Training Manual Application of Genetics and Biotechnology in ...

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CXAPTER 2 GENETICS IN AQUACULTURE - A GLOBAL SCENARIO G. Gopikrishna Aquaculture is gaining importance as an aid to enhance the food requirement of people all over the world. It also offers cheap protein to millions of people. compared to plants and terrestrial animals where improved varieties are available, aquaculture mostly relies on unimproved stock. There are a few examples of pioneering selection programs for species such as Atlantic Salmon, Nile Tilapia and in India, we have the improved Rohu Carp. It would be desirable to have welldesigned breeding programmes in aquaculture with focus on selective breeding, in order to reap the benefits ~f conventional selection. Selection is the choice of individuals to be chosen as parents for the next generation. It does not create new genes but pools the genes responsible for desired characters. While running a selection program for a particular trait, the gene frequency of that particular trait in a population is increased. This results in a rapid response to selection which is translated as improvement. In terrestrial animals, the coefficient of variation for growth rate is 7-10% while it is 20-35% in fish and shellfish. The fecundity in aquatic animals is very high which allows a higher selection intensity in aquaculture. (Gjedrem, 1997) This explains the reason for the response to selection being high for growth rate in fishes and shellfishes. Hence, it would be worthwhile to go in for well-planned selection experiments or selective breeding in fishes/shellfishes. Another very important factor governing the selective breeding experiments is that the life cycle of the species of fishlshellfish which is to be improved genetically, should be closed. This means that the parents should breed, the progeny should be grown upto maturity and the progeny should be bred to obtain the next generation. Genetic studies are meaningless if the life cycle is not closed. There are several selection programmes in aquatic species worldwide. Rye (2005) indicated that 36 family based programmes are either in operation or under implementation woridwide. Half of these programmes target the salmonid species
and it is assumed that close to 100% of the current world aquaculture production of Atlantic Salmon is now based on stocks undergoing systematic genetic improvement. The corresponding number for other aquaculture species is quite low, but seems to be picking up. There are 11 programmes in Atlantic Salmon in countries such as Nonvay, Chile, Canada, Faeroe Islands, Iceland, Scotland and Ireland. Selection programmes in Rainbow Trout are in vogue in Norway, Denmark, Finland, Chile and USA. There is a programme each for Seabass and Sea bream in Greece. A programme for Red Tilapia is on at Ecuador. Selection programme in Nile Tilapia is in vogue in Philippines, Vietnam and Malaysia. There are five programmes in Marine Shrimp in India, USA, Columbia, China and Thailand. (Rye, 2005) In India, the pioneering work carried out at the Central Institute of Freshwater Aquaculture, Bhubaneswar, is the first selective breeding programme. The project started in 1992 under the Norwegian collaboration. The species taken was Rohu (Labeo rohita), as it enjoys consumer preference. The base population was derived from different rivers such as Ganga, Yamuna, Sutlej, Gomati and Brahmaputra. The first phase was from 1992-1997 and based on the encouraging results obtained during the first period, the second phase was launched from 1997-2003. The tagging was carried out using PIT (Passive Integrated Transponder) tags. The response to selection for growth has been substantial ( 43.5%). ( Iana et a1 2003) Growth appears to be the most important trait for selection in aquaculture species. Increased growth rate leads to shorter production cycles to market size thereby reduced economical and biological risks of aquaculture operations. Growth rate is also assumed to be genetically related to feed conversion efficiency. If we select for growth rate, we get improvement in feed efficiency also, due to the positive relationship. This is known as correlated response. A veq important factor here is that if we select for one trait which has got a negative influence on another desirable trait, then it would become very difficult to obtain genetic improvement in both the traits simultaneously. The more we select for one trait, deterioration starts for the other trait. In Norway, the pioneering work canied out in Atlantic Salmon since the early seventies, is worth mentioning. Salmon had been selected for growth rate and age of sexual maturation. The country is stiIl having the programme, of course with modifications like incorporation of carcass quality traits and disease resistance as
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Page 6 and 7: CHAPTER 1 Quantitative Genetics in
Page 8 and 9: If the sample adequately reflects t
Page 10 and 11: of genetic differences among the in
Page 14 and 15: additional selection criterion. The
Page 16 and 17: CHAPTER 3 MICROBIAL TECHNIQUES M.S.
Page 18 and 19: finally covering the cottop wool wi
Page 20 and 21: 1 .a . Plasmid isolation protocol:
Page 22 and 23: CHAPTER 5 GENE CLONING M.S.Shekhar
Page 24 and 25: CHAPTER 6 MITOCHONDFUAL DSA EXTRACT
Page 26 and 27: Nutrition and Captive Broodstock De
Page 28 and 29: Role of nutrition in captive broods
Page 30 and 31: CHAPTER 8 PROBIOTICS IN AQUACULTURE
Page 32 and 33: survival. It could have been due to
Page 34 and 35: LAB in endothermic animals Raised a
Page 36 and 37: I 1 Lacfococcus / mainly non-pathog
Page 38 and 39: BIOREMEDIATION OF COASTAL AQUACULTU
Page 40 and 41: greatly improves water quality and
Page 42 and 43: References Barkay, T. and Pritchard
Page 44 and 45: Scoop out the agar at various place
Page 46 and 47: By definition, an immunostimulant i
Page 48 and 49: Cytokines : Interferon, interleukin
Page 50 and 51: CHAPTER 12 Marine Bio-active Compou
Page 52 and 53: PseudoaItero~?torzas are generally
Page 54 and 55: extracted from the liver along with
Page 56 and 57: active polysaccharolytic bacteria w
Page 58 and 59: and exhibit an excellent content of
Page 60: Ebran., N JuIien, S, Orange, N Aupe

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