Genetic Characterization of Semi-Arid Sheep Populations in India using microsatellite markers

Panduranga Reddy Punuru ¹ Vinoo Regula ¹ Muralidhar METTA ¹ SUDHAKAR KROVVIDI ¹ Jaya Madhuri Bhumireddy ¹ Prasanna Baratam ¹ Ravikanth Reddy Poonooru ^2*

• ¹ Sri Venkateswara Veterinary University, Tirupati, India
• ² University of Missouri, Columbia, United States

A study was conducted to characterize different populations of semi-arid sheep from India using microsatellite loci and to elucidate the genetic divergence among them. Sheep populations from the semi-arid regions of India, including the officially recognized Nellore breed (with Palla, Brown, and Jodipi phenotypic strains) as well as local populations such as Macherla and Vizianagaram sheep, were analysed. Vizianagaram sheep population displayed the highest allele count (276) with a mean allele number of 12.545, while Nellore Palla had the lowest allele count (205) with a mean allele number of 9.318. Private alleles identified in the populations were 22, 33, 48, 57, and 41 for Macherla, Nellore Brown, Nellore Jodipi, Vizianagaram, and Nellore Palla sheep, respectively. The mean observed heterozygosity (Ho) values ranged from 0.587 to 0.732, while the expected heterozygosity (He) values ranged from 0.692 to 0.769 among the populations studied. The microsatellite markers demonstrated a high level of polymorphism, with the Polymorphic Information Content (PIC) value ranging from 0.61 to 0.85. The most notable genetic differentiation among the populations investigated was observed between Vizianagaram and Palla sheep, as evidenced by a high FST value of 0.180. Conversely, the lowest genetic differentiation was recorded between Macherla and Nellore Brown sheep, with an FST value of 0.011. Nei's unbiased genetic distance varied across populations, with the highest distance observed between Nellore Palla and Vizianagaram sheep (0.926) and the lowest between Macherla and Nellore Brown sheep (0.032), complementing the results of genetic differentiation using FST value. Bottleneck analysis conducted across all populations revealed an abundance of low-frequency alleles, suggesting the absence of recent bottlenecks. Effective population size is optimum in all populations except Nellore Palla and Brown sheep. Structure analysis and factorial correspondence analysis revealed that the five sheep populations under study were distributed into three distinct clusters, with Palla forming a separate cluster. Furthermore, the results of principal component analysis demonstrated that Palla sheep formed a separate sub-cluster within the cluster containing Brown and Macherla sheep. The findings provide valuable insights for conservation and sustainable utilization of the sheep populations for breeding programs.