Genetic parameter estimates for growth‐related traits of blunt snout bream (Megalobrama amblycephala) using microsatellite‐based pedigree

Blunt snout bream (Megalobrama amblycephala) is an herbivorous freshwater fish species native to China and has been recognized as a main aquaculture species in the Chinese freshwater polyculture system with high economic value. The genetic parameter estimates for important economic traits are needed for its selective breeding. The aim of this study was to estimate the heritabilities for its growth‐related traits and explore the genetic and phenotypic correlations among the traits using microsatellite‐based pedigree approach. Offspring from a mass‐spawning of 92 broodstocks (42 sires and 50 dams) were reared in a communal pond and nine microsatellites were used to identify the parents of each sampled offspring. Of 749 offspring randomly selected, 708 (94.53%) could be assigned directly to a single parental pair, which was used for heritability estimates. Data were analysed using the method of restricted maximum likelihood (REML) using animal model and the results showed that the heritabilities of body weight, body length, total length and body height were 0.65, 0.53, 0.53 and 0.50, respectively. High genetic correlations were found among these four traits. According to these results, selection for growth seems to be feasible in M. amblycephala and the other growth traits will be heightened accordingly with the selection based on body length.     

Estimates of heritabilities and genetic correlations for growth and gonad traits in the sea urchin Strongylocentrotus intermedius

The present study is the first estimate for the sea urchin, Strongylocentrotus intermedius, of genetic parameters for growth and gonad traits during the entire reproductive period. 2165–5764 sea urchins were sampled from 74 to 120 families at six different growth stages. Six hundred individuals were sampled from 20 randomly chosen families at harvest. Coefficients of variation for most growth and gonad traits were high (18.08–78.66%) suggesting a good variation foundation for breeding. Point estimate for heritabilities based on the sire components of variance were moderate to high for test height (0.24–0.39), test diameter (0.21–0.48) and body weight (0.16–0.49). Heritabilities of gonad wet weight, gonad index and gonad moisture at harvest were 0.17, 0.41 and 0.50 respectively (moderate or high). Gonad colour parameters, L^* (lightness) and a^* (redness) have a heritability of 0, while b^* (yellowness) and colour difference ΔE₁ and ΔE₂ have very similar heritabilities of 0.2, 0.18 and 0.21 respectively. Heritabilities of β‐carotene concentration and content were 0.89 and 0.44 respectively. The genetic correlations between the two measured traits ranged from ?0.984 to 0.999. Gonad wet weight, L^*, b^*, β‐carotene concentration and β‐carotene content had significant positive genetic correlations with all the growth traits. However, gonad index, gonad moisture and colour differences ΔE₁ and ΔE₂ had significant negative genetic correlations with growth traits. The present study indicates that growth, gonad yield and most gonad quality traits could be improved by selection with moderate to high potential. Indirect selection should be applied on gonad traits using growth traits as secondary traits. The present study provides important theoretical guidance for future selective breeding programmes for S. intermedius.     

Genetic covariation in production traits of sub-adult black bream Acanthopagrus butcheri after grow-out

Predicting the suitability and reliability of traits associated with juvenile growth as indirect selection criteria for choosing future broodstock requires accurate and repeatable estimates of genetic (co)variation for growth traits at different ages. We compared juvenile wet weight of black bream Acanthopagrus butcheri (Munro) at 6 months of age with wet weight, dressed weight, fillet yield and gonad weight in tagged individuals at 18 months of age, following 12 months of farm grow‐out. Fish survival and tag retention was high, and there was significant among‐family variation for all traits. The phenotypic correlations among wet weight, dressed weight and fillet yield at 18 months of age were very high (0.93–0.97) and similar to their genetic correlations (0.96). Importantly, the phenotypic correlations between wet weight at 6 months and wet weight, dressed weight and fillet yield at 18 months were high (0.63–0.65), and so too were their genetic correlations (0.66–0.73), indicating the potential for using wet weight in the hatchery as a selection criterion for improved weight and meat yield of fish at harvest. Gonad weight shared little or no phenotypic or genetic correlation with these other traits, suggesting that selection for faster growing fish will not affect fecundity or sexual maturation rate. It appears, however, that cultured black bream do become sexually mature more rapidly than wild fish, as 78% of all fish harvested in this study had developing or mature gonads, whereas less than 50% of fish in wild populations are reproductively mature by the same age. Precocious sexual development may lead to uncontrolled spawning in grow‐out ponds and a potential loss of selection gains.     

Estimates of heritability and genetic correlations for growth‐related traits in the tiger prawn Penaeus monodon

Heritabilities and genetic and phenotypic correlations were estimated for body weight (BW), body length (BL), carapace length (CL), carapace width (CW) and carapace height (CH) of the Penaeus monodon from measurements on progeny at 6 months of age resulting from a nested mating design. Estimation was made on data from 41 full‐sib and 10 half‐sib families. The estimated heritabilities for these traits were 0.13–0.24, and the significantly phenotypic and genetic correlations were 0.81–0.94 and 0.88–1.00, respectively. The present results indicate that genetic improvement through selective breeding conducted on P. monodon might be feasible and would be an efficient method to obtain a positive response to selection.     

Dietary choline requirement for juvenile blunt snout bream,Megalobrama amblycephala

A 12‐week feeding trial was conducted to determine dietary choline requirement for juvenile Megalobrama amblycephala. The basal diet was formulated to contain 310 g kg^?1 diet from vitamin‐free casein and gelatine. Choline chloride was supplemented to the basal diet to formulate six purified diets containing 0, 250, 500, 1000, 2000 and 4000 mg kg^?1, respectively. Each diet was randomly fed to quadrupled groups of Megalobrama amblycephala with initial average weight 1.84 ± 0.04 g in a flow‐through system. Results showed weight gain was increased significantly with increasing dietary choline levels (P < 0.01). Lipid content of liver decreased significantly as dietary choline concentration increased (P < 0.01), whereas lipid content of dressed carcass showed opposite trend (P < 0.01), and lipid content of whole‐body was unaffected by dietary choline supplementation. Broken‐ line regression of weight gain, liver and muscle choline concentration showed choline requirements of Megalobrama amblycephala of 1198, 1525 and 1365 mg kg^?1, respectively. In addition, dietary choline supplementation significantly improved lipid content of dressed carcass but not the content of whole body of blunt snout bream.     

Relationships Among Total Weight, Body Shape, Visceral Components, and Fillet Traits in Palmetto Bass (Striped Bass Female Morone saxatilis× White Bass Male M. chrysops) and Paradise Bass (Striped Bass Female M. saxatilis× Yellow Bass Male M. mississippiensis)

Relationships among total weight (W), and linear measures of body shape, visceral component weights, and fillet weight (Y) in market-size (>454 g) palmetto bass (Morone saxatilis female ×M. chrysops male, N= 138) and paradise bass (M. saxatilis female ×M. mississippiensis male, N= 134) were determined with the allometric equation: Y = aW^b. Allometric analysis was used to compare traits of palmetto bass and paradise bass, and to identify factors influencing fillet yield. Paradise bass, an all female hybrid, had deeper, thicker, shorter bodies, and smaller heads than palmetto bass females. Male and female palmetto bass had similar body shapes. Values of growth coefficients (b) for body shape traits (range 0.21–0.48) indicated that shape was proportional across the weight range of fish used. Mean visceral fat and ovary weight were higher in paradise bass than in palmetto bass females suggesting the reproductive cycle was more advanced in paradise bass females. Whole fillet (skin and ribs intact) and skinless fillet (ribs intact) were larger for paradise bass than for palmetto bass, but trimmed fillet (skin and ribs removed) was not different between fish. Relative increases of whole and skinless fillet weights were greater than total weight in both groups indicating that the percentage of body mass attributed to fillet increases slightly as total weight increases. Therefore, small increases in fillet yield can be achieved by rearing fish to a larger size. Stepwise regression of whole, skinless, and trimmed fillet weight on body shape traits resulted in three parameter models with r²-values of 0.27–0.29 in palmetto bass, and of 0.37–0.43 in paradise bass. Addition of visceral components as independent variables in the models increased r²-values to 0.31–0.36 for palmetto bass and to 0.45–0.52 for paradise bass. Low phenotypic variation in fillet yield (CV = 3–5%) and poor predictability of yield from measures taken on live fish limit the potential for improving yield through individual selection. Identification of superior species or strain crosses or rearing fish to a larger size appear to be the best strategies for improving fillet yield of Morone hybrids.     

Phenotypic and genetic parameters for body traits in the giant freshwater prawn (Macrobrachium rosenbergii) in India

Phenotypic and genetic parameters were estimated for three body traits (harvest weight, carapace length and standard length) and for adult male morphotypes of the giant freshwater prawn Macrobrachium rosenbergii in a fully pedigreed synthetic population in India. The data set included 9,173 progeny produced over four generations from 162 sires and 234 dams. Variance components and genetic parameters were estimated fitting an animal model using the residual maximum‐likelihood methodology. The heritabilities for harvest body weight (HW), carapace length (CL) and standard length (SL) were moderate (0.22 ± 0.056, 0.22 ± 0.055 and 0.25 ± 0.059 respectively). The common environmental effects for HW, CL and SL were 0.10 ± 0.020, 0.08 ± 0.018 and 0.10 ± 0.021 respectively. As M. rosenbergii is sexually dimorphic, we estimated heritabilities within each sex. Heritability of HW in females (0.27 ± 0.068) was greater than that in males (0.15 ± 0.057). CL and SL followed the same pattern. The occurrence of male morphotypes is a unique characteristic of adult populations of M. rosenbergii. Populations from culture ponds exhibit a wide range of sizes. To examine whether there was a heritable component in male morphotype frequencies, we treated male morphotypes as traits. The additive genetic variance (and hence the heritability) was zero for male morphotype, indicating that selective breeding to increase the proportion of desirable male morphotypes would not be effective. The genetic correlations among body traits were all positive, high and approaching unity. The results are discussed in relation to selection plans for the giant freshwater prawn.     

Genetic parameters for growth‐related traits and survival with age in the Kuruma shrimp Marsupenaeus japonicus

Genetic parameters were estimated for growth‐related traits and survival of the Kuruma shrimp Marsupenaeus japonicus based on 66 families, including 30 paternal half‐sib families, which were obtained using artificial insemination of two females by each male. The variance components for growth‐related trait and survival were estimated using a single‐trait animal model and a sir‐dam model, respectively, and genetic parameters were estimated using the restricted maximum likelihood method. The coefficients of variation for growth‐related traits such as body length (BL), abdominal length (AL), and body weight (BW) were 9.36%–22.44%, 10.61%–21.92%, and 26.47%–58.33%, respectively, at different ages (45, 75, 105, 135, and 165 days). The corresponding heritability estimates for each growth trait were 0.1545–0.1951, 0.1672–0.1905, and 0.1596–0.1934, respectively, all of which were found to be at moderate levels and increased with age. The heritability of survival on day 165 was low (0.003). The genetic correlations among growth traits were positive and high (0.7316–0.9896) at the different ages, suggesting that selection to improve any single growth trait will cause positive responses in other growth traits examined in M. japonicus. The genetic correlations between growth traits and survival were also positive but low (0.005–0.087), which indicated that only selecting for growth traits may not cause a positive correlated response in the survival of the core population. According to the above results, we suggested that growth and survival traits should be taken as improving targets of breeding in M. japonicus. These results provided reference data for selective breeding and multitrait selection of M. japonicus.     

Genetic parameters of growth and resistance to Polydora ciliata in the pearl oyster Pinctada fucata

The pearl oyster Pinctada fucata is an economically important oyster cultured for pearl production in China. In this study, we used an animal model to estimate the variance components and genetic parameters of growth traits and a sire‐dam threshold model to estimate the resistance of P. fucata to polychaete Polydora ciliata. The results showed that the heritability estimates were 0.3850 ± 0.1421 for shell width, 0.3478 ± 0.1292 for body weight and 0.3387 ± 0.1316 for resistance to P. ciliata, and significantly different from zero (P < 0.05). Both phenotypic and genetic correlations were high between shell width and body weight (0.935 and 0.883 respectively) (P < 0.01), but low between resistance and shell width (0.260 and 0.233 respectively)/body weight (0.152 and 0.083 respectively) (r < 0.30; P > 0.05). The higher heritabilities for shell width, body weight and resistance traits suggested that the three traits can be genetically improved through selective breeding, but the low correlation between growth and resistance traits suggested that the resistance trait can be effectively improved through index selection or through hybridization of two specialized lines, i.e. a high‐resistant line and a high growth line.     

罗氏沼虾养殖群体表型性状间的相关性及类群差异分析

为研究罗氏沼虾(Macrobrachium rosenbergii)养殖群体表型性状间的相互关系及不同类群间的性状差异,本研究对人工养殖的罗氏沼虾雌、雄及“老头虾”3个类群共490个个体的体重、体长、全长等12个表型性状进行了相关分析、形态性状对体重影响的通径分析等。结果表明, 3个类群除上、下额刺数2个可数性状外,其他9个可量形态性状与体重都呈极显著的正相关(P<0.01);影响体重的关键形态性状在3个类群中各不相同,但体长、头胸甲长、第二步足长在3个类群中均是影响体重的关键指标;分别建立了各类群体重与关键形态性状的多元回归方程。聚类分析和主成分分析结果表明,雌、雄2个类群表型上更为相似,“老头虾”与雌性个体的差异最大。腹部轮廓特征(包括腹长、腹宽、腹高)、全长、体长及第二步足长对3个类群的差异贡献较大。雌性个体腹部发达,“老头虾”则第二步足尤为发达。本研究结果可为罗氏沼虾的选择育种、基础生物学及行业标准的制定提供数据资料。     

Estimates of genetic and phenotypic parameters for length and weight of marine net-pen reared coho salmon (Oncorhynchus kisutch Walbaum)

Heritabilities and genetic and phenotypic correlations were estimated for length and weight of two brood years (BY 1977 and BY 1978) of coho salmon [Oncorhynchus kisutch (Walbaum)] during the marine net-pen phase of rearing. The estimates were calculated from length and weight measurements on progeny resulting from a nested mating design and measurements at approximately 4 and 7 months after entering sea water. Point estimate for heritabilities based on the sire component for BY 1977 were low to moderate (0.02–0.19) and did not differ significantly from zero. On the other hand, BY 1978 estimates ranged from 0.31 to 0.62 and, with two exceptions, were significantly different from zero. The latter estimates may have been inflated by inclusion of variances from non-additive sources, but still indicated that differences in the genetic potential for increased growth between the two year classes may be substantial. Genetic correlations between length and weight within sampling periods were consistently high (0.95–1.00), indicating that pleiotropic gene action or close linkage among genes affects length and weight. Genetic correlations between body size traits (length and weight) between sampling periods varied considerably but suggested a potential for indirect selection gains. Genetic correlation approximations derived using family means or ranks appeared to provide reliable estimates and may be useful when environmental influences cause a significant deviation from normality.     

Estimation of genetic parameters for growth traits of Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> using an animal model

To estimate genetic parameters of growth traits in Japanese flounder Paralichthys olivaceus, full-sib and half-sib families were produced in three consecutive years at the Beidaihe Central Experiment Station in China. Each year 8–28 families were produced. The body weight, body length and body depth at 180, 240, and 360 days of age were measured for 5,224 individuals. Four animal models were used to examine the phenotypic variation of growth traits and were compared using the likelihood ratio test. The results showed that estimates for additive genetic effect heritabilities varied greatly depending on the model, trait and age. The maternal effect had a significant impact on phenotypic variation only for body depth at 180 days of age, which explained 49% of the phenotypic variance. The ratio of full-sib effect to phenotypic variation ranged from 0.09 to 0.22. Growth traits all exhibited low heritability (0.13–0.39), indicating that there is the potential for family selection breeding for these traits in Japanese flounder. Using the full model with the fixed, full-sib family, additive and maternal genetic effects, genetic correlations among the three traits for fish of the same age were estimated to be more than 0.80. Generally, the genetic correlations gradually increased as age increased.     

Estimation of genetic parameters for growth traits in cultured clam Meretrix meretrix (Bivalvia: Veneridae) using the Bayesian method based on Gibbs sampling

The aim of this study was to estimate the genetic parameters of the growth performance of clam Meretrix meretrix. As part of the breeding programme, 25 full‐sib families nested within eight half‐sib families were produced, planted out and tested to assess the heritability of the total body weight (TW), shell length (SL), shell height (SH) and shell width (SW) at different growth stages. Method of analysis was implemented using the Bayesian method based on the Multiple Trait using Gibbs Sampling under Animal Model program, which was used to estimate the (co)variance components of the traits and conduct genetic analysis. A total of 25 full‐sib families, each with 30–35 individuals within family, were used for the analysis. Significant positive genetic and phenotypic correlations between SL, SW, SH and TW with each other were observed. The growth traits showed high‐magnitude heritabilities, with values ranging from 0.64 to 0.85, which indicates that these traits should respond to selection and therefore should be included in genetic improvement programmes.     

Estimates of heritabilities and genetic correlations for body composition traits and G × E interactions, in gilthead seabream (Sparus auratus L.)

In this study, heritabilities for body composition traits, their genetic correlations with growth traits and the genotype–environment interaction (G × E) were estimated at 509 days (harvest size) for the first time in gilthead seabream (Sparus auratus L.), from the offspring in two different production systems (cages and tanks) in the Canary Islands. A total of 867 offspring from an industrial mass-spawning of 66 broodstocks were analysed. Parental assignment showed a total of 89 full-sib families (between 1 and 53 descendents per family) and was inferred using the RimA multiplex PCR designed by Navarro et al. (2008) [Navarro, A., Badilla, R., Zamorano, M.J., Pasamontes, V., Hildebrandt, S., Sánchez, J.J., Afonso, J.M., 2008. Development of two new microsatellite multiplex PCRs for three sparid species: gilthead seabream (Sparus auratus L.), red porgy (Pagrus pagrus L.) and redbanded seabream (P. auriga, Valenciennes, 1843) and their application to paternity studies. Aquaculture 285, 30–37.] with 100% success. The G × E interaction was analysed in 61 families present in the two environments and was null for visceral fat and it cannot be excluded for flesh composition traits. The heritability for visceral fat, expressed as a percentage of body weight, was 0.50 ± 0.07. The heritabilities for flesh composition traits, expressed as a percentage of fresh muscle weight, were 0.05 ± 0.03 for fat, 0.09 ± 0.03 for moisture, 0.08 ± 0.03 for ash and 0.02 ± 0.01 for collagen. Genetic and phenotypic correlations among body composition traits were mainly low–medium, except for moisture vs. muscular fat (− 0.98 and −0.61, respectively), moisture vs. collagen (0.85 and 0.45, respectively), collagen vs. muscular fat (− 0.80 and −0.35, respectively), and dressing percentage vs. visceral fat (− 0.92 and −0.51 respectively). Genetic correlations between body composition traits and growth traits were low for weight and length except with collagen for which they were high, and, in general, they were medium–high for condition factor. All these phenotypic correlations were low. These data suggest that selection through growth would improve flesh texture, but could decrease muscular fat in the long term. The latter trait could be improved by selection through moisture which is the flesh composition trait with the highest heritability and is the easiest to measure. The data also suggest that the inclusion of visceral fat percentage in a selection programme would thwart the negative effect of fat concentrated in the visceral cavity and increase the dressing percentage.     

Breeding for improved appearance of large rainbow trout in two production environments

A quantitative genetic analysis was performed to study potential to breed for improved body shape, skin colour and skin spottiness of large rainbow trout in sea and fresh water production environments, and in different stages of growth. The results showed that heritabilities in both production environments were moderate for body shape and skin colour and very high for skin spots. For body shape and skin spots, genetic correlation between the two production environments was high (r_A≥0.90), revealing weak genotype‐by‐environment interactions across the environments. For skin colour, genetic correlation between the environments was positive (0.78) but lower than for body shape and skin spots, indicating moderate genotype‐by‐environment interactions. Genetic correlations between 2‐ and 3‐year‐old fish were high for body shape and skin spots (r_A≥0.93) and moderate for skin colour (0.85), showing that differences among families persisted strongly during growth. The positive correlations between the environments and between the ages imply that selection in fresh water environment at a single point of time should lead to favourable correlated genetic responses in the sea and at the other stages of growth.     

Additive, dominance genetic effects for growth-related traits in common carp, Cyprinus carpio L.

Additive, dominance genetic effects were analysed for body weight (BW) and seven morphometric traits from three variants of red common carp, Cyprinus carpio var. singuonensis, C. carpio var. wuyuanensis and C. carpio var. color, based on a diallel cross‐mating design by using the additive–dominance genetic model. The results indicated that at 8 months of age (juvenile stage), the traits of pre‐dorsal height (PDH), pre‐dorsal width (PDW) and caudal peduncle height (CPH) were mainly controlled by additive effects; the traits of BW, total length (TL), standard length (SL), head length (HL) and caudal peduncle length (CPL) were mainly controlled by dominance effects. The narrow‐sense heritabilities of all traits ranged from 0.000 to 0.556; however, the broad‐sense heritabilities ranged from 0.453 to 0.775. At 20 months of age (adult stage), the traits of TL, SL, PDH and CPL were mainly controlled by additive effects, whereas the traits of BW, PDW, HL and CPH were mainly controlled by dominance effects. The narrow‐sense heritabilities of all traits ranged from 0.000 to 0.710; the broad‐sense heritabilities ranged from 0.629 to 0.934. Through the genetic merit prediction from three parents, it was found that the additive and dominance effects of C. carpio var. color could increase the BW and body length in their progeny, but these two genetic effects of C. carpio var. singuonensis and C. carpio var. wuyuanensis could decrease BW in their progeny. The genetic effects of C. carpio var. wuyuanensis could reduce total length, SL and caudal peduncle length, but increase body height in their progeny.     

Genetic effects on carcass-quality traits in hybrid striped bass (Morone chrysops♀×Morone saxatilis♂)

A 10 × 10 factorial mating design was used to examine the genetic effects on various carcass‐quality traits in hybrid striped bass (Morone chrysops♀×Morone saxatilis♂). A total of 448 offspring were raised in a ‘common‐garden’ environment and carcass‐quality traits were assessed at 389 days post fertilization; parentage of each fish was inferred from genotypes at 5–10 nuclear‐encoded microsatellites. There was a significant effect of dam and sire on body weight and fillet weight and a significant effect of dam on viscera weight and condition factor. When carcass‐quality traits were standardized to body weight, there was a significant effect of dam, sire and dam × sire interaction on viscera percentage (proportion of viscera weight to body weight). Phenotypic correlations between body weight and non‐standardized carcass‐quality traits were high (r_p=0.80–0.92), whereas phenotypic correlations between body weight and standardized carcass‐quality traits were low (r_p=0.13–0.19). Genetic correlations between body weight and fillet weight (dams and sires), and body weight and viscera weight (dams only) were significant and positive, while the genetic correlations between body weight and viscera percentage (dams and sires) were significant and negative. Significant general combining ability values for favourable carcass‐quality traits in the same breeder (dam or sire) occurred only in one or two of 20 (dams and sires) used in this study, suggesting that simultaneous improvement in multiple traits in hybrid striped bass may require evaluation of large numbers of candidate breeders. The effect of sex on body weight and all non‐standardized carcass‐quality traits was significant and appeared to be due to faster growth in females. These results indicate that selection for faster growth of hybrid striped bass would lead to a correlated increase in fillet weight and viscera weight but not necessarily to an increase in the proportion of fillet and waste product generated. The significant dam, sire and dam × sire interaction effects on viscera percentage and the negative genetic correlations between body weight and viscera percentage indicate that selection for reduced proportion of viscera relative to body weight might be feasible.     

Estimates of genetic parameters for growth-related traits of the red swamp crayfish,Procambarus clarkii

In this study, technologies of family construction and grow-out culture in the same pond were studied for red swamp crayfish. A total of 77, 110 and 78 families were constructed in 2011, 2012 and 2013, respectively. Heritability, genetic and phenotypic correlations were estimated for body weight, body length and carapace length through performance testing in progeny of 2012 at 5 and 10 months of age, resulting from a nested mating design. At 5 months of age, none of the estimated heritabilities were significant (0) based on sire components (h _s ² ) for these traits, the genotypic correlations, either; only the phenotypic correlations were significant (0.8561–0.9420). At 10 months of age, the estimated heritabilities (h _s ² ) were low for the three traits (0.1429–0.1632); the phenotypic and genetic correlations were significant, 0.8148–0.9052 and 0.9981–0.9993, respectively. It was concluded that genetic improvement through selective breeding conducted on red swamp crayfish might be feasible and would be an efficient method to obtain a positive response to selection for the 10-month-old red swamp crayfish.     

Phenotypic and genetic parameters of body size traits in Atlantic salmon Salmo Salar L.

Data on two year classes of Atlantic salmon, Salmo salar L., reared for 2 years in sea water, were analysed. Records were obtained on 1271 offspring of 58 sires and 171 dams mated hierarchically. Medium-high sire heritabilities (0.30-0.38) were found for ungutted and gutted body weights, body length, body circumference and condition factor (whole-body traits). Corresponding estimates for height and width of cutlet and average thickness of the abdominal wall ranged from 0.23 to 0.27. The latter measurements were made on a transversal section anterior to the dorsal fin. Heritability estimates derived from the dam component of variance corresponded in general to the sire estimates, indicating the absence of non-additive genetic and environmental effects common to full sibs. Estimated phenotypic and genetic correlations among the traits were all positive. With regard to the likely breeding goal of a commercial selection programme, the genetic correlations of ungutted and gutted body weights with condition factor (r_G=0.36-0.37) were judged unfavourable. The results revealed substantial impact of sex and sexual maturation status on growth. The need is stressed for proper adjustment for these effects when assessing growth or growth-related data.     

三角帆蚌紫色选育系1龄阶段内壳色及生长性状的遗传参数估计

采用群体选育辅助种内群体间杂交选育的方法,以内壳色、体质量作为选育性状,经过连续4代的选育获得了紫色选育系F4。本实验以F4为亲本进行繁殖,利用6对微卫星标记,对15个同批繁育的F4母蚌的1龄后代进行亲子鉴定,鉴别出了来自12个父本、15个母本的42个全同胞家系,使用ASREML软件的约束极大似然法对三角帆蚌内壳色及生长性状进行了遗传参数分析。结果显示,内壳色颜色参数L*、a*、b*、dE*的遗传力分别为0.31±0.22、0.11±0.08、0.36±0.18、0.29±0.19,L*、a*、b*之间的遗传相关和表型相关均较低,范围为0.08~0.47和0.04~0.32,L*与dE*相关性最大,遗传相关为-0.94±0.06,表型相关为-0.96±0.01;生长性状壳长、壳高、壳宽、体质量和壳重的遗传力分别为0.24±0.19、0.37±0.27、0.26±0.16、0.26±0.17、0.31±0.19,各性状间遗传相关和表型相关均为正相关,分别为0.71~0.92、0.66~0.94;颜色参数与生长性状的遗传相关和表型相关均很低,为0.02~0.18。三角帆蚌紫色选育系1龄阶段内壳色和生长性状的遗传力多为中高水平,对其继续进行遗传改良预期能够获得良好遗传进展。内壳色与生长性状的相关度很低,无法实现相互选择,体质量与其他生长性状相关均较紧密,表明将内壳色、体质量作为目标性状进行同步选育的方法合理,可实现同时改良壳色及生长性能的目的。