| Pork has always been the major meat consumed in China.With the continuous improvement of people’s living standards,people’s demand for high-quality pork is also growing.To meet the needs of consumers for high-quality pork,many research institutes and pig enterprises in China are jointly devoted themselves to the cultivation of pig breeds with high-quality pork.Under this background,our laboratory cooperates with Jiangxi Shanxia Investment Co.,Ltd.to cultivate a sire strain with high quality pork,namely Shanxia black pig,which was bred by an intercross between Berkshire boars and Licha black pig sows.In this study,651 offspring of Berkshire boars×Licha black pig sows（Shanxia black pig）,233 pigs from an intercross between Shanxia black pig and Lulai black pig,87 pigs from an intercross between Duroc and Shanxia black pig,53 Licha black pig and 68 Lulai black pig were involved in this study,and they were slaughtered after having been fattened to about 105 kg.The muscle samples of the Longissimus dorsi muscle between 9-12 ribs were collected from the left side of the carcass during slaughtering test.Meat color score,marbling score,p H value,a*,b*and L*values were measured at 45 min and 24 h postmortem,respectively.Shear force was recorded at 24 h,and intramuscular fat content was also measured by Food Scan.At the same time,muscle tissue samples were collected and taken back to the laboratory to extract genomic DNA.SAS was used to test the effect of sex on meat quality and calculate the simple correlation coefficient between meat quality traits.The"China Chip 1"50K SNP chip of pig was used for genotyping SNPs.Then,a genome-wide association analysis（GWAS）was carried out with Gene ABEL package of R to identify the genomic loci associated with meat quality traits.At the same time,PCR-RFLP was used to detect the association between the 6 bp deletion site of MYH3 gene and meat quality traits.In general,the meat quality of castrated boars is better than that of sows,especially at24 h.All of the meat traits recorded at 45 min were no significant differences between sexes except marbling score（P<0.0001）.All of the meat traits measured at 24 h had significant differences between sexes except a*value,meat score and shear force.There was a significant positive correlation between each meat quality trait at 45 min and it counterpart at 24 h（r≥0.1719,P<0.0001）,and most of them were correlated strongly.A total of 13 chromosomal regions（genomic loci）were detected to be associated with meat quality traits by GWAS,including 4 genomic significant loci.The most significant SNP was CNC10121195,located at 55.05 MB of chromosome 12.It was significantly associated with 9 traits including 7 genomic significant loci,among which the most significant trait was 24 hour a*value(P=3.78×10-20),and the additive effect of favorable allele A was 1.195±0.112.The 6-base deletion mutation of MYH3 gene was only significantly associated with marbling score at 45 min（P=0.0227）,marbling score at 24 h（P=0.0220）,b*value at 24 h（P=0.0202）and intramuscular fat content（P=0.0023）,but not with the other 5 traits significant association detected by GWAS.The association of the top SNP for each meat quality trait was stronger than that of the 6-base deletion mutation site of MYH3 gene,and the significant level of most traits was not at the same order of magnitude.Therefore,in this population,it can be excluded that the 6-base deletion mutation site of MYH3 gene was the causal mutation site of this genomic locus.A major site affecting meat quality was identified at 55.05 MB of chromosome 12 by GWAS,and the 6-base deletion mutation of MYH3 gene was excluded as the causal mutation of this genomic locus.Since this locus has big effects on several meat quality traits,it is worth further study.This study provides theoretical basis for molecular breeding of meat quality traits in Shanxia black pig. |
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