凡纳滨对虾幼虾体重性状在低温波动环境下的遗传参数分析

基于凡纳滨对虾(Litopenaeus vannamei) 40K SNP 芯片分型信息估计了低温波动条件下幼虾体重性状的遗传参数, 为凡纳滨对虾耐低温新品种的选育提供基础数据。利用来自 40 个家系的 4000 尾凡纳滨对虾幼虾, 通过地下井水降温的方式使养殖温度从 30 ℃骤降至 20 , 24 h ℃ 自然回温后稳定 4 d。该降温–回温–稳定过程重复 3 次, 继续养殖 15 d后进行体重和存活性状测试。与对照群体相比, 低温波动条件对凡纳滨对虾幼虾生长影响显著(P＜0.05), 而对存活性状影响不显著(P＞0.05)。根据个体的系谱信息构建 A 矩阵; 利用 40K SNP 芯片对 159 尾家系亲本及其同胞个体进行 SNP 分型, 复合 SNP 信息和系谱信息构建 H 矩阵。基于 A 和 H 矩阵, 利用个体动物模型估计体重性状的方差组分和遗传参数。低温波动条件下凡纳滨对虾幼虾基于 A 矩阵获得体重的遗传力为 0.37±0.07, 基于 H 矩阵获得体重的遗传力为 0.40±0.08, 为高遗传力水平。经交叉验证, 基于两种不同矩阵的预测准确性和偏差无明显差别。研究结果表明, 低温波动条件下凡纳滨对虾幼虾的体重性状表现出丰富的遗传变异, 多代选育可能获得较大的遗传进展。     

中国对虾新品种“黄海2号”的培育

选取中国对虾“黄海1号”、“即抗98”2个养殖群体,朝鲜半岛南海群体、乳山湾群体、青岛沿岸群体及海州湾群体4个自然群体,采用不平衡巢式交配设计方案,于2005年建立了中国对虾育种的基础群体.设计并建立了中国对虾的多性状复合育种技术,选育的目标性状为生长速度、白斑综合征病毒(white spot syndrome virus,WSSV)感染后的存活时间及养殖存活率.结果显示,养殖170 d收获体质量的遗传力为0.22,抗WSSV存活时间的遗传力为0.14,存活率的遗传力为0.03.采用BLUP法估算个体育种值,通过百分比加权的形式,分别赋予生长速度、抗WSSV存活时间和存活率的加权值为80％、15％和5％,并对性状育种值进行标准化,获得综合选择指数;按照每个家系及个体的综合选择指数大小进行家系间及家系内留种,并根据系谱信息,设计交配方案,将每代的近交系数控制在1％以内.选育4代后的统计结果表明,平均每代的遗传进展为生长速度,13.56％;抗病力,6.76％;存活率,5.05％.3个性状中,收获体质量的遗传力最高、加权最大,每代获得的遗传进展稳定在12％以上;抗WSSV存活时间与存活率遗传力较低,每代获得的遗传进展相对小且不稳定.实验培育的新品种“黄海2号”于2009年通过全国水产原良种委员会审定,可在适合中国对虾的养殖区进行推广养殖.     

凡纳滨对虾幼虾耐高温性状的遗传力评估

为探明高温对凡纳滨对虾幼虾遗传变异的影响,自2018年由国外引进的4个凡纳滨对虾种群(EGDB、PRMA、API、SIS)构建的育种群中随机选取40个全同胞家系,每个家系随机取100尾个体,分成2份放入指定的试验桶中,共计4000尾仔虾,采用水浴加热法,对试验桶进行升温并记录其相应的存活时间及温度,用单性状动物模型对其耐高温性状进行遗传参数的评估。结果显示：凡纳滨对虾仔虾各家系的耐热性为782.64～2074.33℃?h,表明凡纳滨对虾仔虾家系间的耐热性存在显著性差异;家系间耐热性值的变异系数为10%～68%;当水温由28℃升至40℃时,各家系的累计存活率为58%～99%;利用单性状动物模型结合系谱信息,获得凡纳滨对虾幼虾耐高温性状的遗传力估计值0.22±0.05,属于中等遗传力。试验结果表明,凡纳滨对虾幼虾耐高温性状具有较高的遗传变异水平,遗传改良的潜力较大。本试验结果可为凡纳滨对虾夏季高温养殖和耐高温品系的选育提供数据参考。     

近交对中国明对虾生长、存活及抗逆性的影响

以"中国对虾遗传育种中心"2个近交家系为基础培育近交群体,近交系数为0375;以"中国对虾遗传育种中心"选育的核心群体做对照群体.将实验对虾养殖60 d,每隔20 d测量体长与体质量.通过体长、体质量、存活率、耐盐力、耐温力和抗白斑综合症病毒(WSSV)感染能力6个指标来评价近交对中国明对虾生长、存活和抗逆性的影响.方差分析表明,近交群体和对照群体在体长、体质量和存活率这3个性状上差异显著(P＜0.05),近交衰退系数分别为-4.027 0%、-7.300 0%、-5.803 3%;而近交群体和对照群体在耐盐力、耐温力和抗WSSV感染能力3个抗逆性状上差异不显著(P＞0.05),近交衰退系数分别为0.084 1%、-0.739 4%、1.911 0%.研究结果表明,近交使中国明对虾生长、存活等性状产生显著的衰退,而对抗逆性这-性状没有显著影响.     

不同盐度下凡纳滨对虾生长和存活性状遗传评估

为揭示不同盐度环境对凡纳滨对虾家系体质量和存活性状的影响,本研究标记来自72个家系的4348尾对虾,在盐度30(HS组)和盐度15(LS组)条件下混养60 d,分析体质量和存活性状的遗传参数以及基因型与环境互作效应。结果显示,HS组的凡纳滨对虾平均体质量和存活率均高于LS组。估算体质量、存活性状遗传参数,结果显示HS和LS组体质量的遗传力估计值分别为0.51±0.08和0.30±0.07,属高遗传力;转换后存活性状遗传力估计值分别为0.22和0.39,也表现为中高遗传力水平。综合HS和LS组的数据,估算的体质量和转换后存活性状遗传力分别为0.45±0.07和0.31,均表现为高遗传力水平。然而由于收敛原因,在估计模型中未能包括共同环境效应,上述遗传参数估计值偏高。估算基因型与环境互作效应(G×E),结果显示两个盐度间体质量和存活性状均表现为高度遗传相关(0.81~0.90),G×E方差组分与加性遗传方差组分比值均小于0.5,G×E效应均不显著。研究表明,尽管凡纳滨对虾的生长和存活性状在两个盐度下存在一定差异,然而基因型与盐度的互作效应并不显著,由此认为在盐度15~30的范围内,不需要针对不同的盐度建立不同的选育系。     

中国对虾“黄海2号”新品种的培育

选取中国对虾“黄海1号”、“即抗98”2个养殖群体,朝鲜半岛南海群体、乳山湾群体、青岛沿岸群体及海州湾群体等4个自然群体,采用不平衡巢式交配方案设计,于2005年建立了中国对虾育种的基础群体。设计并建立了中国对虾的多性状复合育种技术,选育的目标性状为生长速度、白斑综合症病毒感染后的存活时间及养殖存活率。为最大限度消除环境差异对遗传方差的影响,在中国对虾家系构建过程中采用标准化程序培育苗种,经过对体长为3cm左右的幼虾进行荧光标记,每个家系标记后混合养殖测试。随机从每个家系中抽取同等数目的标记对虾分成2组,一组共同养殖在养殖池中,测试生长速度和养殖存活率,另一组在封闭的水泥池中进行WSSV感染实验,测试病毒感染后的存活时间长短。中国对虾遗传参数的估计结果表明,养殖170天收获体重的遗传力为0.22,抗WSSV存活时间的遗传力为0.14,存活率的遗传力为0.03。采用BLUP法估算个体育种值,通过百分比加权的形式,分别赋予生长速度、抗WSSV存活时间和存活率的加权值为：80%、15%和5%,并对性状育种值进行标准化,获得综合选择指数;按照每个家系及个体的综合选择指数大小进行家系间及家系内留种,并根据系谱信息,设计交配方案,将每代的近交系数控制在1%以内。选育4代后的统计结果表明,平均每代的遗传进展为：生长速度,13.56%;抗病力,6.76%;存活率,5.05%。三个性状中,收获体重的遗传力最高、加权最大,每代获得的遗传进展稳定在12%以上;抗WSSV存活时间与存活率遗传力较低,每代获得的遗传进展相对小且不稳定。实验培育的新品种“黄海2号”于2009年通过全国水产原良种委员会审定,可在适合中国对虾的养殖区进行推广养殖。为更快地培育抗病新品种,解决对虾养殖病害问题,进一步的研究需查明对虾抗病的遗传机制,提高抗病性状的选择强度,快速培育对虾抗病新品种。     

中国明对虾WSSV携带量、生长和抗WSSV育种值的相关性分析

为评估中国明对虾生长及抗WSSV能力与中国明对虾WSSV携带量之间的相关性,实验对130个中国明对虾家系进行生长及抗WSSV性能测试,对收集到的中国明对虾生长和抗病数据,输入“水产动物育种分析与管理系统”数据库,利用综合选择指数法估计中国明对虾各个家系的育种值。根据分析结果,选择出生长育种值最大的5个家系和最小的5个家系、抗WSSV育种值最大的5个家系和最小的5个家系,分别检测上述20个家系的亲虾、养殖50 d及170 d中国明对虾的WSSV携带量。结果显示,亲虾、50 d中国明对虾及170 d中国明对虾的WSSV携带量分别为0.190 8、0.286 6和0.232 9 copies/ng DNA,三者之间差异均不显著。亲虾、50 d中国明对虾和170 d中国明对虾的WSSV携带量与中国明对虾的生长育种值相关系数分别为 0.021、0.363和0.185,亲虾、50 d中国明对虾和170 d中国明对虾的WSSV携带量与抗WSSV育种值相关系数分别为0.033、0.048和0.019。研究表明,中国明对虾的生长育种值和抗WSSV育种值与中国明对虾体内的WSSV携带量均无显著的相关性。     

基于表型值和育种值的中国对虾生长、抗逆性状相关分析

利用单性状动物模型估计中国对虾170d的体重、抗WSSV存活时间和存活率3个性状的育种值,在家系水平上进行性状间表型值和育种值相关分析。估计的3个性状的遗传力分别为:0.22±0.16、0.14±0.12和0.03±0.021,并据此计算各性状个体育种值。家系性状表型值的相关分析表明,家系170d体重和抗WSSV存活时间之间存在一定程度相关(r=0.35,P<0.05),其余性状间相关系数很小,且差异不显著。3个性状家系育种值间的相关系数均较小,170d体重与抗WSSV存活时间的相关系数最高(0.038),170d体重与存活率,抗WSSV存活时间与存活率之间为负相关(r=-0.24,r=-0.027),并且统计检验未达到显著性水平。研究结果表明,利用多性状复合育种技术,培育综合性状优良的中国对虾新品种是一个正确而必要的育种策略。     

中国明对虾单个家系中与生长性状相关微卫星标记的初步筛选

以1个人工授精获得的中国明对虾(Fenneropenaeus chinensis)F2家系为材料,对其中80尾中国明对虾进行正态分布检验,选择19个稳定扩增的微卫星位点对每一个体进行扩增和基因分型,分析家系遗传信息.利用最小二乘法对微卫星位点与中国明对虾体长、全长、体质量性状进行关联性分析.采用SPSS 11.5软件作微卫星分子标记与经济性状的方差分析,考察各微卫星位点对体长、全长、体质量3个经济性状的影响程度.结果表明,中国明对虾体长、全长、体质量3个性状均呈正态分布(P＞0.05);相关分析得到,19个微卫星位点中RS0683和FC019两个微卫星位点与体长、全长、体质量呈显著相关(P＜0.05);同时对差异显著的位点进行不同基因型间经济性状的多重比较,RS0683标记座位AA基因型在体长、全长、体质量的表型效应上极显著高于AB、BB基因型(P＜0.01),表明该标记位点基因型AA与3种经济性状正相关;FC019标记座位的AA基因型体长、全长、体质量显著低于AB、BC基因型(P＜0.05),表明该标记位点基因型AA与3种经济性状呈负相关.     

凡纳滨对虾生长性状遗传参数的估计

采用平衡巢式设计方法和人工授精技术,每个雄体配3个雌体,构建了18个父系半同胞家系和54个母系全同胞家系.分别测定了每个母系生长到5月龄60个全同胞个体的体质量、全长、体长、头胸甲长、头胸甲宽、头胸甲高、第一腹节背高、第三腹节背高和第一腹节背宽9个生长性状,应用数量遗传学原理,采用方差和协方差分析的方法,估算了5月龄凡纳滨对虾生长性状的遗传力及各性状间的遗传相关及表型相关.结果表明,利用父系半同胞组内相关法估计的遗传力是凡纳滨对虾各生长性状遗传力的无偏估计值.其中,体质量、全长、体长、头胸甲长、头胸甲宽、头胸甲高、第一腹节背高、第三腹节背高和第一腹节背宽狭义遗传力的估计值分别为0.460、0.392、0.303、0.234、0.251、0.330、0.282、0.321和0.356,属于中高等遗传力范围,显示出较高的选择育种潜力.基于父系半同胞遗传协方差组分及表型协方差分别估计的各性状间的遗传相关及表型相关表明,各个性状间均表现出高的正相关,其中遗传相关在0.750 ～0.976,体质量—全长的遗传相关为最大(0.976),全长—第三腹节背高的遗传相关为最小(0.750),表型相关为0.507～0.947,体质量—全长为最大(0.947),第一腹节背高—头胸甲高为最小(0.507).经t检验,各性状间遗传相关及表型相关均达到极显著水平,表明以任意一个生长性状为参数进行选育,均可达到改良凡纳滨对虾生长情况的效果.     

Genetic analysis of the Pacific white shrimp (Litopenaeus vannamei): heterosis and heritability for harvest body weight

The aim of this study was to estimate heterosis and heritability for harvest body weight of the Pacific white shrimp (Litopenaeus vannamei) measured at commercial farm conditions. Heterosis and heritability were estimated using a base population from diallel crosses of eight introduced strains. The base population included 9936 shrimp from 207 families that were produced with 188 sires and 172 dams using a nested mating design by artificial insemination. Heterosis was calculated basing on the least squares means (LSM) of harvest body weight. The results showed that most of the hybrids (75%) have positive heterosis for harvest body weight, which ranged from ?13.36% (UA2 × UA5) to 13.80% (UA6 × UA5) with a mean of 2.41%. The high amount of heterosis manifested in the hybrids indicated the usefulness of these hybrids for improving the growth. Variance components and heritability for harvest body weight were estimated using an animal model. The heritability estimate for harvest body weight was 0.092 ± 0.082 (h²) when genetic groups were excluded from the pedigree, but it was decreased when genetic groups were included in the pedigree ( = 0.066 ± 0.050), implying that there are strain additive genetic effect and heterosis in the base population. However, the heritability estimates for harvest body weight were significantly different from zero (P < 0.05) and there was no significant difference between h² and (P > 0.05). The results from this study indicated that significant improvement for growth is possible through cross‐breeding and selective breeding in L. vannamei.     

Estimating reproductive success of brooders and heritability of growth traits in Asian sea bass (Lates calcarifer) using microsatellites

Asian sea bass (Lates calcarifer) is one of the most important marine food fish species in Asia and Australia. To estimate the reproductive success of broodstock and heritabilities of growth‐related traits, two independent full‐factorial crosses (PI and PII) were created by crossing 10 males and 10 females. At 90 days post hatch (dph), the body weight (BW) and total length (TL) of 804 individuals from PI and 900 individuals from PII were measured and tissues samples of each fish were collected. Parents and offspring were genotyped with nine polymorphic microsatellites. Out of 1704 offspring from the two crosses, 98.7% were assigned to their parents. In PI, 19 of 20 parents produced offspring, while in PII, only five parents contributed to offspring. Low contribution of parents to offspring could lead to reduced genetic variation in the next generation. Heritabilities for growth‐related traits were estimated using the pedigrees reconstructed using microsatellite genotypes. The estimates of heritability were 0.22±0.16 and 0.25±0.18 for BW, 0.31±0.14 and 0.24±0.21 for TL and 0.22±0.22 and 0.15±0.09 for Fulton's condition factor in the two crosses respectively. Body weights at 90 dph and at harvest (289 dph) were significantly correlated (r=0.601, P<0.01). Therefore, growth‐related traits could be improved by exploiting additive genetic effects through selective breeding, and broodstock candidates could be selected early in the production cycle.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

Variation in Body Weight and Total Length Among Families of White Bass,Morone chrysops,Fry After Communal Rearing

Variation in body weight and total length among 15 families of Phase I white bass, Morone chrysops, was evaluated in a communal pond. Trait heritabilities (h²) were estimated and family pedigrees were determined a posteriori using microsatellite molecular markers. Fry averaged 36.7 ± 2.6 mm and 0.53 ± 0.10 g across all families after 32 days of communal rearing. The number of offspring identified in our sample per family ranged between three and 28. There were significant differences between families in both body weight and length (P < 0.05). The families clustered into four overlapping groups, but family rankings differed by trait. Both traits showed low heritability (h ² = 0.07, length; h ² = 0.06, weight). Subsequent studies in white bass should include assessment of larger fish to obtain genetic estimates at different stages in the production cycle. This study represents the first effort to assess variation among white bass families for any growth-related trait using a communal rearing approach.     

Genetic parameter estimates for growth‐related traits of blunt snout bream (Megalobrama amblycephala) using microsatellite‐based pedigree

Blunt snout bream (Megalobrama amblycephala) is an herbivorous freshwater fish species native to China and has been recognized as a main aquaculture species in the Chinese freshwater polyculture system with high economic value. The genetic parameter estimates for important economic traits are needed for its selective breeding. The aim of this study was to estimate the heritabilities for its growth‐related traits and explore the genetic and phenotypic correlations among the traits using microsatellite‐based pedigree approach. Offspring from a mass‐spawning of 92 broodstocks (42 sires and 50 dams) were reared in a communal pond and nine microsatellites were used to identify the parents of each sampled offspring. Of 749 offspring randomly selected, 708 (94.53%) could be assigned directly to a single parental pair, which was used for heritability estimates. Data were analysed using the method of restricted maximum likelihood (REML) using animal model and the results showed that the heritabilities of body weight, body length, total length and body height were 0.65, 0.53, 0.53 and 0.50, respectively. High genetic correlations were found among these four traits. According to these results, selection for growth seems to be feasible in M. amblycephala and the other growth traits will be heightened accordingly with the selection based on body length.     

Heritability estimates for growth‐related traits in the Pacific oyster (Crassostrea gigas) using a molecular pedigree

Pacific oyster is one of the leading species in world aquaculture, but heritability estimation applying mixed‐family approach has not been actively pursued. In this study, heritability for growth‐related traits in the Pacific oyster was first estimated by creating a single cohort of 45 families in a full‐factorial mating design consisting of nine sires and five dams. A total of 270 offspring were analysed and parentage assignment inferred by six microsatellite markers achieved 100% success. All parents contributed to the spawn and a total of 42 full‐sib families were represented. Using an animal model, heritability estimates at 12 months of age were 0.49 ± 0.25 for shell height, 0.36 ± 0.19 for shell length, 0.45 ± 0.23 for shell width and 0.35 ± 0.17 for wet weight. Genetic correlation between shell height and wet weight was quite high (0.79 ± 0.25), suggesting that direct selection of shell height, which is an easily measurable trait, also improves wet weight. The results obtained in this study indicate that growth‐related traits could be improved by exploiting additive genetic effects through selective breeding.     

俄罗斯鲟早期生长性状遗传参数的估计

采用人工授精技术和家系标准化培育技术构建了30个俄罗斯鲟(Acipenser gueldenstaedtii)父系全同胞家系(包含6个母系半同胞组),培育至150日龄和410日龄时,分别从每个家系中随机测量50尾个体的体长和体重。利用ASReml软件进行方差组分的估计,应用多性状动物模型进行俄罗斯鲟生长性状遗传参数的估计。结果表明,150日龄俄罗斯鲟体长和体重的遗传力分别为0.16±0.055、0.18±0.058,410日龄俄罗斯鲟体长和体重的遗传力分别为0.18±0.070、0.094±0.049,不同日龄生长性状的遗传力均为低遗传力,表明俄罗斯鲟更适合大规模家系的育种方法;150日龄和410日龄俄罗斯鲟体长和体重2个生长性状的表型相关和遗传相关均为高度正相关,其中表型相关系数分别为0.91、0.85,遗传相关系数分别为0.62、0.57,说明对体重或体长进行选育,均能实现改良生长性状的目标;不同日龄俄罗斯鲟家系平均体重的平均变异系数高于平均体长,前者为29.09%、29.46%,后者为10.16%、8.43%,表明俄罗斯鲟体重性状更具选育潜力。本研究估测了俄罗斯鲟不同时期生长性状的遗传参数,旨在为下一步合理制定该物种育种方案提供参考依据。     

凡纳滨对虾(Litopenaeus vannamei)微卫星多重PCR体系的建立及其在家系亲权鉴定中的应用

为了在遗传分析研究中提高效率并节约成本,本研究从已报道的凡纳滨对虾(Litopenaeus vannamei)微卫星位点中选取多态性较高的位点,基于各位点的扩增片段大小及退火温度等因素进行微卫星位点的组合.通过不断优化位点组合、反应体系及反应程序,成功建立了1个五重、2个四重和1个三重PCR反应体系,并将其应用于11个凡纳滨对虾家系的亲权鉴定.结果显示,四组多重PCR体系中的16个微卫星位点在11个凡纳滨对虾家系中的平均等位基因数(Na)为6,平均多态信息含量(PIC)为0.5813,平均观测杂合度(Ho)为0.513,平均期望杂合度(He)为0.636.利用Cervus3.0软件,对已知系谱关系的11个凡纳滨对虾家系进行亲权分析,其第一亲本累积排除率(CE-1P)、第二亲本累积排除率(CE-2P)和双亲累积排除率(CE-PP)分别为0.99525487、0.99990862和0.99999986.进一步分析表明,当同时使用四组多重PCR体系进行亲权分析时,其模拟配对率和亲权鉴定准确率均为100％,全同胞和半同胞家系鉴别效果良好,表现出准确的鉴别能力.本研究所建立的四组凡纳滨对虾微卫星多重PCR体系均可为后续的凡纳滨对虾遗传多样性分析和亲权鉴定提供高效、准确的检测手段.     

Genetic parameter estimation of nine quantitative traits by a marker‐based method in Large Yellow Croaker,Larimichthys crocea (Richardson)

Large yellow croaker accounts for the largest biomass production of any maricultured fish in China. However, very little is known about the genetic parameters of its commercially important traits. As an initial step towards developing a selective breeding programme, genetic parameters of nine quantitative traits were estimated using a marker‐based method. Dorsal fin samples were collected to extract genomic DNA, and GBS method was employed to construct the libraries for sequencing. Genetic parameters were estimated by REML method through a genomic relationship matrix (G matrix) constructed by abundant genomewide SNPs. The nine traits were body weight (BWT), body length (BL), body height (BH), length/height ratio (LTH), body width (BWH), eviscerated weight (EW), gonad weight (GW), eviscerated weight/body weight ratio (REB) and swim bladder index (SBI). Estimates of heritability were 0.63 ± 0.11, 0.60 ± 0.11, 0.53 ± 0.11, 0.34 ± 0.11, 0.55 ± 0.11, 0.66 ± 0.11, 0.37 ± 0.10, 0.25 ± 0.08 and 0.71 ± 0.10 for the nine traits respectively. The relatively high heritability values may be derived from calculating the genetic relationship by high‐density SNPs. To illustrate that, we had studied on the variation of the heritability estimates with different number of SNPs evenly sampled from 29748 SNPs. The results showed that the estimates of heritability generally decreased when the number of SNPs reduced. There were relatively high phenotypic and genetic correlations between the pairs of BWT, BL, BH, BWH and EW, which indicated that genetic improvement for these traits could be accomplished merely by selecting one trait. The results obtained in this study may provide a reference for the later selective breeding programme.