Genetic variation measured by microsatellites among three strains of domesticated rainbow trout (Oncorhynchus mykiss, Walbaum)

Genetic variation fuels selective change in natural and captive populations. In establishing a broodstock for selective improvement, the level of genetic diversity is an important consideration because it provides an indication of the scope for selective progress. Three domesticated strains of rainbow trout, Oncorhynchus mykiss (Walbaum), were examined at nine polymorphic microsatellite loci to assess detectable levels of allelic diversity and heterozygosity within and differentiation among the strains. A total of 126 alleles were observed to segregate into unique multilocus genotypes for each of the 152 individuals assayed. There was an average heterozygosity of 71.5% at these nine loci, and an average of 14 alleles at a locus. Each locus was represented by alleles unique to at least two of the three strains. Deviations from Hardy–Weinberg expectations of genotype frequencies were detected in each strain. Subsequent analysis indicated sub‐structuring within strains leading to Wahlund effects that caused these deviations. Significant differences in genotype frequencies and pairwise F_ST values demonstrated that all strains were unique. The overall F_ST of 0.089 provides additional evidence of unique genetic diversity present in each strain, and agrees well with the degree of genetic variation found in rainbow trout across broad geographical ranges. The genetic diversity contributed by each population suggests that there is greater scope for selective improvement of numerous traits within a synthetic strain combining these three strains than within any individual strain.     

Genetic studies of growth in domesticated rainbow trout

The heritability of body weight and the form of the growth curve was investigated in two crossbred strains of domesticated rainbow trout. Growth rate was nearly exponential at young ages but slowed to nearly linear at older ages. An empirical equation was derived that related exponential growth constants to the observed growth patterns. Heritabilities of body weight based on full-sib families were estimated at six ages for each stock. Estimates made at young ages were similar to other estimates of body weight in salmonid fish. However, non-additive genetic variance, culling bias and common environmental effects may have inflated estimates made at older ages, as the estimates were extremely high, and these possible sources of confounding were known to exist in the experimental design.     

Genetic differences in lipid and dry matter content between strains of rainbow trout (Salmo gairdneri) and their hybrids

Observed phenotypic differences of lipid content between strains of rainbow trout and their hybrids cultured in small Canadian prairie lakes are related to differences in the size of fish and highly correlated with differences in growth rate. As a percent of dry matter mean lipid levels of different strains and their hybrids ranged from 32.5% to 45.9% in one experiment and from 11.6% to 24.3% in another. There were significant additive genetic differences in lipid content between strains, independent of differences in weight, and there also appeared to be significant non-additive × environment interactions.Phenotypic differences in percent dry matter were small compared to the differences in lipid content.     

Genetic basis of phenotypic differences between transplanted stocks of brown trout

Abstract– We present results from an experiment testing for the existence of genetically based phenotypic differences among populations of brown trout ( Salmo trutta L.) born and raised under entirely natural environmental conditions. Genetically tagged individuals from two stocks (A and B) were introduced into a drainage system in Sweden previously void of brown trout, and the first generation (F₁) progeny were sampled from two lakes during nine consecutive years. Phenotypic differences among groups of progeny (A, B, and the AB hybrid) are expected to reflect genetically determined dissimilarities between the introduced stocks. Phenotypic differences among progeny groups were observed for age at maturity and for migratory and reproductive behavior, and these characters are apparently determined by genetic factors to an extent that permit their detection even in the presence of confounding and naturally occurring sources of variation such as lake, age, cohort and year of sampling. There was also significant variation among offspring groups with respect to body size (length), but only a small proportion of the total variation in size could be attributed to stock differences. These genetically based stock characteristics may represent local adaptations, and the fishery management implications of these findings are discussed.     

吉富罗非鱼不同选育群体的遗传多样性

用微卫星和扩增片段长度多态性(amplified fragment length polymorphism,AFLP)分子标记对海南、广州和青岛吉富品系尼罗罗非鱼的遗传多样性和遗传分化进行了研究。9对微卫星引物和4对AFLP引物的分析结果一致。微卫星分析表明,青岛吉富鱼的平均等位基因数(4.8)、平均观测杂合度(0.528)、平均多态信息含量(0.605)最高,海南吉富鱼的平均等位基因数(4.4)、平均观测杂合度(0.479)、平均多态信息含量(0.549)最低。AFLP分析显示,青岛吉富鱼的多态位点比例(48.4%)和基因多样性(0.245)最高,海南吉富鱼的多态位点比例(36.3%)和基因多样性(0.147)最低。这些表明,青岛吉富鱼的遗传多样性最高,海南吉富鱼最低。遗传分化分析表明,两两群体间遗传分化显著(微卫星FST为0.07~0.11,P<0.01;AFLPFST为0.24~0.29,P<0.01)。AMOVA分析显示,大部分遗传变异(微卫星的分析结果为91.26%;AFLP的为67.6%)来源于群体内个体间,表明吉富鱼选育品系尚具有进一步选育的潜力。     

Genetic variance for growth in rainbow trout (Salmo gairdneri)

The possibilities of genetic improvement of growth of rainbow trout were investigated. Two half-diallel crossing experiments with three strains were performed. In the second experiment families within a strain or strain combinations could be identified. One hundred fish of each strain, strain cross or family were measured at five or four different ages. Differences between strains, crosses and between families within each of them were highly significant at all ages. In juvenile stages heterosis seemed to be present, although it was not statistically significant. Differences between strains became more pronounced as age advanced. Genetic variance within strains and strain crosses was large and appeared to increase with age. Genetic improvement by selection appears promising provided mass selection is not performed too early. The small F-values of preliminary expt. 2 may indicate strong competition within each group which tends to increase residual variability.     

Genetic population structure within streams: microsatellite analysis of bull trout populations

Abstract– We used six polymorphic microsatellite loci to investigate a potential metapopulation system in bull trout ( Salvelinus confluentus ) from five spawning localities in the Lightning Creek drainage, a tributary to Lake Pend Oreille, Idaho. The number of spawners as estimated by redd counts is low in all populations sampled. Analytic viability models indicate that local isolated populations of these sizes are unlikely to persist. We tested two hypotheses: (1) these are remnant populations that are vulnerable to local extinction, or (2) these populations are interconnected by migration and are being maintained at larger effective sizes than indicated by the redd counts (i. e. metapopulation dynamics). All populations within the Lightning Creek basin are significantly differentiated ( P > 0.005), and the allele frequencies appear to be stable among temporally separated subsamples within locations. It is therefore unlikely that extensive dispersal has linked tributaries in a manner consistent with a metapopulation structure. The low number of spawning individuals combined with the degree of isolation indicated by the genetic data suggest that extinction of the tributary populations is probable if temporal variability and small size is prolonged. However, these populations contain amounts of genetic variation similar to populations throughout the range of bull trout. Therefore, if the apparent demographic trends are reversed, these populations may recover without suffering the detrimental effects of a severe bottleneck.     

Electrophoretic characterization of three hatchery-reared strains of rainbow trout, Oncorhynchus mykiss (Walbaum)

Abstract. Significant differences were found in allelic frequency distribution among three strains of rainbow trout, Oncorhynchus mykiss (Walbaum). The isocitrate dehydrogenase ( IDH-3, 4 * 1.1.1.42) locus was fixed in two of the strains while the superoxide dismutase ( SOD-I * 1.15.1.1) locus was absent in one of the strains.
Similarity indices ranged from 0·973 to 0·988 on the scale of 1·000 among pairwise comparisons of the strains while Nei's genetic distance was 0·012 between Mount Lassen and Manx, 0·025 between Mount Lassen and Tagwerker and 0·027 between Manx and Tagwerker. Gene diversity was highest in the Mount Lassen strain, followed by Manx, with Tagwerker having the least. These differences in gene diversity were attributed to breeding and management practices used at the hatchery. The need for characterization of strains of rainbow trout, especially in crossbreeding programmes that aim to increase genetic variation, was emphasized by these results.     

Genetic effects and growth performance in pure and hybrid strains of rainbow trout, Oncorhynchus mykiss (Walbaum) (Order: Salmoniformes, Family: Salmonidae)

Progeny from a cross of two strains of rainbow trout, Oncorhynchus mykiss (Walbaum), displayed about 7% heterosis in their growth rate. Variance component analysis showed that dams accounted for 20.3% to 65.8% variability in growth while sires accounted for none. Maternal effects were significant, but showed a diminishing trend over the study period. Additive genetic effects were nonsignificant. The Mount Lassen strain was better in maternal ability which indicated that source of dam was important. Interactions between sires and dams were significant with source of dam being important. Heritability for weight based on half-sib sire component of variance was estimated at 0.020 ± 0.001 and 0.269 ± 0.016 based on the dam component. Heritability for growth rate was 0.27 ± 0.04 based on the sire component and 0.88 ± 0.35 based on the dam component. Fulton's condition factor was lower in the hybrids. Egg size was correlated with fish size in the early growth phase. It was concluded that crossbreeding of rainbow trout strains could be advantageous owing to the display of hybrid vigour in the progeny.     

[08]利用配合力和微卫星标记预测虹鳟品系间的杂交优势

用10对SSR引物对渤海、丹麦、道氏、挪威、加州5个虹鳟(Oncorhynchus mykiss)品系进行遗传距离分析,以这些品系为亲本,用完全双列杂交方法建立50个全同胞家系,对F1个体体质量、体长进行配合力分析,以期预测各品系间配组的杂交优势.结果表明,5个虹鳟品系均具有较高程度的遗传异质性,10个位点的平均杂合度为0.816 3;在道氏品系与加州品系之间,遗传距离最大,达到0.717 3;丹麦品系与渤海品系间最小,仅为0.277 3.一般配合力以渤海品系为最高,依次为美国道氏品系、挪威晶系、丹麦品系、加州品系.而各品系配组中丹麦品系x加州品系、渤海品系×挪威品系、丹麦品系×道氏品系、渤海品系×道氏品系等均是特殊配合力较高的高效组合,对其重复试验显示,有望培育出杂种优势率较高的优势组合.实验证实,结合配合力与SSR标记分析,能有效地指导优势杂交组合的选配.     

虹鳟完全双列杂交试验生长性状遗传分析

通过来自渤海、丹麦、道氏、挪威和美国加州的5个虹鳟(Onchorynchus mykiss)养殖群体的完全双列杂交试验,分别在第249天、397天、552天和771天4个时间点观测了体重和体长变化。多重比较分析发现,20个杂交组合与对应5个自繁系之间在体重或体长性状上存在显著差异(P0.05)。采用最小二乘分析法估算了不同时间点体重和体长的一般配合力、特殊配合力、反交效应、母体效应及自繁效应值。结果显示,只有少数的遗传效应是显著存在的,而且这些遗传效应在不同性状和不同时间点的表现不尽相同。整个观测过程中,渤海群体和道氏杂交组合的体重和体长生长速度都是最快的,并且在体长上与对应的自繁系比较差异显著(P0.05)。体重性状上,道氏群体的一般配合力在249日龄和397日龄时最大,且均显著存在(P0.05);母体效应在249日龄时显著存在(P0.05),其效应值仅次于丹麦群体。体长性状上,道氏群体的母体效应在249日龄和397日龄时最大,且均显著存在(P0.05)。在所有杂交组合中,渤海和道氏杂交组合最为高效,体重性状上,整个观测过程中其特殊配合力为最大;体长性状上,其特殊配合力均为正值(0.30,0.03,0.17,2.55),在771日龄时为最大,并显著存在(P0.05)。研究表明,以道氏群体作为亲本之一可有效提高虹鳟后代生长性能,渤海和道氏群体的杂交组合效果最好,可以作为选育的基础群体。     

Isolation of peroxisomal enoyl-CoA hydratase in rainbow trout and immunochemical identification with the bifunctional enzyme

Peroxisomes are the sites for β-oxidation of long-chain fatty acids. The peroxisomal bifunctional enzyme (PBE) enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase catalyzes the second and third reactions of the β-oxidation system. Originally termed PPA-80 for peroxisome-proliferation associated 80,000 MW polypeptide, PBE levels are monitored to measure peroxisome proliferation in rodents and other species. The quantity of a 79,000 MW polypeptide in the light mitochondrial fraction of the liver, as analyzed by SDS-PAGE, increases when rainbow trout are exposed to peroxisome proliferating agents. This correlates with increases in acyl-CoA oxidase activity and peroxisome volume density. In the present study, peroxisomal enoyl-CoA hydratase was purified from trout liver and analyzed by immunoblotting with anti-PBE. A positive reaction with the 79,000 MW polypeptide band was observed providing strong evidence that this is the bifunctional enzyme.     

Biochemical growth characterization of fast and slow-growing rainbow trout strains: effect of cell proliferation and size

Concentrations of RNA and DNA, determined in two rainbow trout strains, Cornec and Mirwart, over a period of 9 months, were used to assess and characterize growth potential. More rapid growth and higher muscle nucleic acid concentrations in the Cornac strain trout, suggest a more metabolically active strain with higher rates of protein synthesis. On the other hand, the higher concentration of muscle DNA, in the Cornec strain, suggests a smaller cell size and a larger number of cells per unit weight issue. The faster decrease of DNA concentration, with increasing body weight, in the Mirwart strain, reflected a lower percentage of hyperplasia and consequently a lower capacity for growth.     

虹鳟源嗜冷黄杆菌的分离鉴定及致病性研究

为确定患病虹鳟的病原,本实验从患病鱼溃烂肌肉中分离到2株细菌,分别命名为CH06和CH07,经回归感染证实分离菌株为导致此次虹鳟患病的病原菌,并进一步对其形态特征、理化特性、分子特征、血清型及耐药性进行分析。结果显示,CH06和CH07株在TYES琼脂平板上呈煎蛋状外观,产黄色素,氧化酶和过氧化氢酶呈阳性,能水解明胶和酪蛋白,不能水解淀粉,不能利用果糖、半乳糖和七叶苷等。16S rRNA比对结果显示,CH06和CH07株与嗜冷黄杆菌模式株NBRC 15942的同源性分别为99.35%和99.42%。综合菌株理化和分子特性确定CH06和CH07株为嗜冷黄杆菌。利用多重PCR方法鉴定CH06和CH07株的血清型均为1型(Fd型);多位点序列分型(MLST)分析表明,CH06和CH07株的基因型分别为ST-12和ST-78型,且均属于CC-ST10克隆型。人工感染结果显示,CH06和CH07株对虹鳟幼鱼具有较高致病性,其半致死浓度(LD₅₀)分别为7.1×10⁵和1.1×10⁵ CFU/mL,攻毒剂量与临床病症出现时间呈反比,从人工感染实验鱼的肌肉、脾脏等组织中可重新分离到嗜冷黄杆菌。组织病理变化显示,病鱼肝细胞肿胀,空泡变性,部分肝细胞溶解坏死,细胞核溶解消失;脾脏充血、出血,淋巴细胞减少,红细胞和含铁血黄素增多;肌纤维间隙增宽、断裂、弯曲不齐,部分肌细胞肌浆溶解呈蜂窝状。CH06和CH07株对10种抗菌药物的耐药谱略有不同,均对氨苄西林和甲氧苄啶-磺胺甲噁唑敏感;CH06株对恩诺沙星、氟苯尼考等耐药,而CH07株对恩诺沙星和氟苯尼考中度敏感。本研究首次报道了我国虹鳟源嗜冷黄杆菌的分离鉴定及生物学特性,以期为虹鳟细菌性冷水病的防控提供科学依据。     

分离自腌干鱼的抗氧化发酵菌株的筛选及鉴定

以符合耐盐、耐高低温、产酸等要求和过氧化氢耐受能力为指标,对分离自传统腌干鱼制品的29株乳酸菌进行初筛,再以抗脂质过氧化率、羟自由基清除率和还原力为复筛指标评价了菌株不同组分的体外抗氧化能力,以期获得具有优良抗氧化活性的发酵菌株。结果表明,15株乳酸菌符合腌干鱼发酵要求,菌株间的抗氧化活性差异明显,其中以L4、L11和L21综合抗氧化活性最好。经VITEK-2微生物鉴定系统和16S r DNA分子鉴定,确定L4、L11和L21分别为戊糖片球菌（Pediococcus pentosaceus）、植物乳杆菌（Lactobacillus plantarum）和干酪乳杆菌（L.casei）。 

     

Effects of interaction between strains and environment on growth traits in rainbow trout (Salmo gairdneri)

Three strains and their three crosses were tested in two environments, floating nets and ponds. The genetic growth potential was reduced considerably in the much poorer pond environment. In addition, interactions independent of the average performance of the particular genotype were observed for weight and length but not for height and head length.     

两株草鱼呼肠孤病毒江西株的分离与鉴定

对从江西省南昌县莲塘镇的患病草鱼鱼种池塘采集到草鱼出血病疑似病样材料分离出的两株病毒株进行了鉴定。结果显示:用除菌过滤后的患病鱼肝脏、脾脏、肾脏组织浆滤液腹腔注射感染8～10 cm健康草鱼鱼种,5 d后试验鱼发病,可复制出自然发病症状,死亡率达50%以上,对照组未有死亡。用病样滤液接种草鱼肾细胞系(CIK),可产生细胞病变效应(CPE),病毒的TCID50分别为10-8.3/0.1 mL和10-8.0/0.1 mL。理化特性研究结果显示:氯仿、乙醚处理组病毒的感染力和对照组相比变化不显著。病毒基因组RT-PCR反应可扩增出目的片段,序列测定与分析结果表明,其与GenBank中GCRV(登录号为AF403392,AF239175)相应序列的同源性达99%以上。     

Voluntary feed intake,feed and nutrient utilisation in slow and fast growing rainbow trout strains

Two rainbow trout strains differing in their growth performance were used to study possible interactions between genotype, dietary composition and feed level on their feed utilisation efficiency and voluntary feed intake. Two diets (35 and 45 % of crude protein) and two feeding levels (to satiation or at a restricted level of 2 % of body weight), were used. The two diets were distributed, in duplicate, for each strain, during a four month growth trial. At the end of the experiment the digestibility of the two diets was determined in each strain, using chromic oxide, as a marker, and an automatic system for the faecal collection. The body composition of both strains was also analysed. The final weight of fish of the fast growing strain, fed to satiation, was significantly higher than that observed for fish of the slow growing strain. No significant differences were found between the strains's body weights, when a dietary restriction was made. Results observed for the feed-gain ratio were also similar between the two strains. The apparent digestibility coefficient (ADC) of dry matter and energy were significantly different between the two diets but similar for both strains. Concerning protein digestibility no significant differences were observed for diets, although one of the strains appeared to show a higher ADC for protein. Body composition as well as nitrogen and energy retention were similar for both diets and strains.