Genetic variability of Girgentana goat breed using molecular markers

Assessing genetic diversity of local breeds through the information provided by neutral molecular markers, allows determination of their extinction risk and to design strategies for their management and conservation. The aim of this work was to quantify the levels of genetic variability in Girgentana goat breed using microsatellite markers and genetic polymorphisms at the casein genes. A total of 264 individuals were genotyped for 20 microsatellites, selected as suggested by ISAG and FAO. Moreover, the same individuals were characterized for the casein loci (CSN1S1, CSN2, CSN1S2, and CSN3) using PCR and sequencing protocols. Several genetic diversity indexes were estimated. A total of 130 alleles were observed considering the 20 loci analyzed. The mean observed and expected heterozygosities across loci were 0.586±0.204 and 0.604±0.203, respectively. The PIC was equal to 0.563±0.202. Heterozygosity deficit, as measured by Wright's Fis, was 0.035. The results showed moderate levels of variability for microsatellite markers in Girgentana goat, and may be explained considering the reduced effective population size. This breed is, indeed, reared in a restricted area of Sicily and nowadays about 650 animals are enrolled in the herd book. Based on the genetic structure of casein genes, the Girgentana breed showed high polymorphisms, similarity with most goat breeds from the Mediterranean area, and was characterized by the predominance of strong alleles, which play an essential role in the quantity, composition and technological properties of milk. Moreover, for CSN3 locus, two new genetic variants were identified, and named D' and N. In order to maintain genetic diversity, breeding strategies that increase effective population size minimizing genetic drift effect should be implemented.