中国荷斯坦牛LYZ基因多态性及其与乳房炎的关联分析

【目的】通过研究中国荷斯坦牛溶菌酶基因(lysozyme,LYZ)编码区多态性与乳房炎的关联性,寻找与乳房炎相关的分子标记,加快中国荷斯坦牛的抗病育种进程。【方法】利用PCR-SSCP技术对30个公牛家系的610头中国荷斯坦牛LYZ基因进行多态性检测,利用最小二乘均数法对LYZ基因的多态位点与SCS和305d产奶量进行相关分析【结果】LYZ基因的外显子1上存在115(TG)突变位点,突变使精氨酸变为亮氨酸;突变位点经PCR-SSCP法检测发现了3种基因型TT、TG和GG,频率分别为0.270、0.508和0.222,χ2检验表明中国荷斯坦牛在该位点偏离Hardy-Weinberg平衡;GG基因型个体的SCS最小二乘均值极显著低于TT基因型个体(P0.01),显著低于TG基因型个体(P0.05);GG基因型个体的305d产奶量最小二乘均值极显著高于TT基因个体(P0.01),显著高于TG基因型个体(P0.05)。【结论】115(TG)位点GG基因型,对中国荷斯坦牛的SCS和305d产奶量有较大的遗传效应,可作为分子标记应用于奶牛乳房炎抗性的筛选。

Polymorphism of LYZ Gene and Its Association with Mastitis Trait in Chinese Holstein

【Objective】 The polymorphism of coding region of LYZ gene and its correlation with somatic cell score (SCS) and 305 d milk yield in Chinese Holstein were analyzed for the purpose of providing molecular markers in the marker-assisted selections (MAS) to accelerate the disease-resistant breeding progress in Chinese Holstein .【Method】 The polymorphism of LYZ gene was detected by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique in 610 Chinese Holstein cattle from 30 bull families. The associations between polymorphic sites of LYZ gene and SCS and 305 d milk yield were analyzed by the least square mean analysis. 【Result】 The 115(T＞G)mutation site was found in the exon1, and the mutation resulted in an amino acid change of Arg→Leu, for the polymorphic site, three genotypes (TT, TG and GG) were found in 610 Chinese Holstein by PCR-SSCP,and the frequency of TT, TG and GG genotypes was 0.270, 0.508 and 0.222, respectively. Chi-square tested showed Chinese Holstein was not in Hardy-Weinberg equilibrium at the site. Least square mean of SCS for GG genotype was highly and significantly lower than that for TT (P＜0.01), and significantly lower than TG genotype (P＜0.05). Least square mean of 305 d milk yield for GG genotype was greatly and significantly higher than that for TT (P＜0.01), and significantly higher than TG genotype (P＜0.05).【Conclusion】 GG genotype at 115(T＞G)site had a great genetic effect on SCS and 305 d milk yield in Chinese Holstein, which can be used as a candidate marker for mastitis resistance selection in dairy cattle.