Quantitative Trait Loci (QTL) Determination Of Important Traits In Common Carp (Cyprinus Carpio L.)

Natural resources of aquatic organisams are decreasing, due to overfishing, humanmanipulation and global climate change, through out the world. On the other hand, demandof aquatic protein is increasing. Thus, lack of resources and increasing human populationall over the world is a great challenage to ensure the food security. Scientists and researchesare engaged to find out the techniques those not only save the natural creature but increasethe production of organisams for welfare of human being. Aquacultre is one of thedeveloping technique that produce millions tons of aquaculture species to fulfil the marketdemand. Aquaculture industry is facing lot of problems, such as slow growth rate, low feedconsumption ration and deiseases etc, to increase productivity and profitability of aquaticorganisms. In this regards efforts had been carried out for last many decades to improve theimportant traits through conventional breeding methods to increase the production. It seemsan improvement by conventional method but could not improve the important desired traits.Main draw back of conventional breeding was that it is time consuming, laborious andenvironmental factor influence the athentisity during breeding process.In the modern developed technology of DNA sequencing have facilitate thebreeders to improve desired economic traits in little time period by markers-assistedselection (MAS) breeding. In this regard MAS requires the gene/DNA sequence or locusresponsible of controlling the desired trait. This is a modern genetic technology that hasbeen applied in many aquaculture species, significant progress have been observed inSalmonids and Tilapia.Common carp (Cyprinus carpio L.) is one of the important aquaculture species. Thefarming history of this economical fish is about4000years old. DNA sequencingtechnology has facilitated to develop the genetic resource of the Common carp. Hence, development of molecular markers/DNA sequencing facilitate for genetic linkage mapconstruction. The genetic linkage map is considered as fundamental tool to know thegene/locus controlling the important trait. The most genomic regions associated with theeconomical important traits are termed as Quatitative trait locus (QTL). QTL detection isconsidered as basic requirement for MAS breeding. In the present study QTLs associatedwith growth trait, including body wieht (BW), body length (BL) and condition factor (K),growth rate and swimming ability ralted traits, including body height (BH), snout length(SL), head length (HL) and tail length (TL), have been identified, by using differentfamilies of Common carp.BW and BL are economical important traits in aquaculture species influenced byQTL and environmental factors. A backcross (BC1) Common carp family, with86progeny, was utilized to construct genetic map for preliminary QTL, associate with BW,BL and K, mapping. The genetic map was constructed with366markers, including175SSRs and191SNPs from genes, coverage50linkage groups with an average markerdistance of18.5cM. A total of fourteen QTLs associated BW, BL and K were detected onten linkage groups (LGs). Among these QTLs detected, three (qBW8, qBL8and qK8)associated with BW, BL and K respectively, were mapped on LG8. qBW8and qK8wereidentified on similar interval neared locus HLJ2394explained14.9and20.9%of thephenotype variance, while qBL8was identified on separate nearby locus HLJ571with30.8%of phenotype variance. Two QTLs, qBW13and qK13, related with BW and K separately,were found on LG13at different locus with phenotype variance of25.3and20.9%. Othertwo QTLs, qBW19and qBL19, associated to BW and BL were mapped on same region nearSNP0626on LG19, and explained10.3and15.6%of phenotype variance. While other seven QTLs related with BW and BL were located on different LGs. Confidential intervalwas ranged from1.1to10cM.Growth rate is also one of the important economic traits in aquaculture speciesinfluenced by QTL too. Recently published complete genetic map of Common carp with307markers (including109SSR,31EST-SSR and167SNP markers) was used todetermine the number and position of QTLs effecting BW and growth rate.10th,11thand12thmonth old individuals of Common carp were measured, and seven QTLs were detectedin three linkage groups (LG1, LG6and LG20); three were significant QTLs (qBW2-6,qBW3-6and qBW3-20, P<0.001), and four were suggestive QTLs (qBW1-1, qBW1-6,qBW2-20and qBW3-1, P<0.01). The three significant QTLs related to BW2and BW3werein LG6and LG20and covered18and41cM, respectively. The explained variances ofqBW2-6, qBW3-6and qBW3-20were34.4,32.1and33.4%, respectively. The foursuggestive QTLs affecting BW1, BW2and BW3were in LG1, LG6and LG20and hadvariances that ranged from17.9to26.7%. The similarity of the QTL intervals for BW1,BW2and BW3in LG6suggested that these loci may affect growth continuously during theearly stage of growth and may be important for growth.We identified QTLs associated with swimming ability related traits (BH, HL, SLand TL) of Common carp on high density linkage map spanning3301cM, average distanceof5.6cM, in50linkage groups. Mapping family comprised on190offspring and627molecular markers were genotyped. A total of fifteen QTLs including four (qBH13, qBH30,qBH33, qBH48) for BH, four (qHL10, qHL18, qHL29, qHL48) for HL, three (qSL24,qSL27, qSL45) for SL and four (qTL15, qTL17, qTL18, qTL44) for TL were detected onthirteen linkage groups LG10, LG13, LG15, LG17, LG18, LG24, LG27, LG29, LG30,LG33, LG44, LG45and LG48. Each LG consisted on single QTL except LG18and LG48. LG18was found with two QTLs associated with HL and TL. While LG48was comprisedthe QTLs related with BH and HL. The phenotype variance was recorded from12.6to40.6%. Five QTLs qHL48, qSL45, qTL15, qTL18and qTL44explained phenotype variance of>20%with a significant level of0.047,0.049,0.037,0.025and0.023respectively. Theneighbored loci of these QTLs are considered as main region of chromosomes controllingthe traits.The markers, with lower QTL interval, have great influence on the important traits.Hence, these identified regions, on genetic map, will be main source of discovering genesassociated with traits of interest in Common carp. Hopefuly, thses findings will lead to abetter understand the factors that influence on these traits at a genetic level. Thus the resultswill promote the growth to higher production through marker-assisted breeding.