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On the gel, the DNA samples extracted using a commercial DNA extraction kit were appeared as smear (Figure 1a), whereas the DNA integrity was very high in salt-isopropanol precipitation method (Figure 1b). Investigation of genetic sex of GIFT strain of tilapia in Bangladesh using Y-linked Amh marker Keywords: all-male tilapia; Amh gene; aquaculture; GIFT; sex-linked marker EN all-male tilapia Amh gene aquaculture GIFT sex-linked marker 5737 5741 5 10/14/22 20221101 NES 221101 Nile tilapia has complex sex-determining mechanism and the system varies from population to population; even within a population variation has been observed. [Extracted from the article]

Stocking of all‐male fingerling produced by direct administration of male hormone 17‐α‐methyltestosterone is the most preferred method for present‐day aquaculture of the Nile tilapia Oreochromis niloticus. However, due to the growing concern of negative impact of steroid hormone in food fish, production of 'genetically male' tilapia, which depends on the concrete and thorough understanding of sex determination, has long been a scientific curiosity. The objective of the present study was to identify reliable sex‐linked markers and to evaluate the applicability of those markers in terms of monosex production approach. 'XY' neofemales were produced by using synthetic oestrogen and identified through selective breeding and progeny testing. Three females with progeny not deviating from 3:1 sex ratio (male:female) were designated as 'XY' neofemales and were used subsequently to produce putative YY progeny. Among the fifteen microsatellite markers tested, marker ARO172 was most informative in differentiating male and female genotypes. Twenty‐seven F2 fish from three families were identified as putative YY males based on marker genotyping, and four of them were crossed to produce F3 to validate marker association by progeny testing. The YY males produced 86%–100% male progeny indicating ARO172 a unique sex‐linked marker applicable in marker‐assisted selection. [ABSTRACT FROM AUTHOR]

Sex‐specific markers provide significant molecular basis for sex control breeding biotechnology to produce all‐male or all‐female fish in commercial breeding. Redtail catfish (Mystus wyckioides), one of the commercial bagrid catfishes distributed in Southeast Asian, which have a long sexual maturation period that can last 3–5 years and males have apparent growth advantage over females, but its sex determination system remains unknown. In this study, we first applied 2b‐RAD‐seq approach to identify three male‐specific 2b‐RAD‐tags and one male heterogametic SNP locus and validated by blast to the genome survey sequences and PCR amplification in both wild and breeding populations. To get longer sex‐specific region, we performed genome walking and obtained a 4,630 bp of Y‐specific sequence and 4,581 bp of X‐specific sequence from the 2b‐RAD‐tag ref189950 with 92.19% nucleotide identity between them. And 9,923 bp/3,935 bp of Y‐specific sequences and 8,491 bp/5,172 bp of X‐specific sequences were also identified with 77.49% and 57.07% nucleotide identity in ref208528 and ref210837, respectively. Subsequently, three different kinds of sex‐specific primers with different length products were designed based on the detected highly sex differentiated regions and could be used to distinguish males and females both in wild and artificially bred populations. What is more, the X‐specific fragment was discovered to produce the dosage effect association in females and in males. The data suggest that male heterogametic XX/XY sex determination system should exist in the redtail catfish. More significantly, the sex‐specific markers are of great value to protect wild resources and improve the efficiency of all‐male breeding practices for aquaculture in the redtail catfish. [ABSTRACT FROM AUTHOR]

The genetic structure of mrigal carp, Cirrhinus cirrhosus was analysed using six microsatellite DNA markers (MFW1, MFW2, MFW17, Bgon22, Barb54, and Bgon17) to detect genetic variations among fish samples from the three rivers, the Halda, the Padma, and the Jamuna in Bangladesh. All the populations showed polymorphism at all loci except Bgon17. Genetic richness of the Halda and Padma populations was indicated by the presence of rare alleles, two in Halda at MFW2 (160 bp) and MFW17 (201 bp), and one in Padma at Bgon22 (96 bp). The highest average number of allele (2.8) was observed in the Halda followed by the Padma (2.6) and the Jamuna (2.4). The observed heterozygosity (Ho) was highest (0.400) in the Padma followed by the Halda (0.383) and the Jamuna (0.377). The highest (0.0257) population differentiation (FST) value was observed between the Halda and Padma populations and the lowest (0.0143) between the Padma and Jamuna populations. The highest gene flow (Nm) was recorded between the Padma and Jamuna populations (17.1756) and the lowest between the Halda and Padma populations (9.4832). The highest (0.037) genetic distance (D) was observed between the Halda and Padma populations and the lowest (0.0195) between the Jamuna and Padma populations. The results indicated a low level of genetic variation regarding allelic richness and heterozygosity among wild stocks of C. cirrhosus and indicated it might be advisable to take necessary measures for the conservation and enhancement of C. cirrhosus genetic resources. [ABSTRACT FROM AUTHOR]