[4]耐盐罗非鱼育种回交效应评估

    对罗非鱼2种回交子代、2种正反交子代（回交     

尼罗罗非鱼与萨罗罗非鱼回交一代与回交二代群体遗传特征的微卫星分析

利用尼罗罗非鱼(Oreochromis niloticus)第二代遗传连锁图谱中微卫星标记,对尼罗罗非鱼♀与萨罗罗非鱼(Sarotherodon melanotheron)回交一代(BC1)和回交二代(BC2)群体遗传特征进行了分析。结果表明,从28个微卫星位点中筛选出9个在尼萨回交一代和回交二代中存在差异的扩增位点,这些多态性位点可作为尼萨回交一代和回交二代群体遗传鉴别的重要依据。尼萨回交一代群体的平均观测杂合度为0.670,多态信息含量为0.423;回交二代群体的平均观测杂合度为0.460,多态信息含量为0.365,回交二代群体的遗传多态性低于回交一代群体。与回交一代相比,尼萨回交二代群体的平均有效等位基因数较为一致(BC1:Ne=2.17,BC2:Ne=2.20),基因型数较为一致,但纯合基因型比例、优势等位基因频率均有明显提高,表明连续回交导致后代遗传同质性提高。     

4种遗传型罗非鱼的耐盐慢性驯化表现

在实验室小水体中,对尼罗罗非鱼(Oreochromis niloticus,新吉富)、萨罗罗非鱼(Sarothrodon melanotheron)以及它们的杂交F1和F2("吉丽"罗非鱼)进行盐度梯度实验,观察其耐盐能力。采用4(遗传型)×4(水平或重复)随机区组设计。对照组全程维持淡水养殖;实验组起始盐度为0,盐度每天提高8直至实验鱼100%死亡。在水温保持(27.2±1.3)℃、正常投饵情况下,萨罗罗非鱼、尼罗罗非鱼、杂交F1及F2的50%死亡盐度平均值(MLS)分别为125.78±1.66、54.22±2.51、77.33±1.89和73.73±1.32;萨罗罗非鱼的累计存活率(CS)和MLS值均显著高于尼罗罗非鱼、杂交F1和F2(P<0.05);杂交F1和F2的CS值及MLS值均显著高于尼罗(P<0.05);F2和F1之间CS值和MLS值差异不显著(P>0.05)。     

尼罗罗非鱼、萨罗罗非鱼及其杂交子代胰岛素样生长因子(IGF-Ib)基因3'cDNA末端克隆及序列分析

为探讨尼罗罗非鱼、萨罗罗非鱼及其杂交子代(Oreochromis niloticuss♀×Sarotherodon melanotheron ♂)IGF-I基因结构差异,研究IGF-I基因与此3种基因型罗非鱼耐盐性能差异之间的关系,通过3'-RACE的方法,从鳃的总RNA分别获得其IGF-Ib基因的部分cDNA序列,长度分别为1 076 bp、1075 bp和1 079 bp,包含完整的开放阅读框(ORF)546 bp、一个终止密码及含polyA信号的3'UTR;ORF编码182个氨基酸,包括信号肽(44aa),成熟肽B区(29aa)、C区(10aa)、A区(21aa)、D区(8aa)及编码70aa的E区,二级结构为混合类型;与其他脊椎动物IGF-Ib序列的序列相似度达75.8%-100%;成熟肽A、B区高度保守,C区第82位后缺失2aa,E区第131位和159位分别缺失3aa和1aa;萨罗罗非鱼在E133位发生Ala/Pro氨基酸残基替换,与耐盐性强的莫桑比克罗非鱼和画眉罗非鱼一致,推测IGF-Ib基因E区选择性剪切与3种罗非鱼耐盐性能差异有关.     

尼罗罗非鱼与萨罗罗非鱼及其正反杂交后代的微卫星分析

微卫星（microsatellite）技术是近年来广泛应用的DNA标记,具有重复性好、较易操作和共显性的特点。在硬骨鱼类中表现出高度多态性,已在家系鉴定、遗传作图、群体遗传分析、育种以及系统发生研究等多个领域得到应用。尼罗罗非鱼（Oreochromis niloticus）是我国主要淡水养殖鱼类,生长快,耐盐能力一般;萨罗罗非鱼（Sarotherodon melanotheron）耐盐能力强,适合咸淡水养殖,但生长较慢。[第一段]     

尼罗罗非鱼♀×萨罗罗非鱼♂杂交后代的遗传分离分析

应用微卫星标记对尼罗罗非鱼(Oreochromis niloticus)♀×萨罗罗非鱼(Sarotherodon melanotheron)♂杂交后代(F1、F2)的遗传分离情况进行了初步研究.在86对微卫星引物中,筛选出21对在尼罗罗非鱼和萨罗罗非鱼中存在差异等位基因的特异性引物,共检测出59个等位基因,包含32个尼罗罗非鱼和24个萨罗罗非鱼特异等位基因.F1观测杂合度(Ho=0.998)大于 F2(Ho=0.739), F2有效等位基因数(Ne=2.48)、平均多态信息含量(PIC=0.497)与 F1的(Ne=2.45、PIC=0.489)相似.F1中所有位点均表现为尼罗罗非鱼与萨罗罗非鱼杂合基因型.F2中位点等位基因分离情况各异,通过卡方检验,有18个位点符合孟德尔遗传(P>0.05),2个位点GM145、UNH003表现为偏离孟德尔遗传(P<0.05),1个位点GM276不分离.在18个孟德尔遗传位点中, F2中尼罗罗非鱼特异等位基因频率为48.3%,萨罗罗非鱼特异等位基因频率为47.7%;基因型出现F1型、尼罗罗非鱼型、萨罗罗非鱼型的比例分别为58.2%、19.9%、21.9%.结果表明, F2较好地继承了F1的遗传杂合性,但也存在一定程度的分离.     

尼罗罗非鱼（♀）萨罗罗非鱼（♂）杂交F2与F3群体遗传特征的微卫星分析

利用罗非鱼第二代遗传连锁图谱中微卫星标记对尼罗罗非鱼( Oreochromis niloticus) ( ♀) 萨罗罗非鱼( Sarotherodon melanotheron) ( ♂) 杂交后代F2、F3 群体遗传特征进行了初步比较分析。结果显示, 28 对引物中有22 对引物能有效扩增, 未观察到杂交后代F2、F3 中有多倍体个体现象。筛选出7 个在尼萨罗非鱼杂交后代F2、F3 群体中存在差异的位点。杂交F2 群体平均等位基因( Na) 为2. 71, 平均多态信息含量( PIC) 为0. 466, 平均观测杂合度( Ho) 为0. 632; 杂交F3 群体平均Na为2. 14, 平均PIC 为0. 370, 平均Ho为0. 432, 杂交F3 遗传杂合性较杂交F2 降低。F2 自繁F3 过程中, F3 群体4 个位点的等位基因与F2 完全相同, 3 个位点的等位基因少于F2 , 且 F3 群体在2 个位点出现完全纯合, 杂交F3 群体位点等位基因呈现纯合趋势。研究结果为尼萨罗非鱼杂交世代遗传变异与杂交利用积累基础资料。     

尼罗罗非鱼（ ♀） × 萨罗罗非鱼（ ♂） F1家系亲权关系微卫星分析

利用尼罗罗非鱼（Oreochromis niloticus）第2代遗传连锁图谱标记,对3组不同尼罗罗非鱼（♀）×萨罗罗非鱼（Sarotherodon melanotheron）（♂）杂交F1家系内亲权关系进行分析。结果显示,86个微卫星位点中共筛选出20个在尼罗罗非鱼、萨罗罗非鱼中存在差异的扩增位点,含13个种间特异性和7个共享带差异位点。尼萨杂交F1中,平均等位基因2.90,平均多态信息含量0.439,位点多态性较高。3个尼萨杂交F1家系组间遗传距离0.362~0.504,组内个体间遗传距离0.245~0.316,组内遗传距离明显小于组间。利用3个种间特异位点组合,可对3个不同家系组父、母本个体进行鉴别。通过对各组亲本与子代位点基因型分析,家系A、B和C组分别使用4、8和12个特异位点组合进行亲权鉴定,累积排除概率分别为99.99%、99.99%、99.91%,家系A、B组分别含3个半同胞家系,家系C组含2对非同胞或4个半同胞家系。     

尼罗罗非鱼、萨罗罗非鱼及其杂交子代胰岛素样生长因子(IGF-Ⅰb)基因3′cDNA末端克隆及序列分析

为探讨尼罗罗非鱼、萨罗罗非鱼及其杂交子代(Oreochromis niloticus ♀× Sarotherodon melanotheron ♂)IGF-Ⅰ基因结构差异,研究IGF-Ⅰ基因与此3种基因型罗非鱼耐盐性能差异之间的关系,通过3′-RACE的方法,从鳃的总RNA分别获得其IGF-Ⅰb基因的部分cDNA序列,长度分别为1076bp、1075bp和1079bp,包含完整的开放阅读框(ORF)546bp、一个终止密码及含polyA信号的3′UTR;ORF编码182个氨基酸,包括信号肽(44aa),成熟肽B区(29aa)、C区(10aa)、A区(21aa)、D区(8aa)及编码70aa的E区,二级结构为混合类型;与其他脊椎动物IGF-Ⅰb序列的序列相似度达75.8%～100%;成熟肽A、B区高度保守,C区第82位后缺失2aa,E区第131位和159位分别缺失3aa和1aa;萨罗罗非鱼在E133位发生Ala/Pro氨基酸残基替换,与耐盐性强的莫桑比克罗非鱼和画眉罗非鱼一致,推测IGF-Ⅰb基因E区选择性剪切与3种罗非鱼耐盐性能差异有关。     

尼罗罗非鱼五品系生长性能评估

在我国黄河流域,长江流域及珠江流域三个农业生态区,山东青岛,上海,浙江湖州及广州四个地区,在网箱,水泥池及池塘三种水体,单养或混养系统里,对五个尼罗罗非鱼品系,即吉富品系,“７８”吕系,“８８”品系,“埃及”品系以及“美国”品系,进行生长性能的评估。评估分一龄和二龄阶段跟踪进行,共十七个试验。生长性能试验结果证明,不论是在青岛,湖州,上海还是在广州不论是池塘、水泥池,还是网箱养殖,不论是混养还是养     

"新吉富"罗非鱼选育后期连续12个世代的选育效果分析

为了解"新吉富"罗非鱼(Oreochromis niloticus)选育后期世代在长期选择下获得的遗传进展,对"新吉富"罗非鱼选育后期连续12个世代(F_9～F_(20))的生长性能进行了连续12年(2005-2016年)的跟踪评估。结果显示:随着选育世代的累进,"新吉富"罗非鱼选育后期世代F_9～F_(20)的生长速度、体重变异系数并没有呈现持续升高或持续降低的趋势,而是在世代间出现了一定程度的波动。经过12个世代的连续选育,选育系F_(20)的生长速度比F_8提高了25.23%～69.34%,平均每代获得的相对遗传进展为2.00%～5.29%,不同世代的选育效果存在一定程度的变动。研究结果表明,在选育后期连续12代的混合选育过程中,"新吉富"罗非鱼选育系获得了持续的遗传进展,由此推测,对"新吉富"罗非鱼的选育工作尚未达到选育极限,选育系F_(20)仍具有进一步选育的潜力。     

丁香酚对罗非鱼的麻醉效果

对罗非鱼进行丁香酚药浴实验,研究丁香酚药浴浓度、药浴时间以及鱼体规格对麻醉效果的影响。结果表明:在10~120mg·L-1范围内,随着丁香酚药浴浓度的增加,罗非鱼麻醉时间逐渐缩短,苏醒时间逐渐增长,罗非鱼麻醉复苏率均为100%;丁香酚药浴浓度为45mg·L-1时,罗非鱼可以在3min内麻醉,5min内苏醒,为最适药浴浓度。在最适药浴浓度条件下,丁香酚对罗非鱼的麻醉效果与鱼的规格无相关性,且药浴时间超过120min,罗非鱼复苏率呈降低趋势,浸泡时间达到300min时,罗非鱼的死亡率为100%。     

Evaluation of Nile tilapia pond management strategies in Egypt

Five pond management strategies for Nile tilapia Oreochromis niloticus L. production were evaluated in 0.1‐ha earthen ponds in Egypt during a 145‐day production cycle. Pond management strategies developed by the Pond Dynamics/Aquaculture Collaborative Research Support Programme (PD/A CRSP) were compared with a traditional and a modified Egyptian pond management strategy. Young‐of‐year Nile (mixed‐sex or sex‐reversed) tilapia were stocked into ponds at 20 000 fish ha^?1. Sex‐reversed tilapia were stocked into chemical fertilization, organic fertilization plus formulated feed and feed only treatment ponds, whereas mixed‐sex tilapia were stocked into organic fertilization plus formulated feed and chemical plus organic fertilization plus formulated feed treatment ponds. Nile tilapia yields ranged from 1274 to 2929 kg ha^?1. Nile tilapia yields in organic fertilization plus formulated feed treatments were significantly greater than the yield from chemical fertilization ponds. PD/A CRSP pond management strategies did not produce significantly greater Nile tilapia yields than the traditional Egyptian system, but a larger percentage of harvested tilapia in the organic fertilization plus feed treatments were classified in the first and second class size categories compared with the traditional Egyptian system. Organic fertilization plus formulated feed pond management strategies had the highest net returns, average rate of return on capital and the highest margin between average price and break‐even prices to cover total variable costs or total costs.     

Mate selection in aquaculture breeding using differential evolution algorithm

An algorithm to perform mate selection in aquaculture breeding using a computational optimization procedure called “differential evolution” (DE) was applied under optimum contribution selection and mate selection scenarios, to assess its efficiency in maximizing the genetic merit while controlling inbreeding. Real aquaculture data sets with 8,782 Nile tilapias from five generations and 79,144 coho salmon from eight generations were used to optimize objective functions accounting for coancestry of parents and expected genetic merit and inbreeding of the future progeny. The mate selection results were compared with those from the realized scenario (real mates), truncation selection and optimum contribution selection method. Mate selection allowed reducing inbreeding up to 73% for Nile tilapia, compared with truncation selection, and up to 20% for coho salmon, compared with realized scenario. There was evidence that mate selection outperformed optimum contribution selection followed by minimum inbreeding mating in controlling inbreeding under the same expected genetic gain. The developed algorithm was computationally efficient in maximizing the objective functions and flexible for practical application in aquaculture breeding.     

Evaluation of potential probiotics isolated from saline tilapia in shrimp aquaculture

Integration of tilapia to shrimp culture is currently being practiced to minimize the growth of pathogenic luminous bacteria. The microorganisms that are associated in tilapia may contribute to the inhibition of the growth of Vibrio harveyi through the production of secondary metabolites. In this study, two Bacillus strains (MJA1.1, MJA2.1) isolated from mucus of tilapia were evaluated for their possible application in shrimp culture. The inhibitory property of these isolates against V. harveyi was determined in vitro using co-culture assay in a liquid medium. Also qualitative extracellular enzyme assay was conducted to assess whether the bacterial isolates produce extracellular enzymes. Furthermore, the potential use of these isolates as shrimp feed additive was tested. Thereafter, shrimps were exposed to lethal dose of ammonia (140 mg l^?1) to test the effects of the isolates in vivo. The results showed that in vitro co-culture assay after 72 h caused a significant decline in the population of V. harveyi in treatments with potential probiotic isolates. Both isolates showed protease, amylase, and cellulase activities. Although no significant difference was observed in growth, survival was significantly higher in shrimp fed with diets added with either of the isolates. The shrimp exposed to lethal dose of ammonia demonstrated better survival when supplemented with the probionts compared to the control group. Thus, the efficiency of the isolates in inhibiting V. harveyi population and the improvement of survival and resistance of cultured shrimp to ammonia stress indicate their potential as probionts for shrimp culture.     

橙色莫桑比克罗非鱼(Oreochromismossambicus)和荷那龙罗非鱼(O.hornorum)的选育效果评价

以橙色莫桑比克罗非鱼（Oreochromis mossambicus）和荷那龙罗非鱼（O.hornorum）为基础群体,分别对其进行选育,并对产生的选育系F4代的选育效果进行了评价。经过4代的选育,橙色莫桑比克罗非鱼和荷那龙罗非鱼的日增重率分别比对照系提高了27.96%和36.73%,差异显著（P0.05）,平均每代选育效应分别为6.99%和9.18%。F4代的体重变异系数分别为23.74%和22.17%,比对照组分别降低了24.83%和36.33%。而且第一次性成熟时这2种罗非鱼的平均体重都比对照系增加2倍以上,其杂交子代的雄性率达到了99.4%。试验结果表明,橙色莫桑比克罗非鱼和荷那龙罗非鱼的选育效果明显,F4代的生长性能有了显著提高,个体之间的生长速度趋于一致;也说明这2种罗非鱼F4代仍具有一定的选育潜力,对其继续进行选育是切实可行的。     

橙色莫桑比克罗非鱼（Oreochromis mossambicus）和荷那龙罗非鱼（O．hornorum）的选育效果评价

以橙色莫桑比克罗非鱼（Oreochromis mossambicus）和荷那龙罗非鱼（O．hornorum）为基础群体,分别对其进行选育,并对产生的选育系F4代的选育效果进行了评价。经过4代的选育,橙色莫桑比克罗非鱼和荷那龙罗非鱼的日增重率分别比对照系提高了27．96％和36．73％,差异显著（P〈0．05）,平均每代选育效应分别为6．99％和9．18％。F4代的体重变异系数分别为23．74％和22．17％,比对照组分别降低了24．83％和36．33％。而且第一次性成熟时这2种罗非鱼的平均体重都比对照系增加2倍以上,其杂交子代的雄性率达到了99．4％。试验结果表明,橙色莫桑比克罗非鱼和荷那龙罗非鱼的选育效果明显,F4代的生长性能有了显著提高,个体之间的生长速度趋于一致;也说明这2种罗非鱼F4代仍具有一定的选育潜力,对其继续进行选育是切实可行的。     

Truncation selection for BLUP-EBV and phenotypic values in fish breeding schemes

We have compared rate of inbreeding (ΔF) and genetic gain (ΔG) in truncation selection schemes for fish on best linear unbiased prediction (BLUP) estimated breeding values (EBVs; BTS) or phenotypic values (PTS) with one constraint on the number of tanks (100 or 200) to rear the families, e.g., until tagging size, and one constraint on the total number of selection candidates (3200 or 6400). Single trait selection was practiced for a trait with heritability of 0.1, 0.4 or 0.7 and 5, 10, 20, 50, 100 or 200 selected sires and dams were selected. When going from PTS to BTS, we found an overall increase of ΔG and ΔF of a factor of 0.07 and 1.45, respectively; that is, the increase of ΔG was moderate and accompanied by a dramatic increase of ΔF. In general, ΔF was reduced by increasing the number of tanks at a given number of selection candidates and by decreasing the number of selection candidates at a given number of tanks. ΔF was also reduced for schemes with high heritability because BLUP breeding value estimation then increases the weight on the individual's phenotype, which leads to a reduced correlation between BLUP estimated breeding values within a family, and fish from more families become selected. In practical fish breeding schemes, PTS seems preferable over BTS because BTS generally give unacceptable high ΔF (≫0.01) for these schemes with few but large families. PTS can, however, only be used for traits measured on the selection candidate, which makes PTS less valuable for schemes with comprehensible breeding goals, including, for example, growth, disease resistance, maturity and fillet quality traits. Several traits are measured today on sibs only.     

吉富品系尼罗罗非鱼选育过程中遗传变异的微卫星分析

采用微卫星标记技术对选育新品种新吉富罗非鱼（F8－9）群体、基础群体（F0）、以及选育中群体（F6－7）在选育过程中出现的遗传变异进行观察与分析。19个微卫星位点扩增后的等位基因数为3～11个,随引物不同而异,合计得到115个等位基因,大小在70～270 bp之间。五群体平均基因多样性指数分别为,F0：(0.3083±0.1834)、F6：(0.2982±0.1889)、F7：(0.2923±0.1898)、F8：(0.2572±0.1923)、F9：(0.2743±0.1597),表明随着选育的进展,群体呈现出纯化趋势。AMOVA分析表明,在总遗传变异中,93.24%来自选育群体内,仅6.67%来自选育群体间。群体间的校正偏差后相似性系数在 F0与F6、F7之间分别为0.943 5和0.942 2,相对较高;而在F0与F8、F9之间分别为0.933 2和0.930 3, 相对较低。遗传距离在F0与F6、F7之间分别为0.058 1和0.059 5,相对较小;而在F0与F8、F9之间分别为0.069 1和0.072 2,相对较大。配对比较Fst值在F0与F6、F7之间分别为0.037 68和0.064 37,平均 值为0.051 03;而在F0与F8、F9之间分别为0.060 93和0.075 87,平均值为0.068 40,有所提高。这些指标的分析结果表明,经9年9代选育,已在罗非鱼世代间造成程度虽小但却可监测到的遗传分化;同选育群体F6－7相比,\"新吉富罗非鱼\"（F8－9）在遗传上更为稳定。图1表4