Genetic diversity in katchaikatty sheep based on microsatellites polymorphism

Sheep is one of the important species of livestock in India contributing to meat production. India has 44 distinct breeds of sheep, out of which 10 are found in Tamil Nadu. The present study describes the characterization of recently registered breed-Katchaikatty sheep, genetic variability and genetic structure of the population by microsatellite marker analysis.

The genomic DNA from 50 unrelated Katchaikatty sheep was amplified with 25 FAO recommended fluorescent tagged ovine-specific microsatellite markers and genotyped on an automated Genetic Analyzer. Microsatellite fragment sizing was performed by Gene Mapper software. In each locus, observed (n_o) and effective number of microsatellite alleles (n_e), allele frequencies, observed (H₀) and expected (H_e) heterozygosity, heterozygosity deficit estimate (F_IS) and Chi-square (X²) test for Hardy-Weinberg equilibrium (HWE) were assessed by POPGENE software and polymorphism information content (PIC) was calculated. Mode-shift analyses were performed for testing the genetic bottleneck by bottleneck software.

The study revealed a total of 144 alleles across all the loci. The number of alleles at each locus varied from one to 10 with a mean of 5.76 alleles. The PIC values in the microsatellite loci ranged from 0.34 (OarAE129) to 0.83 (OarFCB48) with an average of 0.59, which showed a high genetic polymorphism. Six out of 25 microsatellite loci studied were in Hardy-Weinberg equilibrium and 19 out of 25 loci showed positive F_IS values. The overall mean observed and expected heterozygosity were 0.50 and 0.65 respectively and the estimates elucidated a substantial genetic variability in Katchaikatty sheep population. Mode shift analysis revealed a normal L-shaped curve, describing that the Katchaikatty population had not experienced any genetic bottleneck and remained in mutation-drift equilibrium.