Microsatellite markers to identify two species of Tilapiine fish, Oreochromis mossambicus (Peters) and O. niloticus (Linnaeus)
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Oreochromis mossambicus
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Nile tilapia
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Background and Objectives: Tilapia lake virus (TiLV) has been marked as an emerging infectious agent that causes mass die-offs in farmed mono-sex Nile tilapia (Tilapia niloticus) in Bangladesh, indicates rapid diagnostic assay.This study was aimed to develop molecular detection method to confirm the TiLV in Tilapia niloticus and construct a genetic baseline to control this disease. Materials and Methods:The research aims to the detection of TiLV followed by complementary techniques of PCR based approaches such as reverse-transcription polymerase chain reaction (RT-PCR) and RT-quantitative (q) PCR using SYBR Green I dye.The RNA quantification, followed by a PCR protocol entailing, complementary deoxyribonucleic acid (cDNA) synthesis and detection of TiLV by either conventional PCR or quantitative identification via qPCR using SYBR Green I dye.Results: This research reported a novel RNA virus allowing its clinical signs lethargy, skin erosion, exophthalmia, detached scales and 15-82% morbidity rate.The RT-PCR amplified a 491 bp fragment from segment 3 in both cases.The PCR amplification efficiency of 98.5% over a wide linear range of 2.98×10 1 to 2.98×10 10 TiLV copies, while the NTC (no template control) produced no fluorescence and therefore no amplification.The sequence of amplified PCR products received 100, 98 and 97% identity.The phylogenetic relationship of 17 TiLV sequences was chosen to compare with GeneBank resulting a common ancestor while closely related with Columbia, India, Malaysia and Thailand.The highest pair-wise alignment score was received 90.20 for MH338228.1 (Columbia), 85.57 for MF582636.1 (India), 85.30 for MH213048.1 (Malaysia) and 86.93 for MH213039.1 (Thailand) using the sequence of TiLV segments of one TiLV-positive strain.Conclusion: The mono-sex Nile tilapia was infected with common fish pathogens, such as Aeromonas and Streptococcus.This newly developed SYBR Green-based RT-qPCR assay can be as an essential tool for TiLV diagnostics and should help to control the dissemination of this virus worldwide.
Nile tilapia
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Ectotherm
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Monosex Nile tilapia (Oreochromis niloticus) is highly preferred in semi-intensive and intensive culture systems to prevent uncontrolled reproduction and to obtain fast growing male. Production of all male tilapia is being practiced by the hatcheries of Bangladesh mainly by administering androgen hormones (particularly 17-α-methyl-testosterone) with feed in a mixture of undifferentiated fry for about a month. The direct application of hormone to such food chain often arises question in respect to public health and safety. The alternative to this is the production of putative supermales, a rather safe but longer procedure to obtain all male progeny. However, sex determination system in tilapia is fairly complex. Recent developments have resulted in a linkage map and genetic markers that can be used to analyze the sex determination system. For genetic analysis of different genotypes of fish, microsatellite DNA marker ARO120 and ARO121 were used for studying the inheritance pattern for possible sex linkage using Polyacrylamide gel electrophoresis. In case of ARO120, it was observed that the Dam XX was heterozygous; 11 out of 22 female progeny and 10 out of 22 male progeny were found to be heterozygous. In case of ARO121, it was observed that the Dam XX was heterozygous; 16 out of 22 female progeny and 20 out of 22 male progeny were found to be heterozygous. Though the marker polymorphisms were observed in this study, these were excluded from the sexlinkage study due to limited extent of information as sex-linked markers in Nile tilapia BFRI strain. This study provides a baseline for further research using other suitable polymorphic markers for assisting marker-assisted selection.
Res. Agric., Livest. Fish.6(1): 143-151, April 2019
Nile tilapia
Genetic linkage
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Nile tilapia
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Nile tilapia
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