| Chinese native chicken breeds are famous for their tender and flavor. During the last years, the improvement has been made by traditional breeding methods. As the living conditions improved, the needs not only for meat production but also for meat quality are also increased. At present, more and more countries use IMP (inosine monophosphate) content as the criterion of meat flavor and freshness. But it is difficult to improve both the quantity and quality of meat by the traditional breeding methods. Therefore, the major genes and QTLs affecting meat quality are studied. Candidate gene method is one of the approaches used to study quantitative trait in animals. In this study, DNA samples from 448 chickens including five Chinese native chicken breeds: Taihe silky fowl, Beijing oil chicken, Chongren Ma chicken, Luyuan chicken, Xiayan chicken and one imported meat breed: Arbor Acres were analyzed. AMPD1 gene was studied by PCR-RF-SSCP. Meanwhile the alleles of AMPD1 gene were cloned and sequenced. The effect of different genotypes on IMP content was analyzed. The aim of this study was to determine the major gene affecting IMP content or the genetic markers tightly linked with it.Three alleles and six genotypes for AMPD1 locus in the six chicken breeds by PCR-RF-SSCP were found. The genotype frequency was significantly different (P < 0.01) among breeds. Allele A was not found in Taihe silky fow, alleles A, B and C were all found in other five chicken breeds. Allele B was the superior gene for Beijing oil chicken, Arbor Acres, Luyuan chicken, Xiayan chicken (allele frequencies were 0.6597, 0.5750, 0.7051, 0.7250 respectively). The test of Hardy-Weinberg equilibrium showed that Taihe silky fowl and Arbor Acres much diverged from the genetic equilibrium (P < 0.01). Study on polymorphic information content for AMPDl showed that Chongren Ma had highly polymorphic (0.5916) and the other five chicken breeds had moderately polymorphic.Cloning and sequencing of AMPD1 alleles A, B, C showed that allele B had only one base difference with allele A with C-->T(402), while allele C had eleven mutations with some base lost and others substituted: G-->T (361), the lost of A (373), the lost of T (404), G -->T (420), C-->T (434), G-->A (456), A-->G (469), G-->A (473), G-->A (486), G-->A (491), G-->A (493) (Because no sequence of AMPDl gene for chicken was enrolled in GeneBank, allele A was used as the criterion)Analysis of variance indicated that AMPD1 genotypes didn't significantly influence the IMP content (P>0.05). Least squares means of IMP content for AC and BB (3.7470, 3.1700) were higher than that for AA (2.4145)(P<0.05), and that for other genotypes not significant (P>0.05).It is necessary to have records of other five chicken breeds for further exploring genetic marker linked with major gene affecting IMP content by using more animals and combiningmore related candidate genes. It is certain that genetic marker will play more important role in marker assisted selection of animal breeding practice. |
