Comparative Performance of Four Strains of Nile Tilapia (Oreochromis niloticus) in Brackish Water Ponds in Indonesia

Four selectively bred strains of Nile tilapia (Oreochromis niloticus) were evaluated for production in brackish water ponds in Indonesia. Survival to 124 days was relatively low for all four strains (39%–48%), and growth during the later stages of the trial was poor (SGR < 1.5 %/day) due to water quality deterioration in the pond. Although the ‘Red’ tilapia strain demonstrated the best production parameters, red-colored tilapia bring lower prices in both our test markets (South Sulawesi and Aceh provinces). Of the four strains, the genetically enhanced supermale Indonesian tilapia?×?genetic improvement of farmed tilapia (GESIT×GIFT) cross provided the best economic return.     

Electrophoretic evidence for extensive hybrid gene introgression into commercial Oreochromis niloticus (L.) stocks in the Philippines*

Abstract. The usefulness of isozyme and protein markers in identifying tilapia species and their hybrids is demonstrated Genetic characterization of Oreochromis niloticus populations from commercial farms, experimental stations, and government hatcheries in Luzon, Visayas and Mindanao in the Philippines indicates well-established introgression with O mossambicus Genetic differentiation of the O niloticus stocks, measured by Nei's genetic distance, was highly correlated with O mossambicus gene content The implications of these results for tilapia genetic improvement are discussed.     

Growth and survival rate of three genetic groups fed 28% and 34% protein diets

The strain by nutrition interaction in body weight and survival rate was examined by testing three genetic groups (Selection and Control lines of the GIFT strain, and Red tilapia) at two levels of protein in the diet (28% and 34%). The GIFT strain of Nile tilapia (Oreochromis niloticus) has been selected for high‐breeding values for body weight, whereas the Control was contemporaneously maintained and selected for breeding values of body weight close to the population mean. The Red tilapia (Oreochromis spp) was unselected at the time of the experiment. There were a total of 6000 fish at stocking in the study (2000 fish per genetic group). During the grow‐out period of 147 days, within each genetic group, the fish were randomly assigned to either a 28% or a 34% protein diet. Survival rate during grow‐out averaged 72%. A total of 4335 fish were harvested, with individual body measurements and survival recorded. The effect of genetic group accounted for the largest proportion of variation in body weight and survival, followed by sex and protein level. Across the two dietary protein levels, the GIFT strain had the highest growth. The difference in body weight between the Control and Red tilapia was not statistically significant (P > 0.05). Responses in growth to dietary protein levels also differed between genetic groups. No differences (P > 0.05) in body weight were found in the GIFT selection and Control fish fed 28% or 34% protein diets. However, body weight of Red tilapia was greater in the high‐ than in the low‐protein diet. In contrast to body weight, survival rate from stocking to harvest was affected by protein level. The high‐protein diet significantly improved survival rate, averaging 24% across the three strains. The overall results indicate significant effects of genetic group and dietary protein level on both body weight and survival rate; however, the interaction between strain and dietary protein levels was small and possibly unimportant for these traits. It is concluded that the 28% protein diet used in the selection programme for the GIFT strain results in the selection of genotypes that can perform well under commercial feeds.     

Polymorphic microsatellite differences among four cultured populations of two selected tilapia strains

Genetic diversity plays a vital role for maintaining economically important traits in fish populations. The goal of this study was to assess the genetic variability among four tilapia populations in China. Two populations named XA (Oreochromis aureus, 30 samples) and AN (Egyptian Oreochromis niloticus, 24 samples) were gathered from Freshwater Fisheries Research Center (FFRC), and the other two named AL (O. aureus, 30 samples) and AJ (Egyptian O. niloticus, 30 samples) were from Guangxi Fisheries Research Institute (GFRI). GFRI introduced AL and AJ from XA and AN, and selected them for generations. We want to know if AL and AJ have genetic changes after selection and generations. Fifteen polymorphic microsatellite markers were used. Our results indicated that the four tilapia populations showed moderate genetic variability. The polymorphism information content (PIC) of the four populations was from 0.28 to 0.39; A_e was from 1.67 to 2.15; the H_e was from 0.35 to 0.46; the genetic similarity indexes were from 0.94 to 0.69 and also the clustering result showed that these four populations were highly related. There were no significant changes in genetic variation between late‐introduced population and early‐introduced population of O. aureus. Our results helped to understand the genetic variability of tilapia populations in China and for future marker‐assisted selection for important economic traits.     

Performance of genetically improved Nile tilapia compared with red hybrid tilapia fed diets containing two protein levels

A 10‐week feeding trial was conducted to investigate the interaction between tilapia genotype and dietary protein level on the growth, feed utilization efficiency and body composition of Nile tilapia [Oreochromis niloticus L., F₉ generation of genetically improved farmed tilapia (GIFT) strain] and red hybrid tilapia (Oreochromis sp.). Two isoenergetic diets (15.5 kJ g⁻¹ diet) containing 25% or 35% crude protein were formulated and fed to triplicate groups of tilapia (12.8±0.2 g) at a fixed daily ration of 4% of their body weight. The growth performance of the GIFT tilapia fed 25% or 35% dietary protein was significantly higher (P<0.05) compared with red tilapia at either protein level. Increasing the dietary protein level by 10% led to a further 10% increase in the final weight of GIFT tilapia but no further increase was observed in the weight gain of red tilapia. Growth was influenced by the interaction between diet and tilapia genotype. Feed conversion ratios were 14% and 33% better in GIFT tilapia compared with red tilapia fed the 25% or 35% protein diet respectively. Protein efficiency ratio and net protein utilization were influenced by both diet and tilapia genotype, but not the interaction between the two. The apparent digestibility coefficients of dry matter and protein did not differ significantly between the two diets and tilapia genotypes but lipid digestibility was 1.2–4.7% higher for the GIFT tilapia. Tilapia whole‐body protein content was significantly influenced by both diet and tilapia genotype. The higher growth potential, better feed utilization efficiency and higher body protein content of GIFT tilapia compared with red tilapia should have a positive impact on tilapia farming in terms of production costs.     

When low genetic variability in feral and hatchery-reared tilapia becomes a vicious circle: Oreochromis niloticus from Oaxaca, Mexico

Several tilapia species in Mexican reservoirs have been used as food source for more than 40 years but little effort has been devoted to the conservation and genetic selection of those species. Our objective was to evaluate genetic variability in feral (n = 59) and hatchery-produced (n = 58) Oreochromis niloticus stocked in the Benito Juarez dam. Allozyme analyses for 13 enzymatic systems and general proteins yielded 27 genetic loci. Seventeen loci were polymorphic in at least one sample. The observed heterozygosity was lower than expected and the imbalance in the Hardy–Weinberg equilibrium in almost all loci was caused by heterozygote deficiency. The inbreeding coefficient was 84%. Although the evidence suggests moderate genetic differentiation, it is probable that a great proportion of the source of hatchery organisms is from feral organisms. According to our results, management of the hatchery strain is inadequate, therefore other breeding strategies are needed to increase the genetic variability of O. niloticus from Oaxaca.     

尼罗罗非鱼出肉率与可量性状的相关性

运用统计分析方法研究了吉富品系和埃及品系尼罗罗非鱼(Oreochro misniloticus)2龄成鱼雌、雄个体的出肉率和可量性状之间的相关性。结果显示,尼罗罗非鱼的平均出肉率为38.68%,雄性个体出肉率比雌性个体略高,吉富品系出肉率比埃及品系略高。尼罗罗非鱼出肉率与可量性状间存在较强的线性关系,拟合方程相关系数为0.985。在有显著意义的可量性状相关系数中(P0.01),与肉片质量和出肉率的相关性均最高的可量性状为体质量,相关系数分别为0.964和0.575;其次为体高、体长和体厚。而头长与肉片质量、出肉率均呈负相关关系。雄性个体的相关系数均高于雌性个体,在雄性个体中,出肉率与体质量的相关系数为0.630,与体高的相关系数为0.617,均为中等程度相关。对可量性状之间的比值与出肉率进行相关性分析,相关系数普遍比单个性状高,特别在雄性个体中表现明显。其中相关系数较高的比例组合有身长/头长比值(0.765)、体长/头长比值(0.732)、身长/体厚比值(0.703),均达到较强程度的相关,比单个性状的相关性有明显提高。结果表明,利用可量性状预测罗非鱼的出肉率是可行的。     

Stable isotope analysis to quantify contributions of supplementary feed in Nile Tilapia Oreochromis niloticus (GIFT strain) aquaculture

Nile tilapia (Oreochromis niloticus) is currently one of the most farmed freshwater fish and contributes significantly to total global aquaculture production. The genetically improved strain of O. niloticus (GIFT) was introduced to Papua New Guinea (PNG) in 1999 to improve food and income security. The high cost and low availability of commercial fish feed hinder the growth of GIFT farming in PNG. Stable carbon and nitrogen isotopes were used to determine the role of supplementary and natural food sources in the diet of GIFT in pond‐based aquaculture. Two treatments were used: treatment 1 was daily feeding, and treatment 2 was weekly feeding, each with three replicates. Isotopic analysis of muscle tissue and all potential food sources showed that pellet feed contributed 7% to the growth of GIFT in daily‐fed ponds and 33% in the weekly‐fed ponds. Highly enriched δ¹⁵N values for chicken manure, compared to depleted values for GIFT and other natural food sources in both treatments, clearly indicate insignificant contributions of this input to production. After 90 days of cultivation, the average final body weight of GIFT receiving daily feed inputs was 134 g (average 19 cm), while for weekly‐fed it was 92 g (17 cm). The feed conversion ratio (FCR) was poor (6.4:1) in the daily‐fed GIFT ponds compared to a better, and preferable, FCR (1:1) in the weekly‐fed ponds. The findings of this study show that pelleted feed was not the major contributor to the growth of GIFT. Genetically improved farmed tilapia aquaculture should focus on enhancing natural food availability for fish production.     

Genetic diversity and differentiation of Nile tilapia (Oreochromis niloticus) revealed by DNA microsatellites

To assess the genetic diversity of Nile tilapia Oreochromis niloticus, a total of 250 fish from five Egyptian populations were genotyped using six microsatellite markers. Heterozygosity and Wright's F‐statistics (F_IS, F_ST, and F_IT) were calculated to determine the genetic variation within and between these populations. Observed heterozygosities were in the range of 0.4 (Burullus) to 0.96 (Qena), with F_IS values ranging from 0.082 to 0.282. The mean F_ST showed that approximately 96.5% of the genetic variation was within‐population and 3.5% was among populations. Standard genetic distances were used to classify the five populations into two major groups. The deeper lotic river Nile populations of Assuit and Cairo formed one group and the shallow less lotic Delta lakes populations of Manzalla and Burullus formed the second group, with the upstream Nile Qena population being an outgroup. The findings from the current study help understanding of the broad‐scale population structuring of the Nile tilapia (O. niloticus) allowing the population groupings identified to act as potential sources of genetic variation. These populations could be included in future Marker‐Assisted‐Selection programs for economically desired production traits.     

投喂频率对尼罗系吉富罗非鱼幼鱼胃排空、生长性能和体组成的影响

通过胃排空试验与养殖试验研究了不同投喂频率对尼罗系吉富罗非鱼幼鱼的胃排空、生长性能以及体组成的影响.在试验开始时,观测尼罗系吉富罗非鱼幼鱼的胃内饲料排空情况,胃排空试验结果表明,胃排空率的最佳描述为平方根函数,胃内饲料在饱食投喂后15 h左右完全排空,达到投喂前水平,80％胃排空为9h,也就是投喂后大约9h恢复食欲.360尾试验鱼(初始体质量3.72 g)以不同的投喂频率(1d4次、1d3次、1d2次、2d4次、2d3次、2d2次)分组,每组设立3个平行组,随机养殖于18个网箱中,每箱养殖20尾鱼,按饱食量投饲膨化饲料.养殖期为6周.尼罗系吉富罗非鱼幼鱼在投喂频率为1d4次、1d3次和1d2次时特定生长率和饲料效率显著高于投喂频率为2d4次、2d3次和2d2次时(P＜0.05);投喂频率为1d2次、2d4次、2d3次和2d2次时其摄食量显著低于1d4次和1d3次时(P＜0.05).随着投喂频率降低,鱼体水分含量逐步上升,脂肪和蛋白质含量逐步下降,其中1d4次、1d3次组鱼与2d2次组鱼有显著性差异(P＜0.05).各投喂频率组间的肝体指数无显著性差异(P＞0.05).3.7～48.0 g尼罗系吉富罗非鱼幼鱼的适宜投喂频率为1d2次,较2d2次、2d3次和2d4次时明显提高了生长速度和饲料效率,较1d3次、1d4次摄食量显著降低.2种试验结果较为一致.     

Effect of dietary betaine levels on growth performance and hepatic intermediary metabolism of GIFT strain of Nile tilapia Oreochromis niloticus reared in freshwater

An 8‐week feeding experiment was conducted to determine the effect of dietary betaine levels on the growth performance and hepatic intermediary metabolism of genetically improved farmed tilapia (GIFT) strain of Nile tilapia Oreochromis niloticus (mean initial body weight: 78.3 ± 1.3 g, means ± SD). Six practical diets were formulated with the incorporation of betaine at the levels of 0 (control), 5, 10, 15, 20 and 25 g kg⁻¹. Survival showed no significant differences among the treatments (P > 0.05). The highest and lowest weight gain (WG) and specific growth rate (SGR) were observed for fish fed the diets containing 5 and 0 g kg⁻¹ (control) betaine, respectively. Feed intake showed similar trend with WG and SGR. In contrast, feed conversion ratio was the lowest when dietary betaine level was 5 g kg⁻¹. In general, dietary betaine supplementation showed no significant effect on hepatic composition of tilapia. Condition factor and viscerosomatic index tended to increase with increasing dietary betaine levels from 0 to 5 g kg⁻¹ and then decline when dietary betaine levels further increased from 5 to 25 g kg⁻¹. In contrast, hepatosomatic index declined with increasing dietary betaine levels (P < 0.05). Dietary betaine levels significantly influenced several hepatic enzymatic activities, including succinate dehydrogenase, lactate dehydrogenase, malic dehydrogenase, lipoprotein lipase and hepatic lipase, suggesting that dietary betaine addition had significant effects on nutrient metabolism in the liver. Based on the second‐order polynomial regression analysis of WG, 12.5 g kg⁻¹ of dietary betaine level seemed optimal for genetically improved farmed tilapia strain of O. niloticus.     

3种品系尼罗罗非鱼生长及高密度胁迫后生理响应变化的比较

以‘吉富’、‘新吉富’、‘埃及尼罗’3种不同品系尼罗罗非鱼(Oreochromis niloticus)为研究对象, 通过不同品系之间生长与高密度胁迫反应的比较, 探讨3种尼罗罗非鱼的生长特点与应激后生理响应的变化规律。将初始规格基本一致的3种品系尼罗罗非鱼饲养100 d后, 吉富罗非鱼特定生长率最高, 新吉富其次, 两者间无显著差异(P>0.05), 埃及尼罗罗非鱼特定生长率显著低于吉富罗非鱼(P<0.05)。吉富与新吉富罗非鱼的内脏比显著高于埃及尼罗(P<0.05); 3种尼罗罗非鱼的肥满度之间无显著差异(P>0.05)。养殖实验结束后, 进行48 h的急性高密度(100 g/L)应激实验。应激48 h内, 吉富与新吉富罗非鱼血清总蛋白、葡萄糖、谷草转氨酶、胆固醇与溶菌酶活力/水平以及肝HSP70mRNA水平呈先上升后下降的变化。应激48 h后, 埃及尼罗罗非鱼血清皮质醇水平与应激前相比无显著差异(P>0.05), 吉富与新吉富罗非鱼的皮质醇水平显著高于应激前(P<0.05); 埃及尼罗罗非鱼血清溶菌酶活力与肝HSP70 mRNA水平在应激后48 h内始终高于应激前(P<0.05)。研究结果表明, 短期高密度胁迫可提高3种尼罗罗非鱼血清葡萄糖与甘油三酯的利用, 并诱发肝损伤。埃及尼罗罗非鱼的抗高密度应激能力高于吉富和新吉富罗非鱼。

     

Comparative digestion efficiencies in conventional, genetically improved and genetically male Nile tilapia, Oreochromis niloticus (L.)

Apparent digestibility of dry matter, protein, lipid and energy of a fishmeal‐based feed (41% crude protein, 9% crude lipid and 19 kJ g⁻¹ gross energy) was compared in genetically improved farmed tilapia (GIFT), genetically male Nile tilapia (GMNT) and conventional Nile tilapia (CNT) (Oreochromis niloticus). The experimental fish were reared individually under standardized conditions in a recirculation system at 27±0.1°C for 10 weeks. Titanium dioxide (TiO₂) was used as a marker. Faeces of individual fish were collected daily by siphoning and stored at −18°C before analysis. No significant differences (P<0.05) were observed in the digestibility coefficients of feed dry matter (78.2±3.4%, 77.7±4.4% and 76.4±3.7%), protein (87.9±3.0%, 88.4±2.8% and 88.0±3.3%), lipid (90.0±2.5%, 91.0±2.1% and 89.4±3.0%) and energy (90.4±1.9%, 90.7±2.0% and 89.4±2.3%) in GIFT, GMNT and CNT respectively. At the end of the experiment, there were no significant differences (P<0.05) in average percentage growth (82.2±7.2, 87.3±7.7 and 74.7±4.1 respectively for GIFT, GMNT and CNT), growth rates or feed utilization efficiencies between the three tilapia groups. We conclude that the higher growth claimed for improved GIFT and GMNT as compared with CNT, if ever existing, cannot be attributed to higher nutrients or energy digestibility.     

Effects of four feeding stimulants in high plant‐based diets on feed intake,growth performance,serum biochemical parameters,digestive enzyme activities and appetite‐related genes expression of juvenile GIFT tilapia (Oreochromis sp.)

The present research evaluated the effects of four feeding stimulants on feed intake (FI), growth performance, body composition, serum biochemical parameters, digestive enzyme activities and appetite‐related gene expression for juvenile GIFT tilapia. Five experimental high plant‐based diets (with 0, 0.4 g kg^?1 dimethyl‐β‐propiothetin (DMPT), 0.6 g kg^?1 dimethylthetin (DMT), 1.8 g kg^?1 tryptophan (Trp) and 6 g kg^?1 betaine (Bet), respectively supplemented) were fed to juvenile GIFT tilapia (Oreochromis sp.) (3.34 ± 0.01 g) for 8 weeks. The results showed that FI was significantly increased by Trp and DMT. The highest specific growth rate (SGR) and protein efficiency ratio (PER) was observed for fish fed Bet diet, followed by DMT. Serum triglyceride was significantly increased by DMPT. Fish fed Bet diet showed significantly higher intestinal protease, liver protease and intestinal amylase activities. The neuropeptide Y (NPY) mRNA expression in brain was significantly improved by Trp, and ghrelin mRNA expression in stomach was significantly increased by DMT. It is concluded that supplementation of Trp or DMT could act as an effective feeding stimulants (FS) in high plant‐based diets for juvenile GIFT tilapia, which might be associated with the relatively higher orexigenic (NPY or ghrelin) genes expression, and supplementation of Bet could improve SGR, PER and reduce feed conversion ratio (FCR) of juvenile GIFT tilapia.     

Genetic diversity of Nile tilapia populations revealed by randomly amplified polymorphic DNA (RAPD)

Genetic diversity of the Nile tilapia Oreochromis niloticus collected from the river Nile (Cairo, Assuit and Qena) and two Delta lakes (Burullus and Manzalla) in Egypt was examined by the analysis of randomly amplified polymorphic DNA (RAPD). Of 25 primers examined,21 primers produced 230 RAPD bands. The percentage of polymorphic bands in Manzalla (29.4%) and Burullus (24%) populations was low compared with Assuit (30.54%), Cairo (33.5%) and Qena (44.84%) populations. The highest percentage of polymorphic bands was observed in the Qena population,suggesting a greater potential for use in breeding programs. The molecular phylogenetic tree constructed by unweighted pair‐group method of analysis shows Manzalla and Burullus populations strongly linked and separate from the Assuit and Cairo populations, with Qena population as outgroup. The data serve as a baseline analysis of the current genetic diversity found among O. niloticus populations in Egypt.     

饲料磷水平对吉富罗非鱼营养代谢和肠道微生物的影响

为研究饲料不同磷水平对吉富罗非鱼营养代谢及肠道微生物的影响,实验以磷酸二氢钙作为磷源,配制成总磷含量为0.26%(低磷组)、0.81%(适磷组)和1.51%(高磷组)的3组等氮等能饲料,每种饲料为一个处理,每个处理设置4个重复,每个重复30尾鱼,用3种饲料分别饲喂初始体重为(8.42±0.09) g的吉富罗非鱼8周。结果显示,适磷组吉富罗非鱼的增重率和特定生长率显著高于低磷组和高磷组,饲料系数在适磷组最低。脏体比、肝体比和肥满度随饲料磷水平的升高呈逐渐下降趋势。随着饲料磷水平的增加,吉富罗非鱼干物质、粗蛋白、粗脂肪、磷的表观消化率显著降低。对筛选到的差异代谢物进行KEGG注释和富集分析发现,饲料磷缺乏时下调的差异代谢物主要富集的代谢通路为氰胺酸代谢、葡萄糖酸酯的生物合成、丙氨酸、天冬氨酸和谷氨酸代谢,上调的差异代谢物主要富集的代谢通路为脂肪酸合成;当饲料磷过量时下调的差异代谢物主要富集代谢通路为精氨酸和脯氨酸代谢、苯丙酸的生物合成,上调的差异代谢物主要富集代谢通路为氨基糖和核苷酸糖的代谢。Ace、Chao1和Shannon指数表明,吉富罗非鱼肠道菌群丰度和多样性随着饲料磷水平的升高呈现...     

Assessment of the impact of dissemination of genetically improved Abbassa Nile tilapia strain (GIANT‐G9) versus commercial strains in some Egyptian governorates

WorldFish initiated a selective breeding program in Abbassa—Egypt to develop and produce the genetically improved Nile tilapia strain known as “Genetically Improved Abbassa Nile tilapia (GIANT)”, adopting the same technology used for the Genetically Improved Farmed Tilapia (GIFT), in Asia. WorldFish provided the Ninth Generation (G9) broodstock of the GIANT to 11 Broodstock Multiplication Centers (BMC’s) in five governorates; these centres then disseminated improved mixed‐sex fry to 160 tilapia hatcheries which supplied all‐male fry to 1,500 fish farms in 2017. We present results of an impact assessment of the G9 of GIANT in 83 of these fish farms in four Egyptian governorates (Kafr El‐Sheikh, Fayoum, Behera and Alexandria). Results indicate that the use of GIANT in all governorates achieved significantly higher (18.8%) fish yields (12.3%–26.4%) and 15.7% lower FCR (feed conversion ratio), reflecting a positive impact on their net profits compared with those who used commercial strains. Overall, fish farmers who stocked GIANT had significantly higher average fish sales (5,567 US$/ha) than those who stocked non‐improved commercial strains (5,192 US$/ha) in all governorates. However, when comparing within governorates, the difference was significant only in Fayoum and Alexandria noting a mixed performance of the GIANT strain. The mixed performance indicates that some hatcheries may have crossed the different strains, which lowered the performance differences. To get an objective analysis of the performance of the GIANT, it is recommended that similar assessment be undertaken with new generations of the strain supported by on‐farm performance trials.     

Spawning performance and seed production from hybridization between Oreochromis spilurus and the GIFT strain of the Nile tilapia Oreochromis niloticus

This study compared the spawning performance of four crosses between the salt‐tolerant tilapia Oreochromis spilurus and the fast‐growing genetically improved farmed tilapia (GIFT) strain of the Nile tilapia Oreochromis niloticus: (1) O. spilurus♀×O. spilurus♂ (SS); (2) Nile ♀× Nile ♂ (NN); (3) Nile ♀×O. spilurus♂ (NS) and (4) O. spilurus♀× Nile ♂ (SN). In each cross, males and females having mean weights of 157 and 115 g, respectively were stocked in 0.43 m³ tanks at a male to female ratio of 1:3. Seeds (unhatched eggs, yolk‐sac fry and free swimming fry) were harvested biweekly for 127 days. Viable spawns resulted from all crosses. The NN cross produced the highest total seeds tank^?1 (2890), seeds (kg female)^?1 day^?1 (48.3), seeds m^?2 day^?1 (23.3) and seeds female^?1 day^?1 (7.9), followed by the SS and SN crosses. The NS cross had the lowest fecundity. Lower spawning parameters in the NS and SN crosses may be attributed to the lower social compatibility between the males and females compared with that of the pure parents. The survival and growth of the offspring from the four crosses will be compared in seawater (37–40 g L^?1) to assess whether hybrid vigor was produced.     

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 Variability in Eight Cultured and Two Wild Populations of Japanese Flounder,Paralichthys olivaceus,Based on the Mitochondrial DNA Control Region

To examine the present population genetic diversity and variability of Japanese flounder, a 394‐bp hypervariable fragment of mtDNA control region was sequenced. A total of 215 individuals from two wild and eight cultured populations were analyzed. The 91 variable sites defined 61 haplotypes and 12 of them were shared. Six single base pair insertion/deletions were detected. The haplotype diversity (h), the nucleotide diversity (π), and mean number of pairwise differences (k) in cultured populations (h = 0.443–0.844; π = 0.010–0.030; k = 3.745–11.838) were obviously lower than those in the wild populations (h = 0.987–0.988; π = 0.032; k = 12.443–12.718). Fixation index (F_st) and analysis of molecular variance (AMOVA) revealed that significant genetic differentiation mainly existed among cultured populations. The results of the exact test of population differentiation (nondifferentiation exact P values) rejected a panmictic mtDNA gene pool in all cultured populations. The results of this study indicated that genetic diversity of cultured Japanese flounder populations in China had significantly declined due to farm propagation and an increase in broodstock number should increase genetic diversity in cultured Japanese flounder base on the genetic theory.