Bhassu, S.

Chong, L. K.

Siraj, Siti Shapor

Tan, Soon Guan

Usmani, S.

Yusoff, Khatijah

Chong, Lee Kim

Bhassu, Subha

Usmani, Sahar

Universiti Putra Malaysia Institutional Repository

FOR Category F10900: Agricultural SciencesPOPULATION GENETICS FOR MANAGEMENT ANDCONSERVATION OF AQUATIC RESOURCES ANDDNA FINGERPRINTING IN FISHES: RIVER CATFISHANDTILAPIAS.G. Tan, K.Yusoff, S.S. Siraj, L.K. Chong, S. Bhassuand S. UsmaniFaculty of Science and Environmental StudiesUniversiti Putra Malaysia, 43400 UPM, Serdang, Selangor,MalaysiaKeywords: DNA, genetic markers, fish, identification,characterisation.Introduction .The river catfish Mystus nemurus is widely distributed inmainland and archipelago Southeast Asia. Due to its goodflesh quality it is a popular fresh water fish food and is there-fore of interest to aquaculturalists, Not much genetic infor-mation is available on this fish thus far. Tilapia, Oreochromisniloticus is an important aquaculture fish in Malaysia al-though it is an introduced African fish. Our studies aimed todefine and characterize through the use of DNA level geneticmarkers species, stocks and populations of Mystus and Oreo-chromis before they are used in breeding programmes.Choices of stocks to be used in crosses should be made withthe knowledge of the genetic structure of the stocks and thegenetic distances between them (Ferguson, 1994). Geneticmarkers can also be used to help monitor crossing experi-ments. Tests were done to find possible associations betweenmolecular markers and traits of economic importance.Materials and MethodsRiver catfish samples from Perak, Kedah, Johore, Selangorin Peninsular Malaysia and Sarawak on Borneo island werecollected and brought back to our laboratory. Sample sizesranged from 25 to 50 fish from each location. They weretyped for DNA markers by using the Randomly AmplifiedPolymorphic DNA (RAPD) and the Amplified FragmentLength Polymorphism (AFLP) techniques. RAPD analyseswere done using agarose gel electrophoresis while AFLPtyping were done using polyacrylamide gel electrophoresis(Chong et al. 1998). In the case of tilapia, thirty fishes eachfrom five stocks namely Taiwan A, Taiwan B, Thailand,Philippines and Mossambicus being maintained by an inter-related breeding project at the Institute of Advanced Stu~iesresearch farm at the University of Malaya were typed usingthe DNA micosatellite technique adapted for use on agarosegel electrophoresis (Bhassu et al. 1998). Analyses of datawere done using suitable statistical packages such as NTSYSand MICROSAT (Goldstein et al. 1995).Results and DiscussionFor the river catfish among the five populations both RAPDand AFLP markers revealed high genetic variability withinthe Selangor and Sarawak populations with similarity indexvalues (SI) ranging 0.5556-0.8936 and 0.6667-0.9412 re-spectively in RAPD analysis and 0.5529-0.9321 and 0.4925-0.9595 respectively in AFLP analysis. The Sarawak popula-tion clustered by itself thus isolated from the Peninsularpopulations. Three subgroups, one each from Kedah, Perakand Sarawak populations were revealed by AFLP but notRAPD. In our studies nine RAPD primers revealed 42 andfour AFLP primers revealed 158 polymorphic markers. Un-fortunately, our family studies showed that for both RAPDand AFLP only dominant markers were observed in this spe-cies. While these markers are excellent for genetic charac-terisation of populations they are not efficient for testing forpossible associations between quantitative trait loci of eco-nomic importance such as growth rates and disease resistanceand molecular markers. Thus we have now initiated a studyusing a technique recently developed by Desmarais et al.(1998) called Direct Amplification of Length Polymorphisms(DALP) in order to obtain codominant DNA markers for thisspecies in the absence of DNA sequence data. We have thusfar identified five such codominant markers (Usmani et al.1998) and this study is being continued. For tilapia elevencodominant microsatellite loci were found to be polymorphicboth between and within the five stocks that were studied.Cluster analysis based on the genetic distances showed thatthe Philippines and Thailand strains were grouped togetherwhile Mossambicus formed another group and the two Tai-wan strains formed another cluster (Bhassu et al. 1998).Studies to find associations between the microsatellite lociand economic traits are in progress.ConclusionsThe results of our studies revealed high levels of interpopu-lation genetic variation in the river catfish Mystus nemurusespecially between the Peninsular and Sarawak populationsand that AFLP showed greater resolving power than RAPD.Similarly for the five tilapia stocks that we studied, sufficientheterogeneity exist among them to expect hybrid vigour toresult from suitable crosses. Natural populations of the Ma-laysian river catfish should be conserved to enable the richgenetic diversity of this species to be sustainably utilised toimprove our aquaculture industry.ReferencesBhassu, S., Yusoff, K., Panandam, I.M., Embong, W.K., Sivara-jayasingam, S., Oyyan, S. and Tan, S.G. 1998. Genetic variationat microsatellite loci in Tilapia fish, Oreochromis spp, In: Pro-ceedings of the 3'd National Congress on Genetics. p. 118-123.Chong, L.K., Tan, S.G., Yusoff, K. and Siraj, S.S. 1998. Amplifiedfragment length polymorphism analysis of Malaysian river cat-fish, Mystus nemurus. In: Proceedings of the 3,d National Con-gress on Genetics. p. 137-141.Desmarais, E., Lanneluc, I. and Lagnel, I. 1998. Direct amplificationof length polymorphisrns (DALP) or how to get and characterizenew genetic markers in many species. Nucleic Acid Research. 2:1458-1465.Ferguson, M. 1994. The role of molecular genetic markers in themanagement of cultured fishes. Reviews in Fish Biology andFisheries 4: 351-373.Goldstein, D.B., Linares, A.R., Cavalli-Sforza, L.L. and Feldman,M.W. 1995. An evaluation of genetic distances for use with mi-crosatellite loci. Genetics. 139: 463-471.Usmani, S., Tan, S.G. and Yusoff, K.M .. Development of direct am-plification of length polymorphisms in Mystus nemurus. In: Pro-ceedings of the 3"' National Congress on Genetics. p. 93-95.Supported by lRP A Grant 0 l-02-04-0074149

Population genetics for management and conservation of aquatic resources and DNA fingerprinting in fishes: river catfish and tilapia

Population genetics for management and conservation of aquatic resources and DNA fingerprinting in fishes river catfish and tilapia

http://psasir.upm.edu.my/20273/1/Population%20genetics%20for%20management%20and%20conservation%20of%20aquatic%20resources%20and%20dna%20fingerprinting%20in%20fishes%20river%20catfish%20andtilapia.pdf

Population genetics for management and conservation of aquatic resources and DNA fingerprinting in fishes river catfish and tilapia

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Universiti Putra Malaysia Institutional Repository

Universiti Putra Malaysia Institutional Repository