Objective To explore the resistant breeding situation of the receptor resistant alleles tva and tvb of A/K and B/D/E subgroups of avian leukosis virus within the 7th generation of the grandparental A, B and C lines of Zhanjiang Minglong Yellow feather broilers.

Method A total of 900 blood samples from the A, B, and C strains of the 7th generation of the ancestral line of Zhanjiang Minglong Yellow feather broilers were subjected to PCR amplification of the regions containing the resistant loci of the tva and tvb receptor genes. The sequencing results were genotyped, and the genotype frequencies and allele frequencies of each resistant loci of the tva and tvb receptor genes were statistically analyzed.

Result Genotyping of the resistant loci of the tva and tvb receptor genes in the 7th generation of the ancestral line of Zhanjiang Minglong Yellow feather broilers revealed that the tva^r3, tva^r4, tva^r5 and tvb^r3 resistant loci were present in all A, B and C lines. The highest frequency of the tva^r3 resistant allele in hens of the A strain reached 0.417, and the highest frequency of the homozygous resistant genotype tva^r5/r5 in roosters of the A strain reached 0.283; the highest frequency of the tva^r5 resistant allele in hens of the B strain reached 0.367, and the highest frequency of the homozygous resistant genotype tva^r4/r4 in roosters of the B strain reached 0.267; the highest frequency of the tva^r3 resistant allele in hens of the C strain reached 0.423, and the highest frequency of the homozygous resistant genotype tva^r3/r3 in roosters of the C strain reached 0.283. Among the A, B, and C strains, the frequency of the tvb^r3 resistant allele in hens of the A strain was the lowest at 0.908, while that in hens of the C strain was the highest at 0.958. Among them, the frequency of the homozygous resistant genotype tvb^r3/r3 in hens of the C strain was the highest at 0.917.

Conclusion By integrating the research findings on the genetic diversity of tva and tvb receptor genes, the 7th grandparent stocks (Lines A, B, and C) of Zhanjiang Minglong Yellow feather broilers have demonstrated significantly enhanced resistance to avian leukosis virus subgroups ALV-A/K and ALV-B/D/E. Furthermore, a comprehensive breeding system for avian leukosis resistance in this breed has been successfully established for the first time.