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1.
针对凡纳滨对虾生长和存活性状,本实验估算了零换水养殖模式下的遗传参数,分析该模式与大换水量养殖模式的基因型与环境互作效应(genotype by environment interaction effect,G×E),为后续留种、配种方案制定等育种规划工作提供依据。通过人工授精技术,定向交尾建立了51个凡纳滨对虾全同胞家系。利用荧光标记识别家系,采用零换水养殖模式混养52 d后,测量并记录2个养殖池中的3822尾存活虾的体质量、体长及性别等信息。采用线性(广义线性)混合效应模型和REML算法,基于个体动物模型和父母本阈值模型估计生长和存活性状的方差组分和遗传力。结果显示,收获体质量和存活率具有较大变异系数。收获体质量和体长的遗传力分别为0.49±0.08和0.43±0.07,均属于中高遗传力(h2≥0.15);存活的遗传力为0.11±0.03,属于低遗传力(h20.15)。收获体质量与收获体长的遗传相关系数为0.98±0.01;收获体质量和体长与存活的遗传相关系数分别为0.31±0.15和0.34±0.15。对于体质量和存活性状,零换水和大换水量养殖模式间的遗传相关系数分别为0.62±0.11和0.65±0.11,G×E效应显著(K0.5)。综上所述,凡纳滨对虾在零换水养殖模式下存在较高的遗传变异,但是与大换水量常规养殖模式相比,家系间存在较大的重排序效应,因此针对该养殖模式应单独建立选育系进行新品种培育。  相似文献   

2.
凡纳滨对虾生长性状遗传参数的估计   总被引:6,自引:3,他引:3       下载免费PDF全文
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.  相似文献   

3.
准确估计育种目标性状的遗传参数,评估其改良潜力,是制定育种方案、进行选择育种工作的重要前提条件。本研究对100个凡纳滨对虾(Litopenaeus vannamei)家系15000尾仔虾个体进行淡化和低盐养殖实验,分析了2个阶段家系间存活率的差异,并进一步估计存活性状的遗传力。结果显示,2个阶段存活率范围分别为19.3%~100.00%和11.86%~99.22%,平均存活率分别为66.7%和67.5%。家系幼虾期总体存活率为6.67%~90.67%,平均存活率为46.91%。统计分析显示,2个阶段家系间存活率差异极显著(P0.01),存活率的相关系数为0.61(P0.01),呈中度正相关(0.3r0.8)。利用加性效应(A)和加性+共同环境效应(A+C)模型分别估计了淡化、低盐度养殖以及合并2个阶段存活性状转换后的遗传力。基于A模型,淡化阶段、养殖阶段和合并2个阶段存活性状转换后的遗传力分别为0.46、0.41和0.53,与0相比,估计值均达到极显著水平(z2.58);基于A+C模型,3个阶段遗传力转换后估计值分别为0.06、0.05和0.07,与0相比,估计值均未达到显著水平(z1.96)。基于A模型和A+C模型,获得的2个阶段间家系存活性状育种值的相关系数分别为0.41±0.09和0.48±0.09。由于半同胞家系比例仅为47%,家系单独在网箱中测试,家系遗传效应与共同环境效应部分混淆,因此,基于A模型获得的遗传力估计值偏高,基于A+C模型获得的遗传力估计值偏低。本研究结果表明,通过多代选择育种,可以改良凡纳滨对虾幼虾淡化和低盐度养殖存活性能。  相似文献   

4.
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。  相似文献   

5.
基于选择指数法对凡纳滨对虾(Litopenaeus vannamei)生长和高氨氮耐受性进行选择,用3种方法评估选择效果:Ⅰ)比较选择系和对照系相关性状的育种值;Ⅱ)比较选择家系和对照家系的最小二乘均值;Ⅲ)比较选择系与对照系表型值,计算相关性状的现实遗传力、遗传获得,并采用BLUP法估算相关性状的遗传力及遗传相关。结果显示,生长性状的选择反应为0.493~1.039,高氨氮耐受存活的选择反应为0.028~0.046;凡纳滨对虾生长性状的现实遗传力为0.288~0.315,遗传获得为6.45%~20.16%,高氨氮耐受成活率的现实遗传力为0.016,遗传获得为2.09%;BLUP法估算生长性状遗传力为0.216~0.284,且显著(P0.05),高氨氮耐受性遗传力为0.028±0.026,生长性状间呈高度遗传正相关为0.871~0.948,体质量与高氨氮耐受性间的正遗传相关为0.180±0.032,且显著(P0.05)。研究表明,采用选择指数法选育一代后,生长性状提高明显,高氨氮耐受性提高较小;选育群体生长性状具有较大遗传改良潜力,如何快速提高选育群体的高氨氮耐受性有待进一步研究。  相似文献   

6.
为更加准确地评估凡纳滨对虾体长、体质量以及抗WSSV性状的遗传参数,实验利用8个微卫星位点对凡纳滨对虾69个家系母本和子代进行基因分型,并利用分型信息进行系谱重构和分子亲缘关系相关度的计算,以重构系谱、分子亲缘关系度以及物理系谱分别构建加性遗传相关矩阵,进而对体长、体质量和抗WSSV性状的遗传参数进行评估。最终通过交叉验证的方法,比较三者对遗传参数评估的预测能力以及准确性。分型结果显示,8个微卫星位点,共检测到166个等位基因,各位点等位基因数为12~45个,亲本和子代群体每个位点平均等位基因数分别为9.50个和18.13个,平均观测杂合度分别为0.618和0.709,平均期望杂合度分别为0.749和0.775,平均多态性信息含量分别为0.711和0.750,所有位点均表现高度多态性。遗传力分析结果显示,利用物理系谱、重构系谱以及分子亲缘相关度对体长的遗传力估计值分别为0.119±0.031、0.120±0.032、0.132±0.030,对体质量的遗传力估计值分别为0.176±0.039、0.182±0.040、0.172±0.034,对抗WSSV性状的遗传力估计值分别为0.135±...  相似文献   

7.
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。  相似文献   

8.
在水温27~29℃下,将平均体长7.01 cm的凡纳滨对虾Litopenaeus vannamei饲养在730 mm×530 mm×450 mm的水族箱中,每箱30只,盐度6、18和30,每个盐度组3个平行,饲养6周,探讨盐度对凡纳滨对虾血细胞吞噬与免疫相关因子基因表达的影响。结果表明:盐度30和18组凡纳滨对虾血细胞吞噬活性显著高于盐度6组对虾(P0.05),盐度18组血细胞吞噬活性最高。30和18盐度组凡纳滨对虾肝胰腺中Toll样受体(TLR)、免疫缺陷基因(immune deficiency,IMD)、酚氧化酶(PO)、过氧化氢酶(CAT)及溶菌酶(LZM)基因表达水平显著高于盐度6组(P0.05);18盐度组凡纳滨对虾血细胞中TLR、IMD、PO、SOD及LZM基因表达显著高于6盐度组(P0.05);盐度30组对虾的TLR基因表达水平显著高于盐度18组(P0.05),而盐度30组对虾的PO和CAT基因表达水平显著低于盐度18组(P0.05);其他免疫因子基因的表达水平没有显著性差异。综上,环境中盐度的变化可能通过影响凡纳滨对虾各组织的抗氧化能力、溶菌活性、识别能力和血细胞吞噬活性等,调控凡纳滨对虾细胞和体液免疫。  相似文献   

9.
设计了蛋白质含量为20.61%、30.52%、40.43%和50.34%的4种饵料(分别为CP20、CP30、CP40和CP50),研究饵料蛋白质含量对不同盐度下(分别为低盐度LS 2、中盐度MS 22和高盐度HS 32)凡纳滨对虾[(0.0144±0.0047)g]生长、成活及体成份的影响,测定了不同处理组对虾的肝胰腺指数(HIS)和肥满度(CF),试验为期8周.结果显示:(1)盐度对凡纳滨对虾的生长、成活、肥满度和灰分含量均有显著影响(P<0.05),而对肝体指数、体粗蛋白、体粗脂肪和水分无显著影响(P0.05),中盐度组对虾各指标均最高,其次为高盐度组,低盐度组最低;中、高盐度组对虾的增重率、特殊体重(长)增长率均显著高于低盐度组对虾(P<0.05),而中、高盐度组对虾的各生长指标无显著差异(P<0.05);(2)饵料蛋白质含量对凡纳滨对虾的各生长指标和体粗蛋白含量影响显著(P<0.05),对其它各指标影响不显著(P<0.05).各盐度下,对虾生长和体粗蛋白含量均随饵料蛋白质含量升高而升高,投喂CP20的对虾组显著低于其它各处理组(P<0.05);肥满度和肝体指数均先随饵料蛋白质含量升高至40.43%而升高,然后稍有下降;饵料蛋白质含量对各盐度下对虾成活率影响均不显著(P0.05).(3)双因素方差分析结果显示,盐度和饵料蛋白质含量,除对体灰分含量存着着显著的交互作用外(P<0.05),对其它体生化成份含量、生长及体形态指标的交互作用均不显著(P0.05).(4)饲料蛋白质含量明显影响了凡纳滨对虾肝胰腺的组织结构,投喂CP30和CP40饵料的对虾肝小体基膜完整,投喂CP40对虾的肝小体中还出现了大量的存储细胞(R细胞);而投喂CP20饵料的对虾肝小体分布松散,R细胞数量较小,并且部分肝小体基膜破损;而投喂CP50饵料的对虾的肝小体排列紧密,且B细胞内出现大量内容物质.结果提示,提高饵料蛋白质含量虽然在一定程度上加快对虾的生长速度和增加肥满度,但是并不能提高低盐底下凡纳滨对虾的成活率.饲料中蛋白质含量的不适宜,尤其是含量过低,会导致对虾肝胰腺的结构发生变化甚至发生不同程度的病理变化.  相似文献   

10.
凡纳滨对虾自交系与杂交系早期生长和存活的比较   总被引:4,自引:0,他引:4  
姚雪梅 《水产学报》2006,30(6):791-795
以2个不同遗传背景A、B凡纳滨对虾(Litopenaeus vannamei)群体为亲本,建立了凡纳滨对虾自交系和杂交系,比较其子一代的生长与存活。A是引自美国夏威夷海洋研究所的SPF凡纳滨对虾,B是在海南本地养殖多代选育不携带病毒的凡纳滨对虾。实验由自交组AA(A♀×A)、BB(B♀×B)和杂交组AB(A♀×B)、BA(B♀×A)4个实验组组成。结果表明自交组生长AA>BB,存活率BB>AA。由此看出2个群体生长和存活率存在较大差异,AA具有生长快优良性状,BB具有存活率高的优良性状。杂交组生长AB>BA,存活率BA>AB。杂交组与自交组生长和存活率比较:生长AA>AB>BA>BB,存活率BB>BA>AB>AA。两个杂交组在生长和存活率上均表现出母本和父本不同的优良性状,AB、BA组表现生长和存活率双重优良性状,杂交优势显著。杂交使生长和存活这两个表型性状都得到了改良。两个杂交组的生长和存活率比较发现杂交子一代遗传力偏向母本,即母系遗传占主导地位。  相似文献   

11.
壳白长牡蛎基因型与环境互作(G×E)效应分析   总被引:1,自引:1,他引:0       下载免费PDF全文
邢德  李琪  张景晓 《水产学报》2019,43(2):474-482
为探索壳白长牡蛎品系的壳色性状和生长性状的基因型与环境互作(G×E)效应,利用巢氏设计构建全同胞家系,每个家系分成两组分别在乳山和荣成海域进行养殖。利用线性混合模型和REML法分析11月龄壳白长牡蛎生长性状和壳色性状的遗传力及G×E效应。采用最佳线性无偏预测法(BLUP法)估计壳高和L~*两个性状的育种值,并通过加权获得综合育种值来筛选优良家系。结果显示,乳山组和荣成组的壳白长牡蛎生长和壳色性状的遗传力不同,分别为(0.14±0.08)~(0.62±0.18)和(0.01±0.03)~(0.78±0.19),可能存在尺度效应。以不同环境为固定效应,综合两个环境计算出的生长和壳色性状的遗传力为(0.02±0.02)~(0.51±0.09),然而由于部分全同胞家系缺失和模型不收敛的原因,估计模型中未包括母本/共同环境效应和显性效应,上述遗传力估计值偏高。本研究中生长和壳色性状在两个环境间的遗传相关为(–0.47±0.40)~(0.75±0.18),均小于0.8,表明壳白长牡蛎品系的生长和壳色性状都具有明显的重排效应,壳白长牡蛎品系其选育需要针对不同的养殖环境培育不同适应性的选育家系。综合育种值排名前20的个体其家系来源比例表明,家系G1和G21对于乳山海域表现出特殊的适应性,而家系G4、G22和G5对荣成海域环境具有特适性,家系G2则对两个环境具有普适性。研究为壳白长牡蛎品系的良种选育提供了重要的参考依据。  相似文献   

12.
The aim of this study was to estimate genetic parameters for spawning traits and growth traits in a breeding line of Pacific white shrimp, Penaeus (Litopenaeus) vannamei, selected for growth and survival. Traits studied were number of eggs (NE) and number of nauplii (NN) and female body weight at insemination (FWI) and body weight at 130 days of age (BW130). Genetic parameters were estimated using a multivariate animal model. Heritability for NE and NN were estimated as 0.13 ± 0.04 and 0.03 ± 0.04 respectively. The contribution to NN total variation due to ‘factors associated with male’ effect was estimated as 0.47 ± 0.07. In the cases of FWI and BW130, heritability was estimated as 0.44 ± 0.08 and 0.19 ± 0.03 respectively. Genetic correlation between FWI and NE was estimated as 0.49 ± 0.15, between FWI and NN as 0.54 ± 0.39 and between NE and NN as 0.27 ± 0.41, whereas the genetic correlations of FWI, NE and NN with BW130 were 0.30 ± 0.13, ?0.21 ± 0.19 and ?0.25 ± 0.38 respectively. Although it is important to perform more studies on this issue, our results found no evidence of a genetic antagonistic effect between female reproductive traits and body weight at harvesting (130 days of age) in P. vannamei.  相似文献   

13.
Three sets of full-sib families of Pacific white shrimp Penaeus vannamei Boone, produced from females in different reproductive condition (15, 45 and 75 days after ablation and start of production), were used to estimate heritabilities and genetic correlations of growth traits for several larval and grow-out stages of development. Heritabilities for early larval length (nauplii) were larger when estimated from families produced 45 and 75 days after ablation than when estimated from families produced 15 days after ablation, indicating a maternal effect caused by lower reproductive quality of the females used to produce the second and third sets. However, the better reproductive quality of females used to produce the first set resulted in significant density effects on larval length, presumably caused by different mortalities occurring among families during larval culture, which also resulted in an increase in the heritability values estimated for late post-larvae stages. After transfer to grow-out cages in a pond, all estimated heritabilities decreased initially, then increased again. The increase in heritabilities was associated with a negative correlation between growth and density in the cages at 58 days. Lowering densities at this age resulted in a decrease in heritability values at 97 days, but an increase again thereafter. The largest genetic correlation with abdominal weight, the trait of most interest for improvement in shrimp, was total weight. That was followed by cephalothorax weight, width of first abdominal segment, abdominal length and total length. Among these, the trait with a consistently large heritability at 58 and 97 days, and with a large genetic correlation with abdominal weight, was width of first abdominal segment. This trait might provide a secondary or indirect trait to improve abdominal weight when combined with total weight for a selection programme.  相似文献   

14.
During the development of breeding programme for Atlantic cod Gadus morhua L., in Iceland, genetic parameters were estimated for 1402 individuals, which were assigned with DNA profiling to 140 dams and 70 sires. The cod was reared in cages on the eastern and western coasts of Iceland from 2004 to 2005. At the average body weight of 1.8 kg, the estimated heritability (h2 ± SE) for body weight, gutted weight and the condition factor (CF) were 0.31 ± 0.06, 0.34 ± 0.04 and 0.24 ± 0.06 respectively. Genetic correlation (rG) in body weight between the two rearing locations was estimated as 0.95, which reflects a low G × E interaction. The estimated heritability for hepatosomatic index (HSI) and fillet yields was 0.061 ± 0.04 and 0.04 ± 0.04 respectively. The HSI and fillet yields were highly genetically correlated with body weight or 0.67 and 0.82 respectively. The genetic correlation between the CF and body weight was estimated as 0.31. There appears to be substantial amount of additive genetic variation for body weight suggesting that selection is likely to be successful. Low heritability for fillet yields and the HSI indicates less promise of genetic improvement. Assigning of parentage to individuals with DNA profiling was 80% successful.  相似文献   

15.
To estimate family BLUP breeding values and the heritability of body weight at harvest size (BW) in the Pacific white shrimp, Penaeus (Litopenaeus) vannamei, an experiment was conduced using information from two farm units of a Mexican hatchery and two shrimp population densities at each location. Data consisted of 12,658 shrimps that were siblings from 48 sires and 77 dams with a nested dam-sire structure. Shrimps were individually weighed at an average age of 130 days post-hatching. BW phenotypic mean (S.D.) was 18.2 (2.4) g, with values ranging from 8.4 to 30.0 g. Data were analyzed using univariate and multivariate models that considered BW within location by density pond environment as a different trait and included or not a common full-sib effect (c). The multivariate animal model included fixed effects of days from hatching and sex. For univariate models that included c effects, BW heritability (S.E.) estimates ranged from 0.24 (0.14) to 0.35 (0.18) across environments (heritability was zero in one environment). For multivariate models (excluding the environment with zero heritability) the heritabilities increased and ranged from 0.37 (0.06) to 0.45 (0.09). Standard errors of heritabilities and c effects were both drastically reduced in the multivariate analysis. Pairwise genetic correlations between environments were from 0.80 (0.08) to 0.86 (0.04). These differences may be indicative of genotype-environment interaction for BW at 130 days post-hatching. Statistical problems found to separate c from additive genetic effects both in univariate models were reduced using multivariate models. Correlation between family raw phenotypic means and family BV means from the multivariate analysis was 0.93 indicating a rather low risk of miss selecting superior families if BLUP solutions were neglected using replicated environment data. It is also concluded that use of incorrect statistical models or unreplicated data may lead to biased or inaccurate estimates of genetic parameters in shrimp breeding programs.  相似文献   

16.
本研究以凡纳滨对虾(Litopenaeus vannamei)61个家系为材料,开展了为期50 d的氯化物型盐碱水混合养殖测试,分析了各个家系的生长和存活性能。研究结果显示,凡纳滨对虾家系在氯化物型盐碱水养殖环境下的体重和存活率均存在显著差异,且家系间体重和存活率差异较大,变异系数分别高达36.26%和46.82%;凡纳滨对虾家系的绝对增重率均值和特定增重率均值分别为0.09g/d和1.82%/d,绝对增重最快的家系比绝对增重率均值高7.54个百分点,比增重最慢家系高12.95个百分点;凡纳滨对虾家系存活率范围为1.00%~63.33%,家系平均存活率为26.61%,家系最高存活率比家系最低存活率高了62.33个百分点,比家系存活率均值高了36.72个百分点。本研究结果表明:凡纳滨对虾家系在氯化物型盐碱水养殖条件下生长、存活存在较大差异,具有较大的遗传改良空间和选育潜力,本研究结果可为下一步的凡纳滨对虾盐碱水选育工作提供数据支持。  相似文献   

17.
Genetic parameters were estimated for survival of Macrobrachium rosenbergii using a fully pedigreed synthetic population formed by three introduced strains. The data included 107 398 progeny from 394 sires and 654 dams in six generations with a nested mating structure. The variance components and genetic parameters were estimated using a generalized linear mixed model with the probit link function. Available heritabilities in survival from the generation G3 to G5 ranged from 0.007 ± 0.020 to 0.066 ± 0.044 (> 0.05) using a model that included the common environmental effect (c). Across generations, low heritability (0.016 ± 0.012, > 0.05) was estimated using the model with inclusion of the c effect. There were statistically significant differences in the heritability estimates between different ponds for most generations. Moreover, the genetic correlation of survival between ponds over six generations varied from low to high (?0.0007 ± 0.17 to 0.80 ± 0.069) and was significantly different from unity. There were low correlation coefficients (?0.039 ± 0.096 to 0.342 ± 0.081) between body weight estimated breeding value (EBV) and survival EBV of families in different generations. The low heritabilities for survival are most likely caused by low genetic variation in the founder populations and reduced genetic variation because of consecutive selection.  相似文献   

18.
Heritability and genetic correlations for body weight at harvest size (BW), grow-out survival (SU), and log-transformed infectious hypodermal and hematopoietic necrosis virus (IHHNV) load (VLln) in Litopenaeus vannamei were estimated. Data were obtained in 2012 from a shrimp breeding population in Mexico using 12,440 shrimp for BW and 16,814 shrimp for SU, and quantitative polymerase chain reaction determinations from 160 full-sib families were obtained for VLln. DNA was extracted from pooled muscle samples of six shrimp per family for a total of 960 individuals. Heritability estimates for BW, SU, and VLln at the family mean and at individual levels were 0.24 ± 0.08, 0.02 ± 0.01, 0.42 ± 0.45, and 0.08 ± 0.11, respectively. Genetic correlation estimates of BW with SU, BW with VLln, and VLln with SU were 0.40, −0.04, and −0.57, respectively. Our results suggest that VLln has genetic variation and a favorable genetic association with BW and SU. No serious drawbacks were found from selection responses estimated using single-trait and multitrait indices to increase BW and SU and decrease VLln. Favorable correlated responses for IHHNV tolerance estimated as BW/VLln and SU/VLln were also found. This study offers new insights into the possibility of using IHHNV viral load as a possible selection criterion in L. vannamei breeding programs.  相似文献   

19.
Genetic parameters and genotype by rearing density interactions for growth traits and survival were investigated in Litopenaeus vannamei. A total of 3626 shrimps from 40 families in two densities (low density, 80 shrimps m?2; high density, 160 shrimps m?2) were measured for four growth traits, body length, body weight, cephalothorax length and abdominal segment length. Variance components and genetic parameters for growth and survival were estimated using a two‐trait animal model or a threshold (probit) sire and dam model. The common environment effect was excluded because it could not be partitioned effectively, likely because of high heritability. The heritability for growth traits varied from 0.21 to 0.44, indicating a moderate level. For survival, the back‐transformed heritability () was 0.36 ± 0.06 and 0.22 ± 0.04 for the low and high densities respectively. There were no significant differences in heritability for growth traits and survival between the two densities (P > 0.05). High genetic correlations (0.94–0.98) between the two densities for growth traits indicated a low genotype by density interaction and ranking effect across the environments, which suggested that these traits were controlled mostly by the same genes over the two densities. Therefore, selection in a low‐density environment should produce desired correlated responses for growth at a high density. Genetic correlation (0.77 ± 0.09) between the two densities for survival was moderate and significant, which indicated that the genotype by density interaction effect was moderate and low for survival under the two densities. Our results provide crucial information for use in L. vannamei breeding programmes in China.  相似文献   

20.
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.  相似文献   

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