DNA markers for estimation of inbreeding depression and heterosis in the guppy Poecilia reticulata

Molecular markers have significant potential for use in precise breeding programmes in aquaculture. This paper reviews the use of DNA markers to estimate inbreeding depression and heterosis in the guppy Poecilia reticulata. Full‐sib matings revealed that inbreeding causes declines in survival and salinity tolerance, but not in undwarfism, growth and high water temperature tolerance, indicating the effects of inbreeding differ among fitness‐related traits. Salinity tolerance was used to quantify the level of inbreeding depression and heterosis because the trait is strongly sensitive to inbreeding and shows a linear decrease with an increase in inbreeding coefficient. A positive correlation was observed between heterozygosity at microsatellite loci and salinity tolerance among 17 guppy populations. This indicates that heterozygosity estimated from microsatellites is a useful indicator for the estimation of inbreeding depression, suggesting that overall heterozygosity is important for fitness‐related traits that show inbreeding depression. Use of DNA markers to estimate the amount of heterosis in various strain combinations was examined using diallele and reciprocal crosses among four domestic strains. The amount of heterosis differed among the strain combinations and correlated with Nei's genetic distance measured by microsatellites and also by dissimilarity using random amplified polymorphic DNA (RAPD) analysis. This indicates that microsatellite and RAPD markers are useful for estimating the amount of heterosis in various strain combinations, further suggesting that the amount of heterosis depends on the genetic differences between the strains. The present study showed that DNA markers are useful tools for estimating inbreeding depression and heterosis in guppy breeding.     

壳金长牡蛎自交和杂交家系生长与存活比较

选择具有生长优势的长牡蛎(Crassostrea gigas)G2(A)家系及具有明显生长和存活优势的G19(B)和G28(C)家系进行完全双列杂交,得到包括3个自交组(AA、BB、CC)和6个杂交组(AB、AC、BA、BC、CA、CB)共9个壳金长牡蛎实验组,分析各实验组在幼虫期及稚贝期不同日龄的各生长指标和存活性能,并评估了杂交组的杂种优势。结果表明,在整个培育阶段,大多数杂交组在不同生长时期均表现出较高的生长和存活性能,其中,浮游幼虫期5日龄,所有杂交组的壳高和壳长均显著大于自交组(P0.05);10日龄后,杂交组CB、BC和AC的壳高显著大于相应的自交组(P0.05),杂种优势明显;稚贝期85和130日龄,杂交组CB的壳高性能大于其他实验组。浮游幼虫期10日龄,CB组存活率显著大于AA、CA组(P0.05);稚贝期85日龄后,杂交组AC、CA和CB的存活率杂种优势逐渐增大;190日龄,杂交组AC、BC与自交组AA、CC之间存活率差异显著(P0.05)。研究结果为壳金长牡蛎新品种的培育及杂种优势的充分利用奠定了重要基础。     

三疣梭子蟹自交与杂交家系子一代生长和存活的比较

选择繁殖性能好的A家系(F6)和生长与存活好的B家系(F3),设计家系内自繁和家系间杂交,比较其自交组与杂交组子一代的生长与存活,评价杂交效应。由自交组F66(A♀×A♂)、F33(B♀×B♂)和杂交组F63(A♂×B♀)、F36(B♂×A♀)4个实验组组成,比较各实验组子一代在80、100、120、150日龄时的各生长指标杂种优势。研究表明,同一生长发育阶段的同一杂交群体的不同性状,表现的杂种优势大小有很大差异,而且同一杂交群体的同一性状在不同生长发育阶段表现的杂种优势大小同样有差异。自交组各阶段全甲宽、甲宽、甲长和体高的生长趋势比较一致,为F33F66;不同生长性状的生长速度方面,杂交组具有不同程度的总体杂种优势(-3.50%-19.47%)。结果显示,就存活而言,杂交组比自交组的存活率杂交优势明显,总体杂种优势率为24.8%,与存活相关的养殖产量的总体杂种优势率为15.99%,无论是生长性状还是存活,杂交使A家系获得的改良效果比B家系的好。A、B两个家系间存在的遗传差异获得杂种优势,是性状得到改良的基础。     

吉富罗非鱼与奥利亚罗非鱼自繁与杂交 F1遗传特性与抗病力分析

以吉富罗非鱼与奥利亚罗非鱼为繁育亲本,采用完全双列杂交繁育4组F1,将初始规格基本一致的4组罗非鱼饲养100 d后,运用“加性-显性”遗传分析模型,分析了4组F1罗非鱼8个生长相关性状杂种优势、遗传效应以及与性状间的相关性.结果表明:(1)F1群体平均优势为0.129 4～0.368 4.除尾柄长超亲优势较大外,其他性状的群体超亲优势较小或表现出负向超亲优势.(2)8个性状的广义遗传率(HB)为0.714 2～0.995 3,表明加性效应和显性效应对性状的遗传变异影响极显著(P＜0.01).除尾柄长外,其他性状的狭义遗传率(HN)介于0.469 4～0.737 9,表明加性遗传方差在表型方差中所占比率较高.(3)体质量、全长、体长、体高、体宽、头长、尾柄长、尾柄高性状之间表型相关在0.776 6～0.999 7范围内,而遗传相关在0.994 1～1.000 0之间,表明这些性状间都存在极显著的正相关.取样结束后,采用3.95×106 CFU/mL的海豚链球菌菌液进行腹腔感染,吉富罗非鱼自繁组F1代12 h后出现死亡,而奥利亚罗非鱼自繁组F1192 h后才出现死亡.384 h后,吉富罗非鱼自繁组F1死亡率为40％,正反交组F1分别为20％和23.3％,奥利亚罗非鱼自繁组F1死亡率最低,为6.67％.研究结果表明,除尾柄长外,杂交F1的其他性状不具备超亲优势,然而杂交可以提高选育后代的抗病力.     

Heritability estimates for processing and quality traits in common carp (Cyprinus carpio L.) using a molecular pedigree

Heritability estimates with a microsatellite parentage assignment based pedigree are of special interest in common carp cultured under traditional pond conditions. This method reduces common environment effects as all families can be grown immediately after hatching mixed in the same pond. We applied this method to study genetics of growth and processing traits in common carp at market size (1.5 kg and more). The experimental progeny was established by crossing 147 two-year old males and 8 females (six to eight-year old) of Hungarian synthetic mirror carp population. The fish grew up through three vegetation seasons and at the end a sample of 331 fish was examined for biometrical traits (standard length, body weight, relative head length, relative body height, relative body width), percent fat and processing traits (% processed body, % fillets with skin, % fillets without skin). It was shown that sex had a significant effect on most traits: females were larger and fatter than males, and they had both higher percent processed body and percent fillet with skin. Standard length, body weight, percent fat and relative head length had a high heritability (> 0.5), while relative body height, relative body width, percent processed body and fillet yields had a medium heritability (0.2–0.5). We found relatively high positive genetic correlations between body size (standard length and body weight) and percent fat (0.71 and 0.59, respectively), favourable genetic correlations between body size and percent processed body (0.69 for standard length and 0.74 for body weight) and between body size and fillet yields (0.50–0.77). Genetic correlations between body size and body shape (relative head length, relative body height and relative body width) were weak to moderate, thus selection for better growth should have little impact towards more rotund shape. Relative head length had strong negative correlation (− 0.7 to − 0.9) with percent fat, percent processed body and percent fillet yields. This means that indirect selection for reduced relative head length should be effective in improving of fillet yield.     

The effects of inbreeding on performance traits of adult Pacific oysters (Crassostrea gigas)

Understanding the effects of inbreeding is critical to the long-term viability of shellfish breeding programs, especially as breeders attempt to develop selected lines in hatcheries with small effective population sizes. Inbreeding depression in shellfish is well documented among the offspring of selfed individuals and full-sib crosses. This study was conducted to determine if crossing more distantly related parents would result in measurable inbreeding depression of performance traits in adult Crassostrea gigas raised in a commercial intertidal growing environment. Families were created with expected inbreeding coefficients (F) of 0, 0.0625, and 0.203. Average family yield, individual growth rate, and survival were recorded after the first and second growing seasons. Significant inbreeding depression in yield, individual growth rate and survival was observed after the first growing season in families with F=0.203 (P<0.0001), but not in families with F=0.0625 (P>0.058). After two growing seasons, significant inbreeding depression of yield and individual growth rate was observed in families with F=0.0625 (P<0.01) and F=0.203 (P<0.001). Significant depression of survival at harvest was observed only in families with F=0.203 (P=0.009). These results emphasize the importance of maintaining pedigree records in shellfish breeding programs to help avoid the deleterious effects of inbreeding depression, even among crosses of distantly related parents.     

近交对长牡蛎幼虫和稚贝生长与存活的影响

分别以2010年通过2个野生个体进行交配获得的A01全同胞家系和2011年通过A01家系子代进行交配获得A02全同胞家系为亲本,在2013年6月采用同时建立全同胞交配子一代F1(F=0.250)、全同胞交配子二代F2(F=0.375)及设置对照组(F=0)的方法,研究在相同环境条件下,不同实验组的受精率与孵化率以及近交对长牡蛎幼虫期、稚贝期生长和存活的影响,并初步探讨近交代数与近交衰退的关系。结果发现,各组的受精率均在90%以上,除F2组外其余2组的孵化率也在90%以上;幼虫阶段,F1组和F2组的壳高与壳长均从12日龄出现衰退(近交衰退系数,inbreeding depression coefficient,IDC0),且F2组壳高的近交衰退系数均小于同日龄F1组壳高的近交衰退系数;F1组和F2组的存活率在整个幼虫期间均出现衰退,且F1组和F2组存活率的近交衰退系数均随着幼虫日龄的增加而逐渐减小。稚贝阶段,F1组和F2组的平均壳高在各日龄均表现出近交衰退(IDC0),且F2组壳高的近交衰退系数均小于相同日龄F1组壳高的近交衰退系数;3个实验组的平均壳长在整个稚贝阶段无显著性差异;F1组和F2组存活率的衰退在不同日龄始终存在(IDC0),且随着稚贝日龄的增加其衰退程度逐渐加大。研究结果为长牡蛎选择育种和遗传改良提供了基础资料。     

Growth and survival of three small abalone Haliotis diversicolor populations and their reciprocal crosses

The aquaculture industry of small abalone Haliotis diversicolor in southern China is now close to collapse because of high mortality at the grow-out stage. To examine if survival and growth (shell length increase) could be improved by cross breeding among populations, a 3 × 3 complete diallel cross was conducted among three populations from Japan (A), Taiwan (B) and Vietnam (C). Performances in growth rate and survival at early juvenile, later juvenile and grow-out stages were compared among the six reciprocal cross lines and three parental lines. Magnitude of heterosis for survival and growth varied among cross lines in the three growing stages. As to mid-parent heterosis, H _AB was significantly ( P <0.01) higher than H _AC and H _BC at all three growing stages for both growth and survival, and all mid-parent heterosis fell between the two corresponding single-parent heterosis. H _AB was 6.84% for shell length and 69.09% for survival at Day 420. Our results of high survival heterosis in line AB and line BA show that crossbreeding between different populations can benefit the small abalone breeding programs and the industry.     

Inbreeding depression traits in pacific abalone Haliotis discus hannai by factorial mating experiments

ABSTRACT:   'Inbreeding depression' may be an avoidable phenomenon for abalone culture. However, only a few studies have been carried out on inbreeding depression. In the present study, using six families produced in 1994, a factorial mating system including inbreeding and outbreeding was constructed in order to demonstrate inbreeding depression traits of the Pacific abalone. In total, 24 inbreeding and 21 outbreeding crosses were produced during three years (1999–2001) and these offspring were reared for approximately one year. Significant differences in fertilization rate and growth were not observed between inbreeding and outbreeding crosses. However, the deformity rate of veliger larvae was always higher in inbreeding crosses than that of outbreeding crosses in all experiments. Moreover, a significantly high deformity rate was observed in some full-sib families of inbreeding. Alternatively, the survival rates of inbreeding crosses were much lower than for outbreeding crosses after about 4 months and one year in two rearing localities. These results indicate that inbreeding depression is observed in the traits of deformity rate and survival, but not in fertilization rate nor growth in the first generation of a full-sib family of the Pacific abalone.     

不同近交系数蛤仔橙色品系的生长和成活研究

以不同遗传背景的蛤仔（Ruditapes philippinarum）橙色品系为材料,采用建立半同胞家系子一代H1（F=0.125）、全同胞家系子一代F1（F=0.250）、全同胞家系子四代F4（F=0.594）及自然对照组C1（F=0）的方法,进行了不同近交系数蛤仔橙色品系生长和成活的研究.结果表明,在整个养殖周期中F1组的壳长生长最慢,在稚贝期和养成期均显著小于F4和C1组（P＜0.05）,H1、F4和C1组之间的壳长生长差异不显著（P＞0.05）.C1组的成活率在整个养殖周期中为最小,除幼虫期3日龄外,其他各日龄均显著小于其他试验组（P＜0.05）,而H1、F1和F4组之间的成活率则差异不显著（P＞0.05）.试验组F1壳长生长的衰退率为2.92％ ～ 18.33％,平均值为（12.05±6.54）％,试验组H1在稚贝期、养成期显现出一定的衰退现象,而试验组F4在整个养殖周期中均未表现出近交衰退现象;各试验组的成活性状在各日龄均未出现近交衰退.该研究为橙色品系的选育奠定一定的理论基础.     

Salinity tolerance of cultured Eurasian perch, Perca fluviatilis L.: Effects on growth and on survival as a function of temperature

Eurasian perch is generally only considered to be a candidate for freshwater aquaculture even though wild populations are found in estuarine and brackish water habitats. Little knowledge exists on two issues a) the effect of temperature on the salinity tolerance of perch and b) the long-term effects of brackish water on their overall growth performance. The present study addresses these two questions.

Firstly, the effect of temperature (12, 15, 20 and 25°C) on perch survival of a salinity challenge at either 13 or 18‰ was determined. Survival was unaffected by 13‰ at the two lowest temperatures whereas higher temperature and higher salinities had a dramatic detrimental effect (at 25°C, 50% mortality was reach at 62h and 39h for 13‰ and 18‰, respectively). Secondly, we examined the effect of salinity on growth, which was assessed by measuring standard length and body weight at regular intervals for 130days. In addition, Specific growth rate (SGR), Fulton's condition factor (K) and food conversion ratio (FCR) were also calculated as was the effect of salinity on plasma osmolality, blood ion content (Na⁺, Cl⁻, K⁺) and muscle water content at the termination of the experiment. The optimum growth for this study was seen in the lowest salinities at 0 and 4‰. Surprisingly, even small increases in salinity were detrimental to perch growth. At 10‰, growth in terms of body weight was reduced by about 50% after 130days compared to perch reared in freshwater.

Interest in brackish water production of perch would be most likely served best by selecting a strain of perch that is adapted to saline conditions, as found in the lower Baltic region. Further studies are required to understand the potential for brackish water perch production.     

凡纳滨对虾选育群体与近交群体、引进群体生长和存活性能比较

为研究凡纳滨对虾选育群体与近交群体、引进群体的生长和存活性能差异,本实验利用家系标准化构建方法构建了选育群体、引进群体和近交群体家系,开展共同养殖环境下的生长和存活性能测试实验,分析了三个群体的体质量、存活率和近交衰退情况.结果表明,选育群体收获体质量与引进群体、全同胞近交一代群体体质量均存在显著差异(P＜0.05),第60天收获时,选育群体比引进群体的体质量提高7.11％,比近交群体的体质量提高20.01％;选育群体和引进群体内不同家系生长速度存在较大差异,选育群体中增重最快的家系为6012家系,绝对增重率为0.29 g/d,比所有家系绝对增重率均值高31.82％,比增重最慢的家系高61.11％,引进群体中绝对增重率和特定生长率均最高的家系为6008家系,分别为0.33 g/d和3.17％/d,比所有家系均值分别高65％和33.19％,比增重最慢的家系分别高230％和128.06％;存活率方面,选育群体与引进群体差异不显著(P＞0.05),但与近交群体存在显著性差异(P＜0.05),存活率提高12.74％.近交衰退结果显示,与选育群体及引进群体相比较,近交群体收获体质量生长性状的实际衰退百分比分别为16.68％和10.76％,近交系数每增加10％所引起的近交衰退系数分别为-6.60％和-4.30％,且选育群体与近交群体在收获体质量上差异显著(P＜0.05);存活率性状也出现了一定程度的近交衰退,实际衰退百分比分别为11.30％和10.54％.本研究结果可为凡纳滨对虾的后期选择育种工作提供数据参考.     

Some effects of temperature and salinity on laboratory-reared eggs and larvae of Polydactylus sexfilis (Pisces: Polynemidae)

Effects of temperature and salinity on eggs and yolksac larvae of Polydactylus sexfilis (Cuvier and Valenciennes) were examined in laboratory experiments. Data on developmental rates as influenced by temperature are presented. Larval length at 95% yolksac absorption was maximized between 23.8 and 28.6°C. Based on the development of functional eyes and jaws, larvae were judged capable of feeding before the yolk was completely absorbed. Larvae incubated at intermediate temperatures also had larger amounts of yolk remaining when eyes and jaws were judged functional. Temperature and salinity effects on hatching success, survival at the end of the yolksac stage, and morphological abnormalities were studied in a 10 × 5 (temperature × salinity) array of treatments. In 34‰ sea water, normalized larval survival at the end of the yolksac stage was greater than 50% between temperatures of 21.9 and 28.0°C. Larval survival decreased at lower temperatures and salinities. Proportions of abnormal larvae increased at temperature and salinity extremes, and normal development was maximized between 26 and 34‰. Larvae (74 h after fertilization) were more tolerant to extreme high temperatures than were newly fertilized eggs. Upper salinity tolerance limits of 42-h larvae were greater at 26.2°C than at 23.5 or 29.2°C, and lower salinity was less tolerated at the two extreme temperatures. Based on the results, recommended temperatures and salinities for rearing P. sexfilis eggs and early larvae are 24–28°C and 26–34‰.     

Salinity tolerance of Nile tilapia fry (Oreochromis niloticus), spawned and hatched at various salinities

Fertilized eggs of the Nile tilapia (Oreochromis niloticus L.) spawned in freshwater, were removed from mouthbrooding females, 1 day post-spawning and artificially incubated at elevated salinities. At 6 days post-hatching, mean survivals of 85.5, 84.4, 82.5, 56.3, 37.9, 20.0 and 0% were recorded for broods incubated at salinities of 0, 5, 10, 15, 20, 25 and 32 ppt, respectively. Fertilized eggs exhibited a 96-h median lethal salinity (MLS-96) of 18.9 ppt, a value identical to that of 7- to 120-day-old fry and fingerlings. Fertilized eggs exhibited a higher median survival time (ST₅₀ = 978 min) than 7- to 395-day-old fry and fingerlings (ST₅₀ = 28.8–179.0 min).The salinity tolerances of fry spawned at various salinities and fry spawned in freshwater but hatched at various salinities, were determined using the median survival time (ST₅₀), mean survival time (MST) and 96 h-median lethal salinity (MLS-96) indices. For comparative purposes, fry spawned and hatched in freshwater were acclimatized to various salinities and their salinity tolerance determined. Fry salinity tolerance progressively increased with increasing salinity of spawning, hatching, or acclimatization. However, at equivalent salinity, early exposure (spawning) produced progeny of comparatively higher salinity tolerance than those spawned in freshwater and hatched at elevated salinity. Similarly, at equivalent salinity, progeny spawned in freshwater but hatched at elevated salinity exhibited higher salinity tolerance than those spawned and hatched in freshwater, then acclimatized to an elevated salinity.The utility of these methods of early salinity exposure toward the saltwater culture of tilapias is discussed.     

A simple test to estimate the salinity resistance of fish with specific application to O. niloticus and S. melanotheron

In order to develop a simple and accurate index of the salinity resistance of tilapia, batches of 10 juveniles (5 to 20 g) of two different species Oreochromis niloticus and Sarotherodon melanotheron reared in freshwater were subjected to gradual increases in salinity until 100% mortality. Seven daily increments of salinity were tested with 4 replicates: 2, 4, 6, 8, 10, 12 and 14 g l⁻¹ day⁻¹, while control batches were kept in fresh water. The temperature was maintained at 27 °C. The concentration of oxygen, ammonia and the pH were not limiting factors. The mortality, monitored on a daily basis, appeared after 2–51 days and was spread out over 1–20 days, depending on the increment of salinity. The higher the daily rate in salinity increase, then the shorter the time lapse before total mortality occurred. The cumulative mortality as a function of salinity fit well with simple linear regressions. The criterion of the resistance to salinity was the index MLS (median lethal salinity) defined at each daily rate as the salinity at which 50% of fish died. For S. melanotheron, the mean MLS was 123.7±3.5 g l⁻¹ whatever the daily rate in salinity. For O. niloticus, the MLS was 46.3±3.4 g l⁻¹ for daily increases in salinity ranging from 2 to 8 g l⁻¹ day⁻¹ and decreased significantly (P<0.05) above this level. The MLS-8 g l⁻¹ day⁻¹ ,which takes into account the full capacity of the fish to adapt to the increasing salinity, appeared to be a simple, optimized and efficient criterion for assessing the resistance to salinity for O. niloticus and S. melanotheron. This criterion can be a useful tool for ranking the different parental strains and hybrids of different genus and species of tilapia used in programmes of genetic selection for growth and salinity tolerance.     

Ontogenetic variability of chill tolerance in larval Artemia salina: I. Single type cryoprotectants

Chill tolerance was determined for various larval stages of Artemia salina with and without the addition of single cryoprotective agents (glycerol, glucose, sucrose and dimethylsulfoxide). Synchronous cultures of larvae were removed from the batch culture at post-hatch intervals (0, 3, 6, 12 and 24 h) and instantaneously exposed to solutions at −1°C for 10, 30 or 90 min intervals. Survival of larvae placed in freezing solutions without cryoprotectant (control group) varied with larval age. In zero-hour post-hatch controls larval survival decreased linearily with increasing exposure time. Each older stage (control group), however, was insensitive to the duration of −1°C exposure. The addition of cryoprotectant to the chilled solutions radically modified survival patterns and yielded results dependent on age, cryoprotectant concentration, and exposure time. Survival in cryoprotectant solutions sometimes exceeded 200% of survival in control solutions. Three hour post-hatch specimens were generally most tolerant to chilling in cryoprotectant solutions, while 12 h nauplii were least tolerant. The significance of these results for the development of cryogenic larval banking techniques is discussed.     

Effect of starvation on the growth and survival of post-larval abalone (Haliotis iris)

The starvation tolerance of post-larval abalone (Haliotis iris) was determined by examining post-larval growth and survival after various periods of starvation. Competent larvae (10 days old at 16°C) were induced to attach and metamorphose with 2 μM GABA. Post-larvae were either fed diatoms (Nitzschia longissima) or starved. In Experiment 1, post-larvae were starved immediately after metamorphosis for periods of 1, 2, 4, 8, 15, 20, 25 and 30 days. Starved post-larvae grew relatively well for several days after metamorphosis despite the absence of food (averages of 10.4 and 17.8 μm shell length (SL) per day after 8 days for two batches). Subsequent growth was minimal, averaging 1.7 and 0.7 μm day⁻¹ over 6–7 days for the two batches. There was no clear relationship between period of starvation and growth rate when fed. Mean daily growth rate over 3 weeks when fed ranged from 15–22 μm day⁻¹. However, the duration of starvation did have a significant effect on survival. Survival of post-larvae fed after 1–2 days of starvation was 90–100% after 3 weeks of feeding. Longer starvation periods gave progressively lower survival and post-larvae starved for 30 days all died within a week of being fed. In Experiment 2, post larvae were fed for 3 weeks after metamorphosis, then starved for 0, 3, 7, 14 or 21 days. Growth rates of starved post-larvae averaged only 5–6 μm day⁻¹ in the first week (vs. 30 μm day⁻¹ in controls), and later declined to zero. Growth resumed within a week following return to food, but the 14- and 21-day starvation treatments took 2 weeks to reach growth rates comparable to controls. The no-starvation controls and the 3- and 7-day starvation treatments all had >70% survival over 4 weeks after return to food. Survival in the 14- and 21-day starvation treatments was 15–20%, with almost all mortalities occurring in the first week after return to food. These data suggest that Haliotis iris post-larvae are relatively tolerant of starvation, so abalone farmers have a week or so to remedy food shortages before major post-larval mortality begins.     

魁蚶中国与韩国群体杂交子一代生长比较

开展魁蚶中国群体和韩国群体的正反杂交试验,建立了中国群体♀×韩国群体♂(中韩正交群体)、中国群体♀×中国群体♂(中国群体)、韩国群体♀×中国群体♂(中韩反交群体)、韩国群体♀×韩国群体♂(韩国群体)4个群体。稚贝出池后在海区(N 35°32′41.85″,E 119°41′29.49″)常规笼养,分别在4、5、7、9、11、13月龄取样,分析其生长、存活及杂种优势。研究结果显示,中韩正交群体壳长、壳高、壳宽和湿质量的杂种优势变化趋势一致:前期杂种优势率随着日龄的增长而持续增大,到11月龄时最高,13月龄又明显下降。11月龄壳长、壳高、壳宽和湿质量的杂种优势率分别为7.73%、4.80%、8.84%和27.44%,其中湿质量的杂种优势最为显著;中韩反交群体4个性状在7月龄和11月龄的杂种优势率基本为正值,最高值为2.61%。中韩正交群体和中韩反交群体存活率的杂交优势率均为正值,分别为5.89%和4.15%,中韩正交群体杂交优势略高于中韩反交群体。综合分析表明,中韩正交群体在生长性状和存活率上存在明显的杂种优势,是一种理想的育种材料。研究结果可为魁蚶种质资源的开发利用和杂交育种提供理论支撑和技术参考。     

Inbreeding evaluation using microsatellite and its effect on growth traits in turbot,Scophthalmus maximus

Turbot is an economically relevant fish, and simultaneously at the risk of inbreeding depression in China. Microsatellite DNA markers were used to evaluate inbreeding level of a random turbot breeding population and further investigate its effects on growth traits. DNA based inbreeding coefficients (F_DNA) were ranged from 0 to 0.4124. Average inbreeding coefficient was 0.0621 with a standard deviation of 0.0658. Regression analysis results showed inbreeding had a very significant (p < .01) effect on harvest body weight (BW) and significant (p < .05) effect on harvest body long (BL). Inbreeding depression, expressed as the percent change in phenotype per 10% increase in F, was ?4.00% for BW and ?1.14% for BL. The inbreeding depression on high inbreeding coefficient (more than 10%) individuals was further analyzed. A set of significant (p < .05) and larger inbreeding depression was obtained, ?7.15% and ?2.49% for BW and BL respectively. This study demonstrates that inbreeding has a negative effect on growth traits and highlights the need of DNA markers to control inbreeding and maximize the genetic diversity in selection breeding programs.     

太平洋牡蛎与葡萄牙牡蛎两亚种间杂交及其早期阶段生长与存活的杂种优势

利用山东青岛养殖的太平洋牡蛎(N)与汕头本地养殖的葡萄牙牡蛎(S)两个近缘种为亲本,采用正交设计建立了杂种组NS(N♂×S♀)和SN(S♂×N♀)与纯种组NN(N♂×N♀)和SS(S♂×S♀)4个不同的遗传组合,通过比较不同阶段(幼虫期、稚贝期、养成阶段)的生长和存活数据,研究了牡蛎近缘种间的杂种优势,目的为改良牡蛎的生产性状。结果表明,这两个近缘种之间杂交能够产生显著的杂种优势,杂交后代的生长与存活两个表型性状都得到改良。杂交组比近交组生长得快,杂种优势在幼虫期为37.44%,稚贝期为42.47%。杂交组也比近交组存活率高,8日龄幼虫存活率的杂种优势为76.80%、14日龄幼虫存活率的杂种优势可达107.70%,60、90和105日龄稚贝存活率的杂种优势分别为17.30%、15.62%和9.08%。研究表明,通过太平洋牡蛎和葡萄牙牡蛎两个近缘种间的杂交有望解决牡蛎养殖产业存在的育苗难、存活率低、生长慢、个体小等问题。