Abstract Oocyan(O) gene determines blue shell pigmentation of domesticated chicken. O locus is closely linked to ALEV1 on chromosome1 with a genetic distance of 2.3 cM. Blue eggshells contain protoporphyrin, biliverdin and zink biliverdin chelatate, which belong to the porphyrin metabolic pathway. A bioinformatic approach was first used to blast the genes for enzymes of porphyrin pathway and no gene was detected to specify O locus. Due to limited number of SSR markers around O locus, PCR-SSCP was then employed to search for candidate SNP markers. The sequence bearing a marker was found to be consisted of two transversions at Chr1:61754089T->A and Chr1:61754175A->T, respectively. Population screening showed that 81% of homozygous blue-shelled layers(OO) were classified as AA genotype at the SNP loci, while 89% of heterozygous blue-shelled layers(Oo) were AB genotype and 93% of tinted layers(oo) were BB genotype. The results indicated that there was a close association between O locus and SNP locus, which suggests that the marker locus can be used as a molecular marker in breeding for blue-shelled chickens.
