Characteristics of avian leukosis virus infection and polymorphism analysis of re-ceptor gene sequence in Qingyuan Ma chickens
In order to understand the characteristics of avian leukosis virus(ALV)infection and the polymorphisms of receptor genes Tva,Tvb and NHE1 sequences in different Qingyuan Ma chick-en breeding farms,the isolation and identification of exogenous ALV virus,receptor gene amplifi-cation and sequencing analysis were carried out in five Qingyuan Ma chicken breeding farms.The results of virus isolation and subtype identification showed that the positive rate of exogenous ALV virus isolation in farms A,B and C was less than 5%,among which there was ALV-J infection alone in farm A,mixed infection with ALV-J and ALV-K in farm B,ALV-K infection a-lone in farm C,and no exogenous ALV infection was detected in farm D and E.Polymorphism anal-ysis of recipient genes showed that there were different frequencies of Tvar3,Tvar4 and Tvbr3 re-sistance alleles in A-E farms,and the distribution frequency of Tvar3 was 0.2-0.6,the distribution frequency of Tvar4 was 0.3-0.7,and the distribution frequency of Tvbr3 was 0.1-0.7.In addition,there were Tvar5 resistance alleles in both B and D farms,with a distribution frequency of 0.2.A to-tal of 18 SNP mutations occurred in the NHE1 receptor gene sequence,and further analysis showed that positions 1 279,1 361,1 369,1 406,1 442,and 1 912 were non-synonymous mutations,which could cause changes in amino acids.The study suggested that there were differences in the exogenous ALV and its subtypes among the five Qingyuan Ma chicken breeders,and each farm should have a more targeted and unique purification strategy.The distribution of Tva and Tvb re-sistance alleles at different frequencies,along with the occurrence of 6 non-synonymous mutations in the NHE1 gene,indicate that Qingyuan Ma chicken have the potential of genetic resistance breeding.