44 March 2012 7. Ethical issues in killing large numbers of fish, biosafety in the challenge facility, and proper disposal of dead fish and water used in the facility that can pose a threat to human health must be considered. Infection has an effect on the immune system and there are some correlations between immunological markers and disease resistance. The major concerns that should be considered are: 1. Immunological markers should be highly heritable. 2. The marker should be easy to measure in a standard laboratory within a short time. 3. Multiple factors are responsible in a cyclic manner for rendering protection to a disease. Therefore, it is difficult to develop a single marker for one pathogen. Hence, multiple immunological markers with high heritability and correlation with resistance should be considered, while developing indirect selection based on immunological markers. Emphasis should be placed on developing simple assay systems that allow measurement of a large number of samples simultaneously. Taking these criteria into consideration, molecular marker-based selection may be a good option for a successful selective breeding program for disease resistance. For developing the most-sensitive SNP and microsatellite marker-assisted selection program, prior knowledge of ESTs in the fish species is essential. The construction of genetic maps based on molecular marker information for a large number of loci would facilitate identification of quantitative trait loci of economic importance. Selectable molecular markers for resistance allows the maintenance of relatively few broodstock, thereby reducing time, cost and effort, and avoids sacrificing large numbers of potentially valuable fish. Molecular markers can also be used for selection in phylogenetically related species. Because molecular markers provide genetic information, heritability can be measured and associated with traits responsible for rendering disease resistance. In an e-mail conference hosted by FAO in 2003, representatives of 26 countries discussed molecular marker-assisted selection as a potential tool for genetic improvement of crops, forest trees, livestock and fish in developing countries (Guimaraes et al. 2007). Markerassisted selection is a complementary technology that can be used in conjunction with more established and conventional methods of genetic selection. Although the current impact of MAS on production of species and strains used by farmers is low, future possibilities and potential impacts are considerable. For developing countries, the main issues are the present high cost of the technology, limited infrastructure, absence of conventional selection and breeding programs, poor private sector involvement, and lack of research on species of importance. Intellectual property rights also play a vital role in the process. Therefore, collaboration between scientists in developing and developed countries, including the involvement of public-private partnerships, could pool and share resources, thereby reducing costs, and develop capacity to achieve breeding goals. Notes 1Central Institute of Freshwater Aquaculture, Bhubaneswar, Orissa, India References Angka, S.L. 1990. The pathology of the walking catfish, Clarias batrachus (L.) infected intraperitoneally with Aeromonas hydrophila. Asian Fisheries Science 3:343-351. Ardo, L., Z. Jeney, A. Adams and G. Jeney. 2010. Immune responses of resistant and sensitive common carp families following experimental challenge with Aeromonas hydrophila. Fish and Shellfish Immunology 29:111-116. Areechon, N. 1992. Situation on disease outbreaks in aquaculture of Thailand in 1991 and the forecast for 1992. Aquafarming 1:10-17. Areechon, N. and B. Karoon. 1995. Comparative study on resistance and immunological response of a hybrid catfish and the parent species to Aeromonas hydrophila. Pages 451-457 in M. Shariff, J.R. Arthur and R.P. Subasinghe, editors. Diseases in Asian Aquaculture II. Fish Health Section, Asian Fisheries Society. Manila, Philippines. Argue, B.J., S.M. Arce, J.M. Lotz and S.M. Moss. 2002. Selective breeding of Pacific white shrimp (Litopenaeus vannamei) for growth and resistance to Taura syndrome virus. Aquaculture 204:447-460. Bakos, J. and S. Gorda. 2001. Genetic resources of common carp at the Fish Culture Research Institute. FAO Fisheries Technical Paper No.417, Szarvas, Hungary:1-10. FAO, Rome. Dominik, S., J. M. Henshall, P. D. Kube, H. King, S. Lien, M. P. Kent and N. G. Elliott. 2010. Evaluation of an Atlantic salmon SNP chip as a genomic tool for the application in a Tasmanian Atlantic salmon (Salmo salar) breeding population. Aquaculture 308:56-61. Fjalestad, K.T., T. Gjedrem, W.H. Carr and J.N. Sweeney. 1997. Final Report: The Shrimp Breeding Program, Selective Breeding of Penaeus vannamei. The Oceanic Institute, Waimanalo, HI, USA. Gitterle, T., R. Salte, B. Gjerde, J. Cock, H. Johansen, M. Salazar, C. Lozano and M. Rye. 2005. Genetic (co)variation in resistance to white spot syndrome virus (WSSV) and harvest weight in Penaeus (Litopenaeus) vannamei. Aquaculture 246:139-149. Gjedrem, T. and H.M. Gjoen. 1995. Genetic variation in susceptibility of Atlantic salmon, Salmo salar L. to furunculosis, BKD and cold water vibriosis. Aquaculture Research 26:129-134. Guimaraes, E.P., J. Ruane, B.D. Scherf, A. Sonnino and J.D. Dargie. 2007. Marker-assisted selection – Current status and future prospective in crops, livestock, forestry and fish. Food and Agriculture Organization of the United Nations, Rome. Henryon, M., P. Berg, N.J. Olesen, T.E. Kjaer, W.J. Slierendrecht, A. Jokumsen and I. Lund. 2005. Selective breeding provides an approach to increase resistance of rainbow trout (Oncorhynchus mykiss) to the diseases, enteric redmouth disease, rainbow trout fry syndrome, and viral haemorrhagic septicaemia. Aquaculture 250:621-636. Henryon, M., A. Jokumsen, P. Berg, I. Lund, N.J. Olesen and W.J. Slierendrecht. 2002. Genetic variation for growth rate, feed conversion efficiency, and disease resistance exists (Continued from page 42)
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