Genetic diversity and structure of 2 indigenous sheep breeds (Kotel and Teteven) in Bulgaria using microsatellite markers

Abstract

This study analyzed the genetic diversity and structure of two Bulgarian indigenous sheep (Ovis aries) breeds -Kotel and Teteven, each presented by 4 flocks, using 15 microsatellite markers. A total of 195 alleles were identified. Among the markers used, the most informative were INRA5 and OarFCB20 with PIC values of 0.87. Both breeds showed a high level of genetic diversity with average values of He and Ho, respectively 0.74 and 0.76. The observed high level of genetic diversity is combined with the absence of heterozygous deficiency reported as Fis values of 0.04 and 0.07, respectively for Kotel and Teteven breeds. Low level of genetic differentiation between the two breeds was observed, as evidenced by the low value of Fst of 0.09, and analysis of variance (ANOVA) data showing that only 9% of the total variation is due to variation between breeds, whereas 91% is due to variation within breeds. Furthermore, we revealed a breeding practice that comprises an exchange of animals between the breeds which reflects in the clustering obtained by STRUCTURE analysis. According to it, Kotel breed is a more homogenous population and forms cluster 1, whereas Teteven breed is more heterogenous and consists of two subpopulations that form two distinct clusters. The results obtained in the present study confirm the high potential of microsatellite markers in studies related to both breed affiliation and purity and can serve as a basis for the implementation of future management and conservation programs of these indigenous breeds.

Microsatellite Genotyping of Two Bulgarian Sheep Breeds

“…The low values of F IS found in the RT breed (F IS = 0.01) and MRS sheep (F IS = 0.02) indicate a very low deficit of heterozygous individuals (Table 3). These results are in agreement with those published by Mihailova [46] considering two autochthonous Bulgarian breeds; however, they are in contrast with the findings of Hristova et al [16] for seven indigenous sheep breeds in Bulgaria and those of Kusza et al [47], who used 16 STR markers to study the genetic relationship among five Bulgarian sheep breeds.…”

“…Two loci of the RT sheep (ETH152 and INRA063, p < 0.001) and two microsatellite markers of the MRS (ETH152, p < 0.05; MAF214, p < 0.01) showed a significant deviation from HWE. Similar results have been obtained for other local Bulgarian breeds, such as the Breznishka, the Blackhead Plevenska, the Kotel, and the Teteven sheep breeds [16,46]. The low values of F IS found in the RT breed (F IS = 0.01) and MRS sheep (F IS = 0.02) indicate a very low deficit of heterozygous individuals (Table 3).…”

“…The average Ne in our study was 4.96. This value was higher when compared with the Teteven and Kotlen sheep breeds' Ne (4.33) [46]. In contrast, the average Ne value in this study was lower than the estimated values for some other breeds, such as Breznishka, the Sofiiska, the Copper-Red Shumenska, the Karakachanska, the Local Karnobatska, the Blackhead Plevenska, and the Starozagorska sheep breeds (Ne 10.07) [16].…”

“…Furthermore, the admixture could be due to the high flow of genes between the two studied breeds, most likely due to the involvement of indigenous animals from the MRS in the creation of the RT breed. In contrast to the studied breeds, other Bulgarian sheep breeds have shown much higher values of F ST [16,[44][45][46]. The F IS value for the overall population (0.033) is lower than the values found in other indigenous Bulgarian sheep breeds [16,47], Tunisian sheep breeds [48], and Moroccan sheep breeds [49], but higher than those observed in Turkish sheep breeds [50] and the Cuban Pelibuey sheep breed [51].…”

“…The data from the present study have shown that Ho was higher than He in 6 out of 12 microsatellite loci, thus indicating an absence of heterozygote deficit. On the whole, the observed heterozygosity was higher than that in other Bulgarian sheep populations [46,47], which could be explained by the different choice of a microsatellite panel used for genotyping, as well as the different breeds studied (Table S1 in Supplementary Materials). The Ho in the Rhodopean Tsigai (0.76) was compared with other Tsigai populations in neighboring countries due to the fact that the Russian Tsigai has provided the basis for the creation of the Tsigai type sheep breeds.…”