Abstract：The object of this study was to analyze the effects of melanocortin 3 receptor (MC3R) gene on chicken's (Gallus gallus) carcass traits. The single nucleotide polymorphisms (SNPs) of MC3R in Jinghai Yellow chicken were detected by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) combined with sequencing technology. Then the linkage disequilibrium (LD) and haplotype analysis were conducted. As a result, 6 SNPs were identified in the coding region of MC3R, which were C160A, G192T, C273T, G310A, G549A and G762A, respectively, and there's no strong LD between the SNPs. It was found that among the 6 SNPs, the mutation C160A resulted in an amino acid change from Leu to Met, and the mutation G310A resulted in an amino acid change from Gly to Ser, and the other 4 SNPs (including G192T, C273T, G549A and G762A) all resulted in none amino acid changes which were synonymous mutations. Five haplotypes and 11 diplotypes were formed in the group of 379 Jinghai Yellow chicken. The least square analysis showed that there were significant or highly significant differences (P＜0.05 or P＜0.01) in the carcass traits of Jinghai Yellow chicken (including live weight, carcass weight, breast muscle weight, leg weight, eviscerated weight, half eviscerated weight and abdominal fat weight) between the 2 different diplotypes. For the live weight of Jinghai Yellow chicken, the difference between diplotype H4H5 and H4H4 was not significant (P＞0.05), but both of them were significantly or highly significantly (P＜0.05 or P＜0.01) lower than other diplotypes. In the aspect of carcass weight, H3H3 and H3H4 diplotypes had the highest value which were significantly or highly significantly (P＜0.05 or P＜0.01) higher than other diplotypes, and H4H5 diplotype had the minimum carcass weight which were significantly or highly significantly (P＜0.05 or P＜0.01) lower than other diplotypes. The breast muscle weight of H3H3 and H3H4 diplotypes was significantly (P＜0.05) higher than H4H4, and highly significantly (P＜0.01) higher than H4H5. The leg muscle weight of H3H4, H2H5 and H1H4 diplotypes was highly significantly (P＜0.01) higher than H4H5, and significantly (P＜0.05) higher than H1H3 and H4H4 diplotypes. In terms of eviscerated weight and half eviscerated weight, H3H3 and H3H4 diplotypes were significantly (P＜0.05) higher than H1H1, H1H3, H2H4, H2H5 and H4H4 diplotypes, and highly significantly (P＜0.01) higher than H4H5 diplotype. For the abdominal fat weight, H3H3 and H3H4 diplotypes were significantly (P＜0.05) higher than H1H1, H1H4, H2H4, H2H5 and H4H4 diplotypes, and highly significantly (P＜0.01) higher than H4H5 diplotype. So H3H4 and H3H3 were the favorable diplotypes with good carcass traits, and H4H5 was the unfavorable diplotype with poor carcass traits. Therefore, MC3R might be the major gene or a gene linked with the major gene affecting chicken's carcass traits. This study may provide basic date for marker-assisted breeding of carcass traits in Jinghai Yellow chicken.
