MICROSATELLITE MARKER BASED ASSESSMENT OF GENETIC STRUCTURE OF MACHERLA BROWN SHEEP
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Date
2015-12
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SRI VENKATESWARA VETERINARY UNIVERSITY, TIRUPATI – 517502. (A.P.) INDIA
Abstract
ABSTRACT:
Macherla Brown sheep is the native sheep distributed along the banks of river
Krishna flowing through Guntur, Krishna, Prakasam and Nalgonda districts of Andhra
Pradesh and Telangana states. The home tract is mainly from the Nagarjuna sagar dam
areas of Guntur and Nalgonda. Macherla Brown is known for heat tolerance, disease
resistance and thrives well in harsh climatic conditions and scarce feeding conditions.
The assessment of genetic variation is important to characterize the populations for
breed recognition, conservation and also to determine the level of inbreeding in the
population.
The present study was carried out to assess the genetic structure of Macherla
Brown sheep at molecular level to understand the genetic variability and diversity of
population and to recognise this high performing local variety of sheep as a breed.
Twenty four ovine microsatellite markers recommended by ISAG/FAO for population
diversity studies in sheep were used in the present study. Phenol-chloroform method
was used for the isolation of DNA from the collected blood samples and the
microsatellite markers were amplified by PCR reaction. The amplicons were identified
using agarose gel electrophoresis. The genotypes were scored using regression equation
of the 100 bp DNA standard. The number, size and frequency of alleles were calculated
using POPGENE version 1.3.2 software.
A total of 275 alleles were observed for the twenty four marker loci under
investigation in the sampled Macherla Brown population. The number of alleles at each
locus varied from a minimum of eight (BM6506, HSC, OarCP34) to a maximum of
eighteen (MAF214) with a mean of 11.458 alleles. Allele size ranged from a minimum
of 69 bp (OarCP20) to a maximum of 313 bp (MAF214), while allele frequency varied
between 0.0102 (HSC, INRA63, MAF214, OarP49 and OarVH72) to 0.2551 (HSC).
The number of effective alleles across twenty four microsatellite loci studied ranged
from 5.8065 (HSC) to 14.1652 (OarFCB48). The mean number of effective alleles was
9.597 ± 2.454. The observed heterozygosity ranged from 0.0612 (BM8125) to 0.2653
(OarCP34) with a mean value of 0.110 ± 0.049 whereas, the expected heterozygosity
ranged from 0.8278 (HSC) to 0.9294 (OarFCB48) with a mean value of 0.889 ± 0.029.
All the twenty four microsatellite loci (100 percent) were found to be highly
polymorphic and the PIC values ranged from 0.8052 (HSC) to 0.9295 (OarFCB48). The
mean PIC value for all the twenty four loci was found to be 0.882 ± 0.036. The Chisquare
test revealed that all the twenty four loci were showing significant deviation
from Hardy-Weinberg Equilibrium. The inbreeding estimates obtained in this study
were all positive and ranged from 0.6915 (OarCP34) to 0.9341 (OarFCB48) with the
mean FIS value of 0.876 ± 0.057 indicating the high deficiency of heterozygotes.
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Keywords
Macherla Brown; sheep; GENETIC STRUCTURE; microsatellite markers