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Asian seabass (Lates calcarifer) is an important foodfish species. It has been cultured in Singapore since the 1980s. A selective breeding program to improve growth, meat quality and disease resistance has been ongoing in Singapore since 2004. In 2012, outbreaks of the big belly disease (BBD) occurred in two batches of offspring generated by a mass-cross among F1 brooders in a hatchery. After the outbreaks, only 437 survived in 6000 F2 juveniles. Molecular parentage analysis with 10 microsatellites revealed that four parents (F1) produced high percentage of offspring that survived the BBD outbreaks. Eighty-two BBD survivor offspring (F2) were selected based on their growth performance at 90 days post hatch (dph), family origin and allelic diversity. They were used as brooders to generate F3. In a period of five years, these F2 brooders produced six batches of offspring, where no outbreak of BBD occurred. In the same period, outbreaks of BBD occurred in 4 out of 18 batches produced by F2 brooders selected for growth, with mortality rates ranging from 85.1% to 95.4%. In F3, the average body weight (57.1 ± 1.09 g, n = 3068) of the line for BBD survival was slightly lower than that (60.6 ± 2.29 g, n = 4280) of the line for growth at 90 dph. In both lines, the body weight of F3 was much higher than that (46.90 ± 0.19 g, n = 12117) of F2. The genetic diversity in the line for BBD survival (F3) was much lower than that in F3 line for growth due to small founder population. These data indicate that the selection of BBD survival during BBD outbreaks using molecular parentage analysis is effective to reduce BBD outbreaks. Avoiding further reduction of genetic diversity is essential in the line selected for increased survival against BBD. [ABSTRACT FROM AUTHOR]

China has been the top aquaculture producer in the world since 2002. Over 800 species and 240 improved varieties have been used in China's aquaculture, which is the most diverse collection of species on this planet. Species diversification, along with other aquaculture technologies, contributes significantly to the increase of China's aquaculture production, whereas the use of too many species in aquaculture has resulted in some issues related to the environment and sustainability. We provide an updated overview of the species currently used in Chinese aquaculture in this paper. We examine critically the main drivers of species diversification in China with examples. We also introduce Chinese approaches to improve and certify new species and varieties for commercial production. We believe that further species diversification is not a priority in China's aquaculture, while further improvement of aquaculture technologies for major and native species is essential for green, profitable, and sustainable (GPS) aquaculture. The implications of China's experiences with species diversification for global aquaculture species diversification are discussed. [ABSTRACT FROM AUTHOR]

Viral nervous necrosis (VNN) disease, caused by the nervous necrosis virus (NNV), is a devastating disease, leading to high mortality rate and huge economical loss in aquaculture. In the past 30 years, many studies on the virus, host responses to the virus infection and diagnostics have yielded a lot of knowledge on developing measures to prevent the VNN disease. Although genetic improvement of disease resistance through breeding is inheritable and has long-lasting positive effect on aquaculture, it is a very challenging task in conventional selective breeding for improving disease resistance. With the advances in mapping quantitative trait loci (QTL) and genome wide association studies (GWAS) for NNV resistance in aquaculture species, DNA markers and genes associated with NNV resistance have been identified, making the application of marker-assisted selection (MAS) and genomic selection (GS) for NNV resistance possible. A few genes for NNV resistance are identified and are being used for genome editing to rapidly improve NNV resistance. In this review, we present the current knowledge on the NNV, host responses to NNV infection, diagnostic methods and vaccines available for NNV disease. In addition, we summarize the current status of conventional and molecular breeding for NNV resistance and highlight future directions, including genome editing for improving NNV resistance in aquaculture. [ABSTRACT FROM AUTHOR]

Iridoviruses are DNA virus and have caused huge economic losses in the aquaculture industry. The aim of this study was to establish a colorimetric loop-mediated isothermal amplification (LAMP) protocol for the on-site detection of Singapore grouper iridovirus (SGIV). The SGIV-VP61 gene was chosen as the target gene to develop a colorimetric LAMP assay. The optimized condition of the colorimetric LAMP assay was incubation at 63?C for 1 h. Samples infected with SGIV could be detected with the color change from yellow into pink. The sensitivity of the developed assay is 5.66 copies/µL of the viral DNA template. This sensitivity was about 1000 times higher than that of conventional PCR while it was slightly lower than the one-step semi-nested PCR assay. A total of 60 DNA samples extracted from the fin tissue of the SGIV-infected Asian seabass were examined for SGIV by colorimetric LAMP, semi-nested PCR and conventional PCR. The results of the colorimetric LAMP assay showed 94.87 % agreement with the semi-nested PCR. In addition, the DNA extraction method using NaOH showed a better performance in the colorimetric LAMP assay. Taken together, the colorimetric LAMP established was a sensitive, rapid and specific method for the detection of SGIV. SGIV was not detected in samples randomly taken from a genetically improved line of the Asian seabass. However, some seabass obtained from the local markets were found to contain SGIV. Thus, the LAMP assay has the potential application in the diagnosis of iridovirus diseases in the aquaculture industry. [ABSTRACT FROM AUTHOR]