Now showing items 1-6 of 6

    • Article

      Development and characterization of nine novel microsatellite markers for the milkfish Chanos chanos 

      BS Santos, MRR Romana-Eguia, ZU Basiao & M Ikeda - Conservation Genetics Resources, 2015 - Springer Verlag
      The milkfish, Chanos chanos, is an important aquaculture resource in Southeast Asia. Using NGS data, 72 microsatellite markers were developed. PCR product confirmation using agarose gel electrophoresis allowed the identification of 24 utilizable markers. Milkfish samples (n = 48) from a hatchery stock in Palawan, Philippines were analyzed for genetic variability at the aforementioned 24 loci. Consequently, nine of these microsatellite loci were noted to have high success rate in amplification, exhibited polymorphism with 19 maximum number of alleles and no null alleles. These are the first microsatellite markers to be developed and characterized for C. chanos that will efficiently enable genetic stock delineation and monitoring as well as marker-aided genetic improvement research.
    • Article

      Genetic assessment of milkfish (Chanos chanos Forsskal) stocks based on novel short tandem repeats for marker-aided broodstock management 

      MRR Romana-Eguia, BS Santos, M Ikeda, ZU Basiao & A Kijima - Aquaculture Research, 2018 - John Wiley and Sons
      Milkfish hatchery broodstock are either from on-grown wild-caught or hatchery-produced fry/juveniles. To determine if a marker-assisted management scheme can be formulated for improved milkfish hatchery production, milkfish stocks were genetically characterized using nine novel short tandem repeats or microsatellites. Eight wild-bred Philippine stocks (CLA, CUR, CAM, SIH, SBH-I1, HH, PAL and ZH-P0), four hatchery-bred stocks (SBH-I2, SBH-D, BoH and ZH-F1), two farm stocks of known mixed lineages (SPH and BDH) and one Indonesian hatchery-bred stock (WJH) were assessed. WJH was included since milkfish fingerlings from Indonesia reared in Philippine farms could be developed into future broodstock. Mean allelic richness (Ar) was highest in wild-bred stocks (9.5) and lowest in hatchery-bred spawners (9.1). Mean expected heterozygosities (He) were relatively similar in all stocks with wild-bred stocks slightly higher (0.67) than the others. An analysis of molecular variance indicated significant yet low genetic differentiation among stocks (FST = 0.013; p = .000) where variation (98.6%) was explained by intra-stock differences. In some of the domesticated stocks, reductions in mean allelic richness were observed in first generation hatchery broodstock (e.g. ZH-F1; Ar = 8.3), compared with their founder stock (e.g. ZH-P0; Ar = 9.4). The Indonesian stock was similar to local wild-bred stocks based on genetic variability indices; thus, it might be likely that the local stocks’ fitness traits could be comparable with the imported milkfish stock which has been perceived to be better. The quality of locally available farmed milkfish and prospects of formulating a broodstock management scheme for the production of good quality milkfish seedstock are herewith discussed.
    • Article

      Genetic changes during mass selection for growth in Nile tilapia, Oreochromis niloticus (L.), assessed by microsatellites 

      MRR Romana-Eguia, M Ikeda, ZU Basiao & N Taniguchi - Aquaculture Research, 2005 - Blackwell Publishing
      Two control (C1 or first control generation, and C4 or fourth control generation) and three selected (S1 or first selected generation, S2 or second selected generation, S4 or fourth selected generation) stocks of Chitralada Nile tilapia were analysed for microsatellite variation to determine the effect of size-specific mass selection on genetic variability. Genetic variation based on five microsatellite loci (UNH123, UNH147, UNH172, UNH222 and UNH216) showed a slightly higher allelic diversity in the selected stocks (7.4–10 alleles) than in the control stocks (6.8–8.8 alleles). Apparent reductions in the mean number of alleles and He values were noted in successive generations of both control and selected lines. Significant deviations from Hardy–Weinberg equilibrium because of an excess of homozygotes indicated inbreeding in all control and selected stocks. Although estimated inbreeding levels were not significantly different among selected and control lines based on Welch's t-tests, the increase in the degree of inbreeding within the selected line was higher (107.9%) than the control line (64.2%) after four generations. The implications of these results on the management and conservation of genetic diversity in improved breeds are discussed, while the importance of monitoring and minimizing inbreeding are likewise emphasized.
    • Article

      Genetic diversity in farmed Asian Nile and red hybrid tilapia stocks evaluated from microsatellite and mitochondrial DNA analysis 

      MRR Romana-Eguia, M Ikeda, ZU Basiao & N Taniguchi - Aquaculture, 2004 - Elsevier
      We analyzed microsatellite and mitochondrial DNA restriction fragment length polymorphism (mtDNA-RFLP) in two domesticated (NIFI and Israel) and four genetically improved (GIFT, GMT, FAC-selected and SEAFDEC-selected) Nile tilapia (Oreochromis niloticus) as well as five red hybrid tilapia (Oreochromis mossambicus × O. niloticus) stocks (BFS, FACred, NIFIred, HL, and PF) farmed in Asia. Microsatellite variation at five loci (UNH216, UNH172, UNH123, UNH147, UNH222) was more informative in characterizing stock differences than the mtDNA-RFLP markers that were based only on 14 restriction morphs. Contemporary microsatellite data showed that GIFT Nile tilapia had the highest mean expected heterozygosity (H>e=0.813), while GMT had the lowest (He=0.666). The unselected NIFI stock and SEAFDEC-selected were genetically similar, while GMT differed significantly from the other Nile tilapia stocks. Among the red tilapias, NIFIred had the highest He (0.715), while BFS had the lowest variability (He=0.567). The Taiwanese red tilapia HL and Thai NIFIred were genetically similar. Except for NIFI, most of the Nile and red tilapia stocks exhibited remarkably significant homozygote excess relative to Hardy–Weinberg Equilibrium (HWE), suggesting some degree of inbreeding. Asian Nile tilapias were more genetically diverse (pooled He=0.791; mtDNA nucleotide divergence value dA=0.009) than the red tilapias (pooled He=0.697; mean dA=0.004). This slight divergence between the Nile and red tilapias was also seen in the analysis of molecular variance (AMOVA; FCT=0.0018) and in genetic distance and nucleotide divergence dendrograms. However, the AMOVA revealed that the greater percentage of variation (99.33%) in the total genetic diversity of the surveyed stocks is principally due to differences at the individual level and not between nor within groups. The significance of these results is that they reflect and lead to new inferences regarding the selective breeding and culture methods used in managing these farmed stocks.
    • Article

      Growth comparison of Asian Nile and red tilapia strains in controlled and uncontrolled farm conditions 

      MRR Romana-Eguia, M Ikeda, ZU Basiao & N Taniguchi - Aquaculture International, 2010 - European Aquaculture Society
      Growth of several genetically improved Nile tilapia (GIFT or Genetically Improved Farmed Tilapia, FaST or Freshwater Aquaculture Center Selected Tilapia, SEAFDEC-selected) and domesticated red tilapia (BFS or Binangonan Freshwater Station, NIFI-red or National Inland Fisheries Institute red, HL or Hacienda Luisita) stocks were compared in controlled (tank) and uncontrolled farm conditions (lake-based cages) with unselected NIFI or Chitralada Nile tilapia as control. Specific growth rate differed significantly (P = 0.009) in tank-reared Nile tilapia stocks where GIFT grew best at 1.358%/day followed by FaST (1.307%/day), control stock NIFI (1.257%/day) and SEAFDEC-selected (1.202%/day). Genetic effect explained 84.4% of the variance in growth of Nile tilapia in tanks. Although Nile tilapia growth in cages followed the same trend where GIFT grew best at 1.570%/day, no significant stock differences (P = 0.479) were noted. Meanwhile, red tilapia reared in either tanks or cages showed no significant stock differences in terms of growth. However, survival of the red tilapia stocks in cages differed significantly with HL having the highest percentage survival at 93.3%. The different growth responses of the Nile tilapia stocks especially under controlled (tank) farm conditions were largely due to genetic factors (stock differences).Under uncontrolled farm conditions, environmental factors were generally observed to have also affected the survival and to some extent, the growth of Asian Nile and red tilapia stocks.
    • Conference paper

      Marker-aided genetic stock management: prospects in Philippine aquatic biodiversity conservation and aquaculture 

      MRR Romana-Eguia, M Ikeda & A Kijima - In MRR Romana-Eguia, FD Parado-Estepa, ND Salayo & MJH Lebata-Ramos (Eds.), Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia: Challenges in Responsible Production … International Workshop on Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia 2014 (RESA), 2015 - Aquaculture Department, Southeast Asian Fisheries Development Center
      With the advent of DNA marker-based technologies and applications, genetic stock assessment incorporating molecular marker information has become an important tool in managing resources both for aquaculture and stock enhancement. Local initiatives toward this end have been undertaken by several research and academic agencies particularly those with access to advanced molecular genetic laboratory facilities both in the Philippines and in collaborating foreign institutions. Funds coming from the Philippine Department of Science and Technology and/or international research grants have supported work on commercially valuable species such as tilapia, shrimp, mud crabs, abalone, milkfish and some high value marine fishes with a view of utilizing and in the process, demonstrating the significance of more scientific microlevel assessment of stocks. Information drawn from marker-aided genetic stock evaluation can contribute to a better understanding of the impact of how proper stock management can be more effectively achieved and how this method can gradually translate to improved yields both from culture and fisheries. This paper covers a review of the status of this technology as applied to ongoing fish conservation and aquaculture production efforts in the Philippines.