Genetic assignment of Tunisian meat sheep breeds and the effect of the reduction of microsatellites number on their structure assessment

Abstract

Microsatellite markers succeeded to reveal different population genetic parameters. The present work aimed to investigate the genetic assignment and structure of the Tunisian meat sheep breeds. (Barbarin (BB), Western Thin Tail (WTT), and Black Thibar (BT)).The current study also opted for testing different methods of assignment implemented in several programs for genetic identification and traceability purposes of these breeds and for assessing whether these markers could be useful for an efficient genetic assignment of these ovine breeds. The genotypes of 90 animals (30 samples per breed) were typed for 22 microsatellite markers. All the loci displayed a high polymorphic content (between 0.561 and 0.884). The GENECLASS2 and the WHICHLOCI programs were used to choose the most powerful markers (17 microsatellites). The FLOCK program was more efficient with 22 markers. Genetic differentiation tests (FST = 0.0127) and assignment of individuals to populations revealed the highest level of misassignment in BB and WTT breeds, while the BT breed revealed the highest percentage of individuals assigned to itself. The reduction of the number of microsatellites (from 22 to 17) does not affect the assessment of the genetic structure of Tunisian sheep breeds. This result shed the light on the importance of the shift towards lambs with thin tails imposed by the butchers. It also revealed the unfitness of microsatellite markers in genetic identification analysis for studied sheep breeds.