Polymorphism of E. coli F18 receptor gene in different pig breeds.

The genetic variation of E. coli F18 receptor(ECF18R) loci in 867 pigs including Large Yorkshire, Landrace, Duroc, Ningxiang pig, Shaziling pig and Daweizi pig was detected by PCR-RFLP with Hin6 I. The results showed as follows: The three exotic breeds including Large Yorkshire, Landrace and Duroc were proved to be polymorphic at the Hin6 I-RFLP site. The average susceptibility genotype frequency of AG and GG in the exotic breeds was 0.94, G allelic frequency was 0.76. The C-->A mutation frequency at M307 site was very low in exotic breeds. The resistance genotype frequency of AA was 0.06. But the three native breeds including Ningxiang pig, Shaziling pig and Daweizi pig presented only GG genotype and no variation at the Hin6 I-RFLP site. The chi 2 value of ECF18R genotype distribution at the Hin6I-RFLP site in different pigs indicated that ECF18R genotype distribution of every exotic pig breed had significant or highly significant differences with three native pig breeds'. The ECF18R genotype distribution of three native pig breeds was the same completely. The others had no difference except that Landrace ECF18R genotype distribution had significant differences with Duroc's in the exotic breeds of pig.