GENETIC DIVERGENCE OF VIZIANAGARAM AND MACHERLA BROWN SHEEP WITH NELLORE SHEEP: A STUDY
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Date
2018-01
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
ABSTRACT :
In India, most of the small and marginal farmers depend on sheep for their livelihood for which reason, they are considered as an important small ruminant. Several sheep breeds like Nellore and Deccani have been reared in different places of Andhra Pradesh for the past few decades and showing marginal gain to the shepherd community. Apart from these two characterized breeds, there are two other local genetic groups viz. Vizianagaram and Macherla Brown sheep reared by local shepherds. The Vizianagaram sheep are distributed in the North coastal region of Andhra Pradesh whereas Macherla Brown sheep are distributed in the villages adjacent to Krishna river in Guntur, Prakasam and Krishna districts. These two genetic groups of sheep are yet to be characterized and the genetic distances with other breeds is to be established. Phenotypic and production performances indicate that these two genetic groups are different from Nellore sheep. The objective of the present research is to study the genetic variation in the three genetic groups of Andhra Pradesh and their phylogenetic status using mitochondrial DNA control region. Blood samples were collected from six Macherla and Vizianagaram sheep respectively. Genomic DNA was isolated and 885 bp mitochondrial control region was amplified and sequenced. Metadata of Nellore and other Indian breeds were obtained from NCBI database and total of 341 sequences were aligned and trimmed to have a final length of 721 bp. The measures like polymorphism, divergence, gene flow and genetic differentiation were estimated using DnaSP software. A phylogenetic tree was constructed using Neighbour joining method by MEGA software. The tree topology was tested using 1000 bootstrap replications. The results of polymorphism and divergence analysis disclosed the existence of polymorphism in three genetic groups of Andhra Pradesh and these genetic groups were distinct. The findings of gene flow and genetic differentiation estimates concluded the presence of high differentiation and moderate sub-structuring of the three genetic groups in Andhra Pradesh similar to other sheep breeds in India. The phylogenetic analysis indicated that, all the haplotypes of the two genetic groups of sheep (Vizianagaram and Macherla) under present study are in lineage A along with majority of the other Indian sheep breeds. In Nellore sheep, out of 28 haplotypes, 26 were grouped in lineage A and 2 were grouped in lineage B. This separation could be due to the existing hypothesis that there may be two independent domestication events in India.
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