Genetic polymorphism of CSN1S2 in South African dairy goat populations

Abstract

Alpha-s 2 casein has a significant influence on protein content in goat milk, and the technological properties important for cheese processing. Specific alleles (A, B, C, E and F) of the alpha (α) s2 -casein gene (CSN1S2) result in higher protein, casein and fat content, and improved coagulation properties, which are useful for improved cheese making. The aim of this study was to investigate the polymorphism and genetic variation of CSN1S2 in South African dairy goats, using DNA sequencing technology. Sixty dairy goats (20 Saanes, 20 British Alpine, and 20 Toggenburg) and 20 meat-type goats were sequenced with four primers to distinguish among the seven known alleles for α s2 -casein. A total of four alleles (A, B, C and F) for CSN1S2 were observed among the dairy-and meat-type populations with ten genotypes across the populations. The A allele and the AA genotype were the most frequent across the populations, with the favourable AC genotype being the most frequent (0.300) in the Saanen population. Two unique genotypes were detected in the Toggenburg (BB and BF) and one in the meat-type goats (CF). The results indicate moderate genetic variation for α s2 -casein in the South African goat populations (42.3-63.6%). Low positive F ST values suggest limited inbreeding. This study confirmed the presence of favourable alleles in the South African goat populations, indicating room for genetic improvement using directional selection for favourable genotypes.

Genomic analysis of the origins of extant casein variation in goats

“…A previous study on Indian and Turkish goats (Chessa et al, 2007) reflected the same trend, with high frequencies of the A allele in the majority of the analyzed populations. With regard to the CSN1S2 and CSN2 genes, we found that the A and C alleles, respectively, were predominant, a finding consistent with what has been published in European, African, Turkish, and Indian goats (Sacchi et al, 2005;Caroli et al, 2006Caroli et al, , 2007Chessa et al, 2007;Gigli et al, 2008;Vacca et al, 2014;Tortorici et al, 2014;Kusza et al, 2016;Grobler et al, 2017). In the CSN3 gene, the A and B alleles were predominant in most populations (Table 1), as previously published in a broad array of caprine breeds (Yahyaoui et al, 2003;Prinzenberg et al, 2005;Caroli et al, 2007;Chessa et al, 2007;Kiplagat et al, 2010;Di Gerlando et al, 2015).…”

The Development and Genetic Improvement of South African Goats

“…To date, two studies have been performed to characterize casein in the SA goat breeds, one on κ-casein [46] and another on αS2-casein [47]. The first study investigated indigenous, Boer and Saanen goats using restriction fragment length polymorphism (RFLP) and DNA sequencing.…”