Abstract: Oujiang color common carp is the important species for freshwater culture due to their commercial value and ornamental value of fishery industry,which distribute over Lishui city,Longquan city,Qingtian country and Oujiang river basin in Zhejiang Province,China.It has several color patterns,such as completely red,red with scattered black spots,completely white,white with scattered black spots.Its culture can be traced back for 1200 years in local paddies,but no scientific studies have been undertaken until 2000.Since 2000,some domestic aquaculture scientists have carried out studies on the genetic diversity and exploitation and utility of Oujiang color common carp.Although several generations of "whole red" pattern of Oujiang color common carp have been selected and the offspring's body color isozygoty degree have been reached 90%,or so,little is know about the genetic structure and genetic differentiation of different generations.In this paper,ISSR technique was applied to investigate the genetic diversity among four generations of "whole red" patterns of C.carpio var.color,which were collected from the provincial farm of Oujiang color common carp,Longquan,Zhejiang Province.ISSR analysis was carried out according to previously established standard ISSR reaction system for Steed barbel with a slight modification.In brief,a 25μL of reaction system involved 2.5μL 10×PCR buffer containing Mg2+,20 ng DNA template,0.2 mM dNTPs,0.6 U Taq DNA polymerase,0.2m M primers and 0.5μL deionized formanide.ISSR-PCR reaction procedure was as follows:pre-denaturing at 94 ℃ for 5min followed by 5 cycles:denaturing at 94 ℃ for 30s,annealing at 55 ℃ for 45s,1 ℃ decreased for each cycle,elongation at 72 ℃ for 1.5min,sequently 35 cycles were included:94 ℃ for 30s,50 ℃ for 45s,72 ℃ for 1.5min with a elongation at 72 ℃ for 7min after cycle.PCR products were electrophoresed on a 1.5% agarose gel with ethidium bromide using DNA Marker-G as standard molecular weight control and photographed on UV imaging system BIO-RAD.Fifteen ISSR primers(screened out of 60 primers) were employed to scan the genomic DNA in 18 individuals of four populations,120,118,101 and 110 fragments ranging from 200 to 2500 bp were amplified from the above four stocks respectively.The experimental data were analyzed with Popgene version 1.31.As analyzed,the proportions of polymorphic loci in Oujiang color common carp ranged from 51.49% to 67.80%;the Shannon's information index(Ho) varied from 0.2176 to 0.2745 among stocks.With the increasing of selected generations,the selected populations showed a reduction in genetic diversity.H0 revealed that 70% variation occurred with populations.To test the genetic differentiation among four populations,genetic difference value(Gst),cluster analysis through UPGMA were also performed.The result revealed that the differentiation has taken place to some extent among "whole red" patterns of Oujiang color common carp,which the differentiations were large(Gst from 0.1588 to 0.2766) between the arbitrary two populations.The knowledge of their genetic structure and variation could be used to assist the selection of better ornamental carp,especially Oujiang color common carp in China.