Genetic polymorphism at the milk protein genes (CSN1S1, CSN2, and CSN3) in the Czech Sumava and Walachian sheep breeds

The aim of this work was to determine allele and genotype frequencies at the casein loci, alphaS1-casein (CSN1S1), beta-casein (CSN2) and kappa-casein (CSN3) in two endangered Czech sheep breeds. The study was carried out on 265 sheep (133 Sumava, 132 Walachian) by means of PCR-RFLP and Light Cycler Analysis. These breeds are kept mainly for their good combined efficiency (milk, meat, wool). In particular, the genetic variant C at the CSN1S1 locus occurred with high frequency in both breeds Sumava (0.981) and Walachian (0.992). Variants A and D were either “absent” in Walachian (A=0.008, D=0), or present with a very low frequency in Sumava (A=0.008, D=0.011). Molecular analysis of the CSN2 locus showed that the genetic variant A were predominant, had higher frequency (Sumava, 0.778; Walachian, 0.829) than did variant G (Sumava, 0.222; Walachian, 0.171) in both sheep populations. The CSN3 locus was found to be monomorphic, with no polymorphism typed in either population. According to Hardy-Weinberg equilibrium, both breeds were in genetic equilibrium at the loci CSN1S1 and CSN2 (P<0.05). The information on the aggregate genotype variability in both breeds could be exploited in the future using specific breeding programs aimed at preserving biodiversity or select animals for the production of both unusual and typical milk products in the Czech Republic.