大口黑鲈生长性状相关标记的聚合效果分析

The effect of pyramiding growth-related genotypes in largemouth bass (Micropterus salmoides)

选择已经获得的8个与大口黑鲈（Micropterussalmoides）生长性状相关的分子标记，其中4个单核苷酸多态性标记分别位于IGF-I、POU1F1、PSSⅢ和MSTN基因上，4个微卫星位点分别是JZL60、JZL67、MisaTpw76和MisaTpwll7。从养殖群体中筛选出具有4个以上优势基因型数量的大口黑鲈亲鱼20尾进行群体繁殖，其中雌鱼9尾，雄鱼11尾。所产子代进行同塘饲养，9月龄时随机挑选288尾进行体质量测量与STR基因分型。结果显示：子代体质量为103-401g，含有生长优势基因型的数量在1-6之间，含有1-6个生长优势基因型的个体其平均体质量依次为227．83、239．56、258．81、273．02、302．50和305．60g，生长优势基因型的数量与大口黑鲈生长速度呈正相关。进一步分析表明子代中优势基因型的平均数量为2．99，相比亲本群体的优势基因型平均数量（2．36）得到提高。研究结果说明，利用有限的与生长相关的优势基因型进行聚合可以获得具有优良生长性状的大口黑鲈，也为下一步大口黑鲈分子标记辅助育种提供理论依据。

Gene pyramiding is a method of obtaining good varieties, which aims to produce individuals with one supe- rior economic trait, according to the optimal breeding scheme involving selection of favorable target alleles or linked markers after crossing basal populations and pyramiding them into a single individual. The largemouth bass （Microp- terus salmoides） is one of the most important freshwater fish in China. Previous research identified certain molecular markers related to growth traits. In this study, eight molecular markers including four single nucleotide polymorphisms （SNPs） and four simple sequence repeats （SSRs） related to the growth traits of largemouth bass were selected to amplify the genomic DNA of parent largemouth bass. The four SNPs were located in the IGF-I, POU1F1, PSSIII and MSTN genes; the four SSRs were located in the JZL60, JZL67, MisaTpw76 and MisaTpw117 genes. Twenty large mouth bass （9 females, 11 males） containing four or even more advantageous genotypes were selected as parents for population reproduction, which were selected from 196 individuals. About 5 000 offspring individuals were cultivated in one breeding pond （1 114 mE） and fed with frozen fresh fish. After 9 months of cultivation, the offspring had reached a mar-ketable size. Two hundred and eighty-eight individuals were randomly chosen to measure their weight and detect their genotype. The results showed that the number of advantageous genotypes in parents were 1-5 and the frequencies were 20.41%, 41.3%, 30.10%, 8.67% and 1.53% respectively. To aggregate the advantageous genotypes in the offspring, the parents that had 4 and 5 advantageous genotypes were selected. The number of advantageous genotypes was1-6 in all offspring and the average weights of 1 to 6 advantageous genotypes groups were 227.83, 239.56, 258.81, 273.02, 302.50 and 305.60 g, respectively. The number distributions of each population were 6, 100, 110, 44, 20 and 8. The frequencies of each population were 2.08%, 34.72%, 38.19%, 15.28%, 6.94% and 2.78%, respectively. A general linear model （GLM） was used to perform correlation analysis between the number of advantageous genotypes and growth traits. GLM analysis showed that the number of advantageous genotypes related to growth traits was positively corre- lated with weight. Individuals with five or six advantage genotypes were significantly different （P〈0.05） with those that had fewer advantageous genotypes. Further analysis suggested that the average number of advantageous genotypes is 2.99 in the offspring, which is truly improved compared with the average number of advantageous genotypes of the parent group （2.36）. The results indicated that it was useful to improve the growth trait of largemouth bass using limited advantageous genotypes related to growth traits, which also provided a theoretical basis for gene pyramiding breeding.