In the present study, we carried out PCR–SSCP and DNA sequencing analyses to examine SNPs in coding region of the PPARγ gene. A total of 660 individuals from five Chinese cattle breeds were genotyped. We identified three SNPs and their associations with meat quality traits were analyzed in 108 Qinchuan cattle. Two missense mutations and one synonymous mutation were found: 200 A > G (genotypes AA, AB and BB) resulting in D7G change, the silent substitution 42895 C > T (genotypes JJ and JI) and 72472 G > T (genotypes CC, DC and DD) producing Q448H change, respectively. The frequencies of PPARγ-A allele were 0.86, 0.83, 0.80, 0.72 and 0.87 for Qinchuan, Nanyang, Jiaxian, Luxi and Xianan populations, respectively. The frequencies of PPARγ-J allele varied from 0.87 to 0.96 in the five populations. In the 72472 G > T locus, the frequencies of PPARγ-C allele were higher than PPARγ-D allele in the five populations, and ranged from 0.58 to 0.82. Least squares analysis revealed that in 42895 C > T locus, there was a significant effect on tenderness in 18-20 months Qinchuan cattle (P < 0.01), and in the 72472 G > T locus, animals with the genotype DC had lower mean values than these with genotype CC (P < 0.01) for back fat thickness in 18–20 months, and animals with the genotype DD had lower mean values than these with genotypes CC and DC (P < 0.01) for water holding capacity in 21–24 months (P < 0.01). The SNPs we have identified may contribute to establishing a more efficient selection program for improving of genetic characteristics in indigenous Chinese cattle     

Analysis of genetic variability at codon 42 within caprine <Emphasis Type="Italic">prion protein</Emphasis> gene in relation to production traits in Chinese domestic breeds

In this study, genetic variability at codon 42 within prion protein (PRNP) gene and its associations with production traits were investigated in 2002 goats from four Chinese domestic breeds. The frequencies of allele “A” ranged from 0.353 to 0.562 in analyzed goat breeds with Hardy–Weinberg equilibrium (P > 0.05) except Xinong Sannen (XNSN) dairy breed. The establishment of relationships between different genotypes and growth traits was performed in Inner Mongolia white Cashmere (IMWC) breed and revealed an association of the polymorphism with body weight at 7-year-old goats (P = 0.033). The individuals with genotype GG showed heavier body weight than those with genotype AA. Moreover, association analysis detected two significant associations between different genotypes and cashmere yield and fiber length in IMWC breed (P = 0.009, P = 0.048, respectively). In addition, three significant associations of different genotypes with density of milk (a.m. and p.m.), solids-not-fat of milk (P = 0.013, P = 0.009 and P = 0.002), respectively, were found in XNSN breed. Genotype GG had better milk quality than others. These findings suggested that the polymorphism of codon 42 within PRNP was a useful DNA marker for eliminating or selecting excellent individuals in relation to production traits in marker-assist selection breeding of goat.     

Single nucleotide polymorphisms of the prolactin receptor (PRLR) gene and its association with growth traits in chinese cattle

Genetic polymorphism of the prolactin receptor (PRLR) gene was detected by PCR-SSCP and DNA sequencing methods in 665 individuals from five Chinese cattle breeds. The results showed that at the P1 locus, three observed genotypes (AA, AB and BB), two linked SNPs (G1267A and T1268C), and one missense mutation (S18N) within a putative signal peptide were determined. The frequencies of haplotypes A and B in the five breeds were 0.596–0.802 and 0.198–0.404, respectively. Polymorphism of the PRLR gene was shown to be significantly associated with growth traits in the Nanyang breed. Individuals with genotype BB had greater hucklebone width, body weight and average daily gain than those with genotype AA at 6 months old (P < 0.01), as well as better body height, body length and heart girth when 6 months (P < 0.05). This study revealed for the first time that the PRLR gene is a promising candidate gene that affects growth traits in cattle.     

Novel SNPs of the bovine <Emphasis Type="Italic">GAD1/gad67</Emphasis> gene and their association with growth traits in three native Chinese cattle breeds

In this study, polymorphism in the exon 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11 of bovine NUCB2 gene was detected by PCR-SSCP and DNA sequencing methods in 686 individuals from three Chinese cattle breeds. Two haplotypes (M and N), three observed genotypes (MM, MN and NN) and two SNPs (NC_007313: g. 27451G>A, NC_007313: g. 27472T>C) were detected. The frequencies of haplotypes M and N in inland Chinese three breeds were 0.531–0.721 and 0.279–0.469 respectively. The studied showed that Nanyang, Jiaxian Red and Qinchuan cattle populations were in Hardy–Weinberg equilibrium at SNPs locus of NUCB2 gene (P > 0.05). Polymorphism of the NUCB2 gene was shown to be associated with growth traits in Qingchuan and Nanyang cattle breed. The linkage of two mutant sites in the bovine NUCB2 gene had significant effects on body length, body weight, heart girth, and average daily gain at 24 months (P < 0.05). Results of this study suggested that the NUCB2-gene-specific SNP may be a useful marker for growth traits in future marker-assisted selection programmes in inland Chinese cattle.     

Analysis of caprine pituitary specific transcription factor-1 gene polymorphism in indigenous Chinese goats

Since mutations on POU1F1 gene possibly resulted in deficiency of GH, PRL, TSH and POU1F1, this study revealed the polymorphism of goat POU1F1-AluI locus and analyzed the distribution of alleles on 13 indigenous Chinese goat breeds. The PCR-RFLP analysis showed the predominance of TT genotype and the frequencies of allele T varied from 0.757 to 0.976 in the analyzed populations (SBWC, Bo, XH and HM). Further study, distributions of genotypic and allelic frequencies at this locus were found to be significantly different among populations based on a χ²-test (P < 0.001), suggesting that the breed factor significantly affected the molecular genetic character of POU1F1 gene. The genetic diversity analysis revealed that Chinese indigenous populations had a wide spectrum of genetic diversity in goat POU1F1-AluI locus. However, the ANOVA analysis revealed no significant differences for gene homozygosty, gene heterozygosty, effective allele numbers and PIC (polymorphism information content) among meat, dairy and cashmere utility types (P > 0.05), suggesting that goat utility types had no significant effect on the spectrum of genetic diversity. X. Y. Lan and M. J. Li equally contributed to this work.     

<Emphasis Type="Italic">CAPN1</Emphasis> markers in three Argentinean cattle breeds: report of a new InDel polymorphism within intron 17

In this study, the genotype distribution and allelic frequencies of CAPN1 (Calcium activated neutral protease) single nucleotide polymorphisms (SNPs) were analyzed taking advantage of the different genetic backgrounds provided by Hereford, Brahman and Braford cattle. We report a new insertion/deletion (InDel) polymorphism, consisting of a change of seven nucleotides for only one nucleotide (TCTGGGT → C) within intron 17 of the CAPN1 gene. The segregation pattern of this polymorphism was analyzed together with the markers CAPN316, CAPN530 and CAPN4751 already described. The allele distribution of CAPN1 markers in the Braford crossbreed (3/8 Brahman 5/8 Hereford) is described for the first time. Four assays of allelic discrimination were designed: the tetra primer ARMS-PCR technique for genotyping the new InDel and the CAPN4751 marker, and a PCR-RFLP method for genotyping the markers CAPN316 and CAPN530. The genotypic and minor allele frequencies (MAFs) obtained showed that the InDel polymorphism does not provide redundant information to that already provided by the other CAPN1 markers and segregates differently between breeds, being a common SNP (MAF ≥ 0.05) in the herds with a high percentage of Bos indicus background. The high percentage of heterozygous individuals found in the Braford crossbreed for the markers assessed reveals enough genetic variation that could help to solve the tenderness problem of tropical-adapted cattle.     

Effect of polymorphism in the peroxisome proliferator-activated receptor gamma gene on litter size of pigs

The association of polymorphisms in peroxisome proliferator-activated receptor γ (PPARγ) gene with litter size was studied in Large White and Landrace pig. Three SNP loci (P1, P2 and P7) on PPARγ₂ gene were determined by PCR–SSCP and the results showed that there were A → G mutations at 220 and 324 bp in 5′-regulator region and at 147 bp in exon 6, respectively. Allele frequencies were analysed in two breeds. Information on 2341 litter records from 564 sows was used to analyse the trait total number born (TNB) and number born alive (NBA). In Large White, TNB and NBA of genotype BB for P2 locus were the lowest, and the TNB and NBA of third and following parities and all parities were 0.74 and 0.51 piglets per litter less (P < 0.001) than those of the highest genotype AB, respectively, but for P1 and P7 locus the beneficial genotype AA were more 0.4–0.8 piglets per litter (P < 0.05) than the inferior genotype AB. In landrace, TNB and NBA of the first parity of genotype BB for P1 locus were 2.0 piglets per litter higher than AA (P < 0.05), but for all parities the TNB and NBA of genotype BB were 0.66 and 0.97 piglets per litter (P < 0.05) higher than AA, respectively. At P2 locus, the TNB and NBA of the second parity of genotype AA were obviously higher than those of AB (P < 0.05). And at P7 locus, the TNB and NBA of each parity of genotype AA were both about 2 piglets per litter more than those of BB (P < 0.05). The results indicated that PPARγ gene was significantly associated with litter size in pigs.     

Flesh color association with polymorphism of the tyrosinase gene in different Chinese chicken breeds

In order to study genetic variation of tyrosinase gene in four different flesh color chicken breeds selected from special districts including Guyuan, Wenchang, Tibetan and Hisex chicken, five loci of the TYR gene exon-1 and one locus of 5′ flanking region were analyzed in PCR-SSCP and DNA sequencing. The results indicated that there were polymorphisms only at TYR1 and TYR3 locus. At TYR1 locus located in exon-1, there were three genotypes (TT, CC, TC), respectively, in three Chinese chicken breeds, and Genotype CC had not been detected in Hisex chicken. At TYR3 locus located in 5′ flanking region, there were three genotypes (GG, AA and GA) in Chinese local chicken breeds and genotype AA had not been detected in Hisex chicken breed. It was concluded that there were many variations of TYR gene in Chinese local chicken breeds. DNA sequencing of PCR products for different genotypes showed that there were two mutation sites, respectively, C to T at TYR1 locus and G to A at TYR3 locus. Mutation at TYR1 locus did not cause any amino acid variation. The chi-square analysis revealed that there were significant statistical differences generally between flesh color and the two loci among four chicken populations (P < 0.01). Our results suggested that the flesh color was related to genotype of TYR gene in Chinese chicken breeds. This study provided original information for elucidating the possible roles of exon-1 of TYR gene and 5′ flanking region in chickens with different flesh color chicken.     

Polymorphisms of caprine <Emphasis Type="Italic">POU1F1</Emphasis> gene and their association with litter size in Jining Grey goats

Seven pairs of primers were designed to amplify 5′ promoter region, six exons and partial introns and to detect the polymorphisms of POU1F1 gene in five goat breeds with different prolificacy. The results showed that six mutations were identified in caprine POU1F1 gene including C256T in exon 3, C53T and T123G in intron 3, and G682T (A228S), T723G and C837T in exon 6. The former four mutations were novel SNPs in goat POU1F1 gene. The 53 and 123 loci were in complete linkage disequilibrium in five caprine breeds. Regarding the 256 locus, the Jining Grey goat does with genotype CT had 0.66 kids more than those with genotype CC (P < 0.05), while does with genotype GT had 0.63 (P < 0.05) kids more than those with genotype GG at the 682 locus. The present study preliminarily showed an association between allele T at the 256 and 682 loci of POU1F1 gene and high litter size in Jining Grey goats. Totally 16 haplotypes and 50 genotypes were identified at the above six loci in POU1F1 gene of five goat breeds. Three common haplotypes (hap2, hap3 and hap4) were identified in five goat breeds joined. Four specific haplotypes (hap7, hap9, hap11 and hap13) were detected in Jining Grey goats. The predominant haplotype was hap1 (35.29% and 48.25%) in both Jining Grey and Guizhou White goats, while hap4 (50%) in Boer goats, and hap2 (42.86% and 38.75%) in both Wendeng Dairy and Liaoning Cashmere goats. The most frequent genotypes at six loci in the above five goat breeds were hap1/hap2 (14.38%) and hap1/hap4 (14.38%), hap1/hap2 (38.60%), hap4/hap4 (40.91%), hap2/hap4 (26.53%), hap2/hap5 (20.00%), respectively. The Jining Grey goat does with nine genotypes analyzed of POU1F1 gene showed no obvious difference in litter size.     

Polymorphisms of <Emphasis Type="Italic">STAT5A</Emphasis> gene and their association with milk production traits in Holstein cows

The STAT5A gene was studied as a candidate gene for five milk production traits (milk yield at 305 days, protein percentage, fat percentage, lactose percentage and dry matter percentage) in Holstein cows. According to the sequence of bovine STAT5A gene, two pairs of primers (P1 and P2) were designed to detect polymorphisms of STAT5A gene in 401 Holstein cows by PCR-RFLP and PCR-SSCP. The results showed that the products amplified by primers P1 and P2 displayed polymorphisms. For P1, three genotypes (AA, AG, and GG) were detected, and the frequency of AA/AG/GG was 0.252/0.486/0.262, respectively. Sequence analysis revealed a single nucleotide substitution A–G at 14217 bp (GenBank NC_007317) of bovine STAT5A gene while compared GG genotype with AA genotype. The differences of the least squares means for the four milk production traits (milk yield at 305 days, fat percentage, lactose percentage and dry matter percentage) between AA, AG and GG were not significant (P > 0.05). Least squares mean of protein percentage for AG or GG was significantly higher than that for AA (P < 0.05); the difference of the least squares mean for protein percentage was not significant between AG and GG (P > 0.05). For P2, three genotypes (CC, CT, and TT) were detected in Holstein cows, and the frequency of CC/CT/TT was 0.751/0.234/0.015, respectively. Sequencing revealed an insertion CCT at 17266 (NC_007317) of bovine STAT5A gene while compared CC genotype with TT genotype. The differences of the least squares means for the three milk production traits (protein percentage, lactose percentage and dry matter percentage) between CC, CT and TT were not significant (P > 0.05). Least squares mean of milk yield at 305 days for TT or CT was significantly higher than that for CC (P < 0.05); the difference of the least squares mean for milk yield at 305 days was not significant between TT and CT (P > 0.05). Least squares mean of fat percentage for CC or CT was significantly higher than that for TT (P < 0.05); the difference of the least squares mean for fat percentage was not significant between CC and CT (P > 0.05). The results preliminarily indicated that allele G of A14217G polymorphic site of STAT5A gene is a potential DNA marker for improving protein percentage in dairy cattle, 17266indelCCT polymorphic site of STAT5A gene is a potential DNA marker for improving milk yield at 305 days and fat percentage in dairy cattle.     

Polymorphisms of caprine <Emphasis Type="Italic">GDF</Emphasis>9 gene and their association with litter size in Jining Grey goats

The exons 1, 2 and flanking region of growth differentiation factor 9 (GDF9) gene in five randomly selected does of Jining Grey, Boer and Liaoning Cashmere goats were amplified and analyzed. Thirteen nucleotide differences were identified in GDF9 gene between sheep (AF078545) and goats. Four SNPs (G3288A in intron 1, G423A, A959C [Gln320Pro] and G1189A [Val397Ile] in exon 2) were detected in four goat breeds with different prolificacy, in which G3288A was a new SNP in goats. The results showed that loci 3288, 423 and 1189 in Boer goats, loci 3288 and 423 in Guizhou White goats, loci 423 and 1189 in Liaoning Cashmere goats were all in complete linkage disequilibrium (D′ = 1, r ² = 1), respectively. In moderate (Boer goat) and low prolificacy (Liaoning Cashmere goat) breeds, linkage analysis indicated that there were more fervent linkage disequilibrium among loci 3288, 423 and 1189 than high prolificacy (Jining Grey and Guizhou White goats) breeds. For the 959 locus, the genotype distribution showed obvious difference between high prolificacy breeds and moderate or low prolificacy breeds (P < 0.05 or P < 0.01). The Jining Grey goat does with genotype CC or AC had 0.81 (P < 0.01) or 0.63 (P < 0.01) kids more than those with genotype AA, respectively. The present study preliminarily showed an association between allele C at 959 locus of GDF9 gene and high litter size in Jining Grey goats. These results provide further evidence that the GDF9 gene may be significantly correlated with high prolificacy in goats.     

Polymorphism of <Emphasis Type="Italic">DLK1</Emphasis> and <Emphasis Type="Italic">CLPG</Emphasis> gene and their association with phenotypic traits in Chinese cattle

DLK1 and CLPG were located in DLK1-GTL2 imprinted cluster. They all affected muscle growth and meat tenderness. The functional importance of DLK1 and CLPG imply that the variation of the genes could affect the growth traits of animal. PCR-SSCP and sequencing were used to analyze the four loci of DLK1 gene and CLPG gene in 1109 individuals, which belong to eight breeds/species of bovidae, including cattle, buffalo and yak. A synonymous mutation (C451T) was detected in exon 5 of DLK1 in Qinchuan cattle, but didn’t change significantly with phenotypic traits. Three genotypes AA, AB and AC of CLPG were identified in Jiaxian cattle. The associations analyst of different genotypes showed that the individuals with genotypes AA and AC had a greater body weight and longer body length than those with genotype AB (P < 0.05 and P < 0.01, respectively); the AA individuals were different from those AB (P < 0.05) in the circumference of cannon bone. No polymorphism was observed in the other populations at other loci. These results were in agreement with the homology analysis: DLK1 and CLPG genes were in a highly conserved.     

Two novel cSNPs of <Emphasis Type="Italic">weaver</Emphasis> gene in Chinese indigenous goat and their associations with milk yield

Weaver gene plays an essential physiological role in the function of many organs, including brain, heart, kidney and endocrine cells, and also in the regulation of insulin secretion by glucose and/or neurotransmitters. Thus, weaver gene is an important potential candidate gene effecting on performance traits. The objective of this study was to detect the genetic variation of five loci within weaver gene by PCR-SSCP, DNA sequencing and forced PCR-RFLP methods in 1,019 Chinese indigenous goats. Two novel coding SNPs (XM_598993:m.864G>A; XM_598993:m.1224T>A) locating on P3 and P4 loci were identified and detected by MluI and AsuII forced PCR-RFLP, respectively. In the MluI analysis, the frequencies of goat MluI-A allele in the analyzed populations were 0.226, 0.248, 0.096 and 0.088 for XNSN, GZ, SBWC and XJWC, respectively. Genotypic frequencies were found to be significantly different in four breeds (χ² = 75.842, df = 6, P < 0.001); In the AsuII analysis, the frequencies of goat AsuII-A allele in the analyzed populations were 0.584, 0.441, 0.073 and 0.063 for XNSN, GZ, SBWC and XJWC, respectively. Genotypic frequencies were found to be significantly different among four breeds (χ² = 399.464, df = 6, P < 0.001). The frequencies of allele MluI-A and AsuII-A in XNSN and GZ populations were significantly higher than those of SBWC and XJWC goats. Association analysis with adjusted milk yield in the XNSN breed indicated that the animals with AsuII-AA genotype owned significantly higher adjusted milk yield than the ones with AsuII-TT genotype in the second lactation (P < 0.05). The observation suggested that the allele “AsuII-A” had the positive effects on adjusted milk yield in the second lactation.     

mtDNA Diversity and genetic lineages of eighteen cattle breeds from <Emphasis Type="Italic">Bos taurus </Emphasis>and<Emphasis Type="Italic"> Bos indicus</Emphasis> in China

In order to clarify the origin and genetic diversity of indigenous cattle breeds in China, we carried out phylogenetic analysis of representatives of those breeds by employing mitochondrial gene polymorphism. Complete cyt b gene sequences, 1140 bp in length, were determined for a total of 136 individuals from 18 different breeds and these sequences were clustered into two distinct genetic lineages: taurine (Bos taurus) and zebu (Bos indicus). In analysis of the cyt b gene diversity, Chinese cattle showed higher nucleotide (0.00923) and haplotype diversity (0.848) than the reports from other studies, and the animals from the taurine lineage indicated higher nucleotide diversity (0.00330) and haplotype diversity (0.746) than the ones from the zebu lineage (0.00136; 0.661). The zebu mtDNA dominated in the southern breeds (63.3–100%), while the taurine dominated in the northern breeds (81.8–100%). Six cattle breeds from the central area of China exhibited intermediate frequencies of zebu mtDNA (25–71.4%). This polymorphism revealed a declining south-to-north gradient of female zebu introgression and a geographical hybrid zone of Bos taurus and Bos indicus in China.