MOLECULAR ANALYSIS OF A NEW VARIANT OF THE EV21 INSERTION K-GENE COMPLEX IN THE SUPER SLOW FEATHERING NUNUKAN CHICKEN/

Alleles of the sex linked K-gene determine the rate of feathering in c hicks leading to rapid and slow feathering phenotypes and allowing sex identification of chicks. The slow feathering phenotype is associated with the integration of the endogenous viral gene ev21 coding for the complete, infectious, endogenous, avian leukosis virus EV21 and the r epetition of the integration site. Of our major interest is a new muta tion observed in the local population, Nunukan, from Kalimantan, Indon esia, characterized by a very slow rate of feathering (SSF = super slo w feathering). This new variant is expected to be favourable to overco me resistence problems to leukosis infections associated with the use of the K-Gen and to increase productive adaptability to tropical condi tions. A genomic library of a SSF female was prepared and a restrictio n map of a clone containing the ev21 Insertion was constructed for fur ther analyses. Furthermore a PCR test was designed to allow the rapid screening of different populations segregating for the alleles of the R-gene to search for rare genotypes. Another PCR test was developed in order to amplify the ev21 insertion and to detect the deletion of ev2 1 expected to exist associated with the SSF mutation. Sequencing of th e PCR product showed that a deletion of 4500 bp exist in the SSF mutan t covering the 5'-end of the ev21 insertion and about 650 bp of the 5' -flanking chicken genomic region. This deletion is a common feature of the SSF variant.