Polymorphism of lyz gene and its association with mastitis trait in chinese holstein | 中国荷斯坦牛LYZ基因多态性及其与乳房炎的关联分析

中国人. 【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305 d产奶量进行相关分析【结果】LYZ基因的外显子1上存在115(T＞G)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(P＜0.01),显著低于TG基因型个体(P＜0.05);GG基因型个体的305 d产奶量最小二乘均值极显著高于TT基因个体(P＜0.01),显著高于TG基因型个体(P＜0.05)。【结论】115(T＞G)位点GG基因型,对中国荷斯坦牛的SCS和305 d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。

英语. 【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.