Abstract:Seed industry is the foundation of agricultural development, and a flourishing seed industry is the core element to ensure national food security, as well as an important measure to ensure national security. The development of seed industry involves many factors such as policies, technology and market. The development of aquatic genetic breeding technology in China is progressing with each passing day, but there is still a gap when compared to requirements put forward in the action plan for the revitalization of the seed industry. This paper expounds the current situation of aquatic genetic breeding technology in China from the perspectives of the research, development and application of breeding technologies, and analyzes the shortcomings of of aquatic breeding technology in China in terms of genetic resources protection and utilization, breeding technology innovation, breeding production system construction and monitoring and management of juveniles. Overall, the supply of juveniles is sufficient and the risks are manageable, but there are three main problems: the domestic genetic resources are rich but the genetic improvement rate is not high, the scientific research and breeding achievements are many but the transformation efficiency is not high, and the seed industry enterprises are many but the core competitiveness is not strong. In view of the short board, this paper puts forward some suggestions, such as strengthening the research of genetic resources mining and conservation and innovative utilization technology, strengthening the research and application of modern breeding technology, especially the creation and application of new genetic resources, strengthening the application of production system technology standardization, strengthening the research of breeding technology commercialization application, and strengthening the technical support for seed industry market supervision, so as to provide reference for the research direction of aquatic breeding technology innovation and the formulation of seed industry development policies in China.

Abstract:Genome editing breeding is a powerful technique in aquaculture organisms. China has made a big progress in genome editing researches and breeding in fish during last 10 years. The present paper is the first systematic review of the status, problems and prospect of fish genome editing breeding in China. Firstly, the authors gave a brief introduction to advantages and disadvantages of three genome editing technologies including Zinc Finger Nucleases(ZFN), Transcription Activator-Like Effector Nucleases(TALEN)and Clustered Regularly Interspaced Short Palindromic Repeats CRISPR-Associated(CRISPR/Cas9). Secondly, the definition and workflow of genome editing breeding in fish was proposed. Thirdly, the authors gave a detail introduction to the progress in genome editing breeding in fish in China. In brief, Chinese scientists have carried out genome editing in several important cultured fish such as tilapia, carp, crucian carp, half-smooth tongue sole, southern catfish et al. Especially, a variety of tilapia with sex-reversed female and with different color were generated by means of TALEN and CRISPR/Cas9 method. Also, dmrt1-mutated F₃ males with fast growth speed similar to females were generated by TALEN method in Chinese tongue sole. Crucian carp and blunt snout bream with less or no inter muscular bones were obtained. These genome edited fish can mature and spawn. The progress has brought China's fish genome editing breeding from following-up in the past to the present coexistence of following, running side-by-side, and even leading in some fish species. Finally, the authors summarized the current shortcomings and problems in fish genome editing breeding and prospected the future development direction of genome editing breeding in China, and proposed research focuses in fish genome editing breeding. The paper will have important role and significance for fish genome editing breeding in China.

Abstract:Along with the rapid and sustained increases of global aquaculture production, aquaculture has been rapidly replacing the capture fisheries in the last two decades, and already become a production activity with great potential to meet human demand for high-quality proteins. The rapid consumption growth of aquatic products in the world in recent decades shows the increasingly important role of aquatic products in the human food system. Genetic improvement has attracted much attention as a key part in the development of aquaculture. Up to now, selective breeding and cross-breeding are the main breeding methods, and economic traits such as growth rate and survival rate are the main target traits for improvement, which have played a fundamental, leading and strategic role in the development of the world aquaculture industry. Following the increasing demand for high-quality protein and the widespread popularization of the concept of the "Greater Food" approach, it is a general trend to make aquatic production into a more efficient food production system. Globally, however, the aquaculture seeds industry has some limitations, such as not many strains and species of genetic improvement, and improved traits lagging behind the needs of industrial development. It is necessary to improve technological, variety and mechanism innovation, to promote the development of high-quality aquaculture seed industry. Based on previous research results and various fishery statistics, this study summarizes the development of the global aquaculture industry, the genetic improvement of important aquaculture species, the application of breeding technology in aquaculture, the improvement of target traits, and the production data of six major species experiencing artificially genetic improvement to analyze the development status and existing problems, which could provide a reference for the study of the aquacultural seed industry as well as its high-quality development.

Abstract:The aquatic breeding is the basis for the development of aquaculture, serving as a strategic and fundamental core industry of fisheries, and essential for sustainable, healthy and environmentally friendly aquaculture development. With the development of globalization and marketization of the aquaculture industry, China's aquaculture seed industry is facing unprecedented opportunities and challenges. Along with rapid development of biotechnologies, aquaculture genetic breeding has transformed from traditional selection breeding and hybrid breeding to cell engineering breeding, marker-assisted selection breeding, genome-wide genotyping-based selective breeding, molecular design breeding and genome editing breeding. Advances in basic research and biotechnology of aquaculture genetic breeding have promoted the development of aquaculture seed industry in China. Till 2022, 266 newly bred aquaculture varieties were approved by the National Certification Committee for Aquatic Varieties and announced by the Ministry of Agriculture and Rural Affairs of China. Among them, common carp (Cyprinus carpio) occupies the top position with 31 new varieties, indicating great achievements in common carp breeding. In this paper, the current status of common carp breeding in China is summarized, along with its germplasm and genomic resources. Additionally, the foundation of molecular breeding is briefly reviewed, along with the research status of its utilization in common carp growth, disease resistance, body color differentiation, feed conversion ratio and other economic traits. Finally, the development direction and measures of the common carp breeding industry in the new era are proposed, with the purpose of improving fish breeding in China.

Abstract:Aquatic products have become the third most important source of food protein after cereals and milk all over the world. Fifteen percent of food protein intake for a global population of 7 billion people originates from aquatic products. In China, the largest production and consumption country in the word, aquatic products meet 30% of animal protein demand for its people. It is a global scientific goal to maintain the sustainable and stable supply of aquatic products, where aquaculture genetic breeding plays an important role. Aquaculture breeding is a research hot spot in which countries all over the world compete for development. The development of breeding technology and the cultivation of fine varieties fully reflect comprehensive innovation strength and market competitiveness of the country. Since the 1950s, artificial spawning, insemination and hatching of silver carp (Hypophthalmichthys molitrix) and bighead (Aristichthys nobilis) were realized, which marked China taking the leading role in the technology and theory of artificial propagation of freshwater fish in the world. After that, China's aquaculture breeding has achieved great achievements in scientific research and made irreplaceable contribution to the development of the industry. Carrying out genetic breeding research on aquaculture species can improve the intensity of germplasm resources development and the depth of gene resources mining, exploit the scientific and technological potential of China’s aquaculture seed industry, and enhance the level of industrial application. Aquatic breeding in China covers two major systems, namely, the breeding and promotion of new varieties, which has become the top priority to promote the green development of the aquaculture industry. It has demonstrated outstanding effectiveness in ensuring stable and high-quality protein supply, enhancing competitiveness of China as a seed industry powerhouse as well as improving people's eating and consumption habits. With the rapid development of life science, especially molecular biology and genomics, China’s aquaculture breeding has achieved fruitful scientific research results, but also encountered many bottlenecks and constraints. This paper synthetically summarizes the significance of carrying out aquaculture breeding research and analyzes the general situation of aquaculture breeding research in China. We also present the key problems that need to be tackled and solved, whose focus was mainly on four aspects. Firstly, the efficiency of germplasm resources utilization was still lower. Secondly, the traits owned by the cultivated varieties were not diverse enough. There are, in addition, seldom new techniques applied in the process of breeding and the imperfect commercial breeding system. On the basis of the research goals, the key scientific and technical tasks in the future are proposed that involve strengthening the excavation and efficient utilization of germplasm resources, attaching importance to fundamental research to strengthen source innovation, developing cutting-edge technologies to tackle key problems as well as focusing on market demand to cultivate excellent new varieties. Relevant countermeasures and suggestions are also made, such as building a germplasm resources conservation system, constructing a platform to support innovation, promoting the policy support for protection, and creating new research and development entities, etc. In summary, it is expected the information of this review could provide reference materials for China to lead the world in aquaculture breeding research and the transformation and upgrading of fisheries in the new era.

Abstract:With the development of high-density and intensive aquaculture, the water environmental factors stress such as dissolved oxygen, water temperature and ammonia nitrogen has become the restricting factor. The harmful environmental conditions severely decrease the fish growth rate, reduce fish resistance and increase the susceptibility to diseases, which ultimately causes significant economic losses in aquaculture industry. The cultivation of new resistance fish varieties is one of the important solutions and attracting more attention which is becoming the research hot. In this review, we summarize the response mechanisms to environment stress including the temperature, hypoxia, ammonia nitrogen, nitrous nitrogen and saline-alkali stress from the physiology to molecules. Furthermore, the breeding progress of new fish varieties with environmental tolerance and the molecular markers (gene, SNP, SSR and so on) related to environmental tolerance traits are presented. Finally, we point out that the first national aquaculture germplasm resources investigation should be applied to explore excellent germplasm resources. The research on the integrated response mechanism of fish under multiple environmental factors stress should be strengthened. Meanwhile, the efficient and precise breeding technology of the new varieties of environment-tolerance fish should be established based on the modern molecular breeding technologies such as molecular marker-assisted breeding, genome selection breeding, gene editing breeding, molecular module design breeding and so on. This review will provide the reference for the new fish varieties breeding with resistance.

Abstract:Primordial germ cells (PGCs) are the earliest germline stem cells established during embryonic development. The survival of species is dependent upon PGCs in sexually reproducing organisms. The specification of fish PGCs follows the pattern of “preformation” mode. In this mode, PGCs are specified by inheritance of maternal cytoplasm (germ plasm) during early embryogenesis. Specialized PGCs need to maintain their cell fates and migrate over long distances to reach the gonadal primordium. The biological processes of fish PGC specification, migration and fate maintenance are regulated by a variety of genes and signaling pathways. The study of fish PGC development is helpful for understanding the molecular mechanism of vertebrate cell specification, migration, and fate maintenance, and it is also important for developing new reproductive containment and germline stem cell transplantation techniques in farmed fish. Here, we review the research progress in fish PGC development and reproductive manipulation techniques, and look into rospect of their future development, hoping to provide theoretical and technical supports for the development of new techniques applicable to creating new germplasm of important farmed fish.

Abstract:China has more than 1 512 300 hm² of coastal mud. The mudflat mollusks as the dominant species in the intertidal zone possess many advantages, including fast growth, strong adaptability and environmental friendliness. Therefore, the development of mudflat mollusk aquaculture has great prospects, superior conditions and considerable potential. Zhejiang province has a long history of mudflat mollusk aquaculture and developed distinct characteristics and advantages in the aspects of cultivation technology and model, artificial spat collection and seed breeding, large-scale breeding and breeding of new varieties. However, it also faces severe challenges in the technology innovations and development of the mollusk seed industry. This paper reviewed the history and current status of mudflat mollusk aquaculture industry, seed production technology, germplasm innovation and variety improvement in Zhejiang province. Arrangement of the topics around the highly efficient and accurate evaluation of economic traits, breeding technology innovation, breeding of new varieties with high quality and stress resistance, key technologies and equipment research of efficient propagation, and seed industry system construction were discussed. The key tasks of new varieties breeding and seed industry development of Zhejiang mudflat mollusk in the future, especially in the 14th Five-Year Plan period are proposed.

Abstract:Mitogen-activated protein kinase kinases (MAPKKs or MKKs) are essential components of the highly evolutionarily conserved mitogen-activated protein kinase (MAPK) cascade, which play crucial roles in response to a variety of biotic and abiotic stresses and immune responses. However, very little information is available about the MKKs in S. maximus. In order to detect the roles of the MKKs in response to biotic and abiotic stresses in Scophthalmus maximus, we first identified the MKKs of S. maximus at the whole genome level through bioinformatics methods, and then analyzed the expression patterns of MKKs in different tissues and under different biotic and abiotic stresses using multiple stress-related RNA-seq datasets. As a result, a total of 9 MKKs of S. maximus (SmMKKs) were identified, and they were unevenly distributed on 7 chromosomes. Physicochemical characteristics, secondary structure and subcellular localization of the proteins they encode were predicted, respectively. Phylogenetic analysis revealed that SmMKKs were classified into 5 subfamilies. Conserved motifs, intron-exon structure and multiple sequence alignment not only provided evidences for the classification of MKK subfamilies, but also revealed high levels of conservation in evolution within and between subfamilies. Expression patterns of SmMKKs in distinct tissues and under diverse abiotic and biotic stresses were examined using multiple published RNA-seq datasets. As a result, SmMKKs showed obviously tissue-specific expression. In addition, SmMKK6a was extremely significant differentially expressed after infection with both Enteromyxum scophthalmi and Megalocytivirus. After heat stress, SmMKK6a also showed extremely significant differential expression. Furthermore, SmMKK4a, SmMKK4b, SmMKK6a and SmMKK7 were extremely significant differentially expressed after high- or low- salinity stresses. Among these candidate stress-responsive MKK genes, SmMKK6a showed extremely significant response to both abiotic and biotic stresses, demonstrating its potential functions in comprehensive anti-stress. This study may be the first to systematically identify and analyze the MKK gene family in turbot. The results not only demonstrate that SmMKKs play crucial roles in response to various biotic and abiotic stresses, but also provide important theoretical support for the development of molecular selective breeding for comprehensive stress-resistance in S. maximus.

Abstract:Silver carp (Hypophthalmichthys molitrix) is an important freshwater economic fish in China’s aquaculture industry. In 2020, six species of freshwater farmed fish in China had production greater than a million tons, of which the yield of silver carp was 3.8129 million tons, ranking second. Silver carp is widely distributed in natural waters, and plays a major role in regulating the ecological environment. In the process of H. molitrix culture, hypoxia has become an important factor restricting the increase of its yield. In previous studies, miR-17a-5p was identified and differentially expressed in H. molitrix under hypoxia stress based on the small RNA sequencing. The micro-ribonucleic acids (miRNAs), a class of endogenous and noncoding small RNA, play an important role in biological resistance to environmental stresses. In order to explore the role of miR-17a-5p in H. molitrix under hypoxia, sequence analysis and target gene prediction of miR-17a-5p was performed. The results showed that the miR17a-5p are highly conserved among species, and 381 target genes were identified, including HIF-1α. Dual-luciferase reporter assay results demonstrated that when 293T cells were co-transfected with miR17a-5p mimics and WT-pmirGLO-HIF-1α 3′UTR, the luciferase activity decreased, confirming HIF-1α to be a target gene of miR17a-5p. This conclusion is in agreement with the observation of the increasing trend of HIF-1α alongside the decreasing pattern of miR17a-5p under hypoxic stress in different tissue. KEGG pathway analysis revealed that the target genes were significantly enriched in Sulfur metabolism, mTOR signaling pathway and Terpenoid backbone biosynthesis. The expression of 11 target genes involved in the above three signaling pathways under hypoxia in liver, brain, heart and gill were detected by quantitative real-time PCR. The results showed that the overall trend of increase for the relative expressions of these genes, and upregulation was most pronounced in liver. In this study, we analyzed the bioinformatics of miR-17a-5p, predicted and further identified its target genes, and subjected H. molitrix to different degree of hypoxia stress, revealing that the downregulation of miR-17a-5p expression in H. molitrix under hypoxia stress attenuates its inhibitory effect on its target genes. Our finding provides a new idea for miR-17a-5p regulation of its target genes in H. molitrix under hypoxia stress, and provides a reference for further analysis of the role of miRNAs in the process of hypoxia tolerance of fish.

Abstract:Affected by natural factors such as temperature, season and weather, or human factors such as eutrophication and high stocking density, oxygen concentration in the water environment where fish live is unpredictable, and they are often faced with a low-oxygen environment. Studies have found that fish have evolved a complex physiological and biochemical system to adapt to the stress response caused by hypoxia in the water environment. However, severe and acute hypoxia can cause a large number of fish to suffocate and die in a short period of time. Because of its delicious taste, no intermuscular spines and high nutritional value, the L. longirostris has become one of the important freshwater aquaculture species in China. Currently, studies have been carried out at home and abroad on the growth characteristics, product processing and nutritional evaluation of this fish. There are few reports on its important ecological impact factor "hypoxia". In order to understand the regulatory mechanism of the brain tissue in response to hypoxic stress. In this study, enzyme activity determination, H.E staining, qRT-PCR, TUNEL detection and other methods were used. Changes in brain tissue of L. longirostris hypoxia response genes, physiological and biochemical indicators and appetite genes were analyzed and compared under hypoxic stress [(0.8±0.1) mg/L] 0, 2, 4 and 6 hour (labeled as H0, H2, H4 and H6) and recovery [(7.3±0.5) mg/L] 2,4 and 6 hour (labeled as R2, R4 and R6). The results showed that: Under hypoxic stress and recovery, the expression levels of oxygen-sensing protein-related genes (HIFs, PHDs and Vhl) in the brain tissue of L. longirostris showed a trend of first rising and then falling as a whole. Respiratory metabolic enzymes (HK, PK and LDH) activities were significantly increased at H0, SDH and MDH activities were significantly reduced at H6. After reoxygenation, the metabolic mode gradually changes from anaerobic respiration to aerobic respiration. Antioxidative enzymes (GSH-Px, CAT and SOD) and stress indicators (MDA and LPO) gradually increased after 2 h of hypoxia, and oxidative stress persists after the recovery of dissolved oxygen. Through the observation of brain tissue morphology, it was found that under hypoxia stress, neuronal cell swelling and vacuoles were damaged in the brain tissue of L. longirostris, which were not effectively improved after 6 hours of reoxygenation with dissolved oxygen. However, with the prolongation of hypoxia time, the degree of apoptosis of brain tissue cells increased, and the expression of apoptosis-related genes (Bax, Caspase-3 and p53) increased significantly, while the expression of Bcl-2 gene decreased, there are still significant differences in expression compared with the control group after the recovery of dissolved oxygen. In addition, it was found that the feeding rate of L. longirostris decreased by 54% and 98% at 0 h and 2 h of hypoxia stress, respectively. Hypoxic stress was detected to significantly inhibit the expression of appetite-promoting genes (NPY) and inducible food-suppressive genes (PYY, CCK and NUCB2). This experiment showes that hypoxic stress and reoxygenation have significant effects on oxygen sensor proteins, respiratory metabolism, oxidative stress, structural morphology, apoptosis and appetite in the brain tissues of L. longirostris. The results of this study provide a theoretical basis for elucidating the molecular regulation mechanism of L. longirostris brain tissues under hypoxia stress and reoxygenation, it has guiding significance for the intensive and healthy breeding of this fish and the selection and breeding of new hypoxia-tolerant species in the future.

Abstract:To evaluate the influence of SNP panels with different densities on the accuracy of genomic prediction of AHPND resistance of Litopenaeus vannamei, 26 full-sib families were infected with Vp_AHPND, and survival time of 686 individuals were recorded. A total of 242 individuals were genotyped by the liquid chip "Yellow Sea Chip No.1" (55.0 K SNP), and the genetic parameters of survival time after Vp_AHPND infection were estimated using the A, G and H relationship matrices. Eight low-density SNP panels (40.0 K, 30.0 K, 20.0 K, 10.0 K, 5.0 K, 1.0 K, 0.5 K, 0.1 K) were generated based on the 55.0 K SNP panel. GBLUP and ssGBLUP methods were used to predict the GEBV of survival time, and prediction accuracy was calculated by cross-validation method and compared with BLUP method. The estimated heritabilities of survival time after Vp_AHPND infection were high (0.68-0.79). At 55.0 K SNP density, the prediction accuracies obtained by BLUP, GBLUP and ssGBLUP were 0.424, 0.450 and 0.452, respectively, in the data set with 242 genotyped individuals (G242). The accuracy of GBLUP and ssGBLUP was 6.13% and 6.60% higher than BLUP, respectively. For the data set with 686 phenotyped individuals (P686), the prediction accuracies obtained by BLUP and ssGBLUP methods were 0.510 and 0.535, respectively. ssGBLUP showed 4.90% greater accuracy than BLUP. For 8 low-density SNP panels, genomic prediction accuracies were all low (1.1%-1.8%) in G242 and P686 data sets when the SNP density was greater than or equal to 10.0 K. With the decrease of SNP density since 10.0 K, the accuracy of genomic prediction also decreased in the two data sets, The density of 5.0 K decreased by 0.6%-2.6%, 1.0 K decreased by 5.8% -11.0%, 0.5 K decreased by 11.4%-17.2%, and 0.1 K decreased by 38.8%-41.6%. The correlation coefficients of genomic relationship coefficient and GEBV obtained using 10.0 K and 55.0 K SNP panels were all higher than 0.99, which indicates that the relationship between sibling individuals and their GEBVs can be accurately predicted by using the 10.0 K SNP panel. The results showed that the 10.0 K SNP panel could replace 55.0 K SNP panel to perform genetic evaluation for survival time after Vp_AHPND infection,which provided a reference for the design of low density SNP chips.

Abstract:In order to study the functions of class B type I scavenger receptor (SR-B1/SCARB1) in the metabolism, growth, immunity and other biological processes of Eriocheir sinensis, the cloning and spatiotemporal expression analysis of scarb1 gene in E. sinensis were analyzed, the changes of related tissue structure and carotenoid content after RNA interference were observed, the SNP markers of the gene were screened and their association with the growth related traits were evaluated. The results showed that the scarb1 gene in E. sinensis was composed of the two exons and one intron. The open reading frame (ORF) was 2 415 bp and 805 amino acids were encoded; phylogenetic tree based on the amino acid sequences showed that the highest similarity with 80.51% were found between E. sinensis and Portunus trituberculatus, indicating its high conservation among species. Its expression was detected in all tissues encoded, including hepatopancreas, intestines, blood cells, heart, gills and muscle tissues at different molting stages, but the relatively high expression existed in hepatopancreas, intestines and blood cells. After RNA interference in scarb1 gene for 15 days and 30 days, histological observation showed that the lumen of the hepatic tubules in hepatopancreas was blurred and partially vacuolized, and significant cavities appeared in the muscular layer and submucosa of the intestinal intima. The color of hepatopancreas changed from yellow to gray white, and the content of carotenoids decreased significantly. One SNP locus (C432T) was screened in the first exon of the gene, which was significantly correlated with the weight gain rate and carapace length growth rate after molting (P < 0.05). The results of this study provide useful guidance for genetic research of scarb1 gene in E. sinensis and its breeding.

Abstract:Sexual maturation in triploid Pacific oysters (Crassostrea gigas) varies widely among individuals. In addition to genetic factors, the influence of the environment on their gonadal development is also crucial. To investigate the epigenetic regulation mechanism of Htatip2 DNA methylation in gonadal development in the Pacific oyster, the homology, phylogeny, gene expression and DNA methylation profiles at different developmental stages of fertile and sterile gonads in the oyster were investigated. The results showed that the conserved structural domain of Htatip2 in the Pacific oyster had the highest homology with the Htatip2-like conserved structural domain in the Eastern oyster (C. virginica). qPCR analysis showed that Htatip2 was expressed in various tissues, with the highest expression in the female gonads. In addition, the expression of Htatip2 increased with gonadal maturation in fertile oysters and did not change significantly in sterile oysters. BS-PCR analysis showed that the DNA methylation level of Htatip2 in oysters decreased with gonadal maturation and was negatively correlated with the gene’s expression level. Finally, the results of dual luciferase reporter assay indicated that the methylated Htatip2 promoter fragment significantly inhibited luciferase activity compared to the unmethylated fragment. This study suggests that DNA methylation of Htatip2 may be involved in the gonadal maturation through inhibition of gene expression. This study provides an important reference for the involvement of epigenetic regulatory mechanisms in gonadal development.

Abstract:The technology of allogynogenesis has great application potential in the breeding of superior varieties. Carassius auratus var. pengsenensis is a kind of hermaphroditic triploid crucian carp with natural gynogenetic reproduction and it is one of the best freshwater breeding varieties in China. The development of gynogenesis of C. auratus var. pengsenensis induced with heterologous sperms can produce normal surviving progeny. The study on allogynogenetic biological effects in progeny can provide reference for the cultivation of excellent new varieties of C. auratus var. pengsenensis. In this study, the eggs of C. auratus var. pengsenensis were fertilized with sperms from Elopichthys bambusa and Culter alburnus for two successive generations, respectively. We succeeded in obtaining their second generation offsprings, P×G (C. auratus var. pengsenensis ♀ × E. bambusa ♂) and P×Q (C. auratus var. pengsenensis ♀ × C. alburnus ♂). The chromosomal karyotype, DNA content, morphological traits, and growth performance of offsprings were compared with P×P (C. auratus var. pengsenensis). The findings suggest that the karyotype formulas of P×G, P×Q and P×P was 3n=150=45m+66sm+27st+12t, 3n=150=54m+51sm+39st+6t and 3n=150=51m+48 sm+45st+6t, respectively. It is significantly different from the karyotype of E. bambusa (2n=48=10m+24sm+12st+2t) and of C. alburnus (2n=48=16m+26sm+6st). Furthermore, observed ratio of nuclear DNA content of P×G and P×Q to nuclear DNA content of P×P was within the 95% confidence interval (both 0.97), showing that P×G and P×Q produced by heterologous sperms were gynogenetic triploid fishes. The findings of principal component analysis based on morphological parameters reveal almost no overlap between the scatter plots of P×Q and P×G and P×P; there seem to be significant morphological differences between P×Q and P×G and P×P (P<0.05) that can be made preliminary discrimination by discriminant function (the accuracy rate reached 97.8%). These findings suggest that there is a significant allogynogenetic biological effects between P×Q and P×G progeny. As compared to P×P, P×G and P×Q demonstrated benefits in terms of mean body weight, mean body length, body weight growth rate and body length growth rate at each age, and P×G had significant benefits (P<0.05). In conclusion, sperms from both E. bambusa and C. alburnus can promote gynogenic development of C. auratus var. pengsenensis eggs, and different sperm sources have varied effects on the development of gynogenic nucleus and progeny, as expected from allogynogenetic biological effects. Through the research results, we can preliminarily judge the better sperm stimulation source, which lays the foundation for the subsequent breeding of C. auratus var. pengsenensis excellent new varieties.

Abstract:Phenotypic traits such as body weight and body length of fish are very important economic traits in aquaculture and genetic breeding. In order to avoid the uncertainty, error randomness and low efficiency of manual measurement, this paper develops an automated, non-invasive device based on Mask Region Convolutional Neural Network (Mask R-CNN) for fish image segmentation and phenotypic traits measurement. The device consists of two parts: an image acquisition device able to measure fish of different sizes (body length 1-40 cm) and control software. The control software based on Mask R-CNN can train and predict the target traits of images, and realize the measurement, storage and management of target data. The experimental results show that the average relative error in body length and body height of Larimichthys crocea measured by the device is less than 4%. The body weight was fitted with multiple regression models based on body length, body height and body surface area. The correlation coefficient between measured values and the real body weight was 0.99, the average relative error was 4%, and the average processing time for each image was 3 seconds, which was 8 times as fast as manual measurement. The data measurement device based on machine vision and image capture developed in this study can automatically, efficiently and accurately obtain morphological and weight data of L. crocea, which provides a more convenient and efficient phenotype evaluation tool for the evaluation of L. crocea germplasm resources, breeding of improved varieties and germplasm innovation.

Abstract:To evaluate the application potential of single nucleotide polymorphism(SNP) chip in the construction of the base population for breeding, three different populations (EE, PP and SS) of Litopenaeus vannamei were challenged by Vibrio parahaemolyticus (Vp_AHPND), and the genomic information of 146 samples was obtained using the independently developed 40K SNP liquid chip “Yellow Sea Chip No.1”. The genetic background was systematically investigated and acute hepatopancreatic necrosis disease (AHPND) resistance of populations was estimated. The Vp_AHPND challenge test indicated that there were differences in disease resistance between different populations. When the overall mortality was more than 50%, the survival rate of PP population was 12.9% and 11.6% higher than that of EE and SS populations, respectively. The phylogenetic tree was constructed by using 38148 SNP markers after quality control. The result showed that the individuals of the same family first clustered together, and then the multiple families of the same population clustered together. Principal component analysis and genetic structure analysis also implied that the 146 individuals could be accurately divided into 3 groups, which was consistent with the phylogenetic tree. The analysis of genetic diversity for three populations showed that the average value of observed heterozygosity (H_o) was 0.25-0.29. The average value of polymorphic information content (PIC) was 0.20-0.23. The differences on the above three parameters between three populations were very significant (P < 0.01). The coefficient of genetic differentiation (F_ST) among the three populations was 0.11-0.21, indicating that there was medium-high level of genetic differentiation. Genomic inbreeding analysis showed that the average inbreeding coefficients of EE, PP and SS populations were −0.05±0.06, 0.20±0.09 and 0.37±0.07, respectively. Some individuals of PP and EE populations showed high levels of inbreeding. Using single step genomic BLUP with metafounder(sssGBLUP-MF) model with genotype, phenotype and pedigree information, the estimated heritability of survival after Vp_AHPND infection was medium (0.24±0.07), indicating that the base population had a promising breeding potential. To summarize, the efficiency of constructing and evaluating the base population can be further enhanced by using the liquid chip "Yellow Sea Chip No.1".

Abstract:The abalone hybrids Haliotis gigantea ♀ ×H. discus hannai ♂ (GD) and H. discus hannai ♀ ×H. fulgens ♂ (DF) have been approved as national new aquacultural varieties by the Ministry of Agriculture based on their excellent high temperature resistance and growth rate. But the research on nutritional quality of these two hybrids was still limited. In this study, H. discus hannai (DD), H. fulgens (FF), H. hannai ♀ x H. fulgens ♂ (DF), H. gigantean (GG), and H. gigantean ♀ x H. hannai ♂ (GD) were chosen for a comparison of their nutritional components and textural profiles. The tested indexes include moisture, cholesterol, ash, protein, lipid, glycogen, collagen, mineral elements, delicious amino acids, taurine, fatty acid and texture profile. The results showed that DF and GD had certain advantages over their parents species in fullness, crude protein and taurine content. In delicious amino acids profile, DF and FF were rich in delicious amino acids, while GG had the highest proportion of bitter amino acids. In fatty acid profile, the order of the fatty acid nutritional values of the five varieties from high to low was DD, DF, GD, FF and GG. GG had the highest springiness and fracturability, while FF had the lowest fracturability. GD had no advantage over its parents in texture profile. According to an analysis based on entropy weight method, the texture score was highest in DD and lowest in DF. The flavor score was highest in FF and lowest in GG. The comprehensive scores from high to low were DD, FF, DF, GG and GD. Overall, DD had the best nutritional quality, FF and DF were inferior to GG and GD in texture, but better in flavor than GG and GD. Therefore, the nutritional quality analysis here will lay a technical foundation for the subsequent breeding focusing on meat quality traits and development of processed products.