Abstract

Growth-related traits such as body weight,body length and condition factor are quantitative traits in-fluenced by a number of genes with relatively small effects,and environmental effects.These traits could be im-proved by phenotypic selection,but the genetic gain can be increased more rapidly with marker-assisted selection.Up to now,the genetic and molecular basis of growth-related traits is poorly understood in fish.A few QTL for growth-related traits have been detected with low density and fewer markers.Thus,more markers are needed to develop for mapping QTL.Recently,the newly developed TRAP(target region amplified polymorphism) marker is a reliable,stable and rapid PCR-based molecular marker technique.There are several advantages of TRAP over other DNA marker techniques.It has the favorable feature that combines high informativeness from the AFLP technique and easily performing from the RAPD method.TRAP markers use bioinformatics tools and EST data-base information to generate polymorphic markers around target gene sequences,while RAPD and AFLP are gen-erated by random anonymous sequences.TRAP maker has been effectively used in plant genetic research. In this study,the TRAP markers were used to analyze the genetic diversity and detect significant association between growth-related traits and polymorphism in an improved strain of common carp.The nucleotide sequences of three growth-related genes,including GH,GHR and IGF,were used to design fixed primer for pairing with four arbitrary primers.Finally,twenty-five combinations of primer were screened to be able to produce clear banding patterns and polymorphisms.The results showed that a total of 353 bands were scored with the 25 pairs of primer,of which 230 bands(65%) were polymorphism.The average of polymorphism information content(PIC),Nei's gene diversity and Shannon's Information index was 0.28,0.219 3 and 0.328 9,respectively.Genotypic differences of the 25 TRAP markers were analyzed using χ2 test between the large body weight group and small body weight group.Three loci(gh1Trap04-140,4rTrap04-308 and igf4Ga5-135) showing significantly differences in fre-quency in two groups(P0.05 or P0.01) were used in screening 132 individuals,and the associations between the loci and growth traits were examined by the procedures of generalized linear modeling(GLM) using SAS program.The result indicated that only the locus 4rTrap04–308 probably correlated with both body weight and body length significantly(P0.01).This study presents the first example of growth-related trait-markers detection in common carp using TRAP markers,and a possible functional gene locus related to growth was found in the population.It provided basis for localization of QTL concerning important traits and marker-assistant selection.

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