GENETIC POLYMORPHISM AND DIVERSITY OF IRAQI AWASSI SHEEP USING PCR-RAPD TECHNIQUE

The establishment of modern sheep production systems in Iraq, lead to presence of various forms of hybridization between the native and Middle East breeds which have been utilized for genetic improvement. This occur in consistence with the progressive destruction or deterioration of sheep habitat. Together, these factors have accelerated the loss of genetic diversity or even resulted in the extinction of some indigenous breeds. Therefore, it is important to develop efficient strategies for surveillance, evaluation, conservation and utilization of the available genetic resources for this species. Seven random ampliﬁcation polymorphism DNA (RAPD) marker used. The aim of this study was to assess genetic diversity for Awassi native breed in Iraq. The higher polymorphism information contents at the seven markers (Seventy- three bands obtained with 28.3% of polymorphism) indicate the retention of natural variation from source populations for the domestic breeds of different geographic regions in Iraq. Analysis of genetic differentiation revealed substantial divergence among these breeds as 16% diversity indicating that some evolutionary forces (e.g. selection and migration, uncontrolled selling across borders) had acted on these populations. Phylogenetic and phylogeographic analyses displayed a remarkable degree of consistency between geographic origins, breeding histories and the pattern of genetic differentiation.


INTRODUCTION
Sheep was perhaps the first ruminants domesticated around 10,000 B.C. Sheep were first domesticated probably in Iran and Baluchistan Awassi is the most widespread breed of sheep from a non-European origin. It is the most common breed in the east of Mediterranean. It is the main sheep breed in Iraq and Syria while the only native breed in Jordan (1). This breed adapts to a wide range of breeding systems ranging from the steppe to the highly intensive system.
Performance of this breed varies according to environmental condition and strain. Iraqi strain considered the heaviest and highest milk production among all Awassi populations. Efforts to improve milk production and body weight genetically lead to positive results. In Syria, a selection program succeeded to increase weight of sheep from 128 kg in 1974-1976 to 335 kg in 2005. In Turkey, the mean milk yield of ewes increased from 67 kg to 152 kg in a selection/outcrossing program that lasted for seven years. Although Awassi best known for its high milk production, this breed is often used as a triple purpose sheep in most of the countries of its origin in the Middle East (2) . Most of the domesticated sheep existed in Harappa and Mohenjo-Daro have traces from their origin of Mediterranean as well as Asian wild sheep. The need for conservation comes from the potential rate of decrease of genetic variation. The loss of genetic variation within and between breeds is detrimental. Once animal genetic diversity has been lost, it cannot replaced. Indigenous and locally developed sheep breeds are an important asset for many reasons, particularly because, over time, they have developed unique adaptive traits to respond to pressures of local environment (3) . Conservation of genetic resources requires the characterization of the available stock for preservation and management as well as evaluation of the phylogenetic origins of the genetic groups available (4) . The random amplification polymorphism DNA (RAPD) marker has been widely used, due to its easy utilization by simple PCR, followed by a denaturing gel electrophoresis for number of fragments and fragments size determination (5) . For all the above reasons the aim of this study was to assess genetic diversity for Awassi native breed in Iraq. DNA isolation and RAPD primers: Total DNA was extracted from blood sample using salting-out procedure according to (6) Promega blood kit was used to isolate genomic DNA from blood. Seven random primers (QIGENE China) used for DNA amplification. Each random primer was a 10-mer with GC content varying from 60% to 70%. Primers (OPAA11, OPU15, OPAA17, OPD18, OPA7, OPA9, and OPA10) selected for this study. The base sequence and length of the primers shown in Table 1.  Table 1: list of primers, their nucleotide sequence, range of band products, number of common and polymorphic bands, the percentage of polymorphism and diversity produced by different RAPD primers.

RAPD-PCR analysis:
RAPD  RAPD-PCR amplifications of each animal performed at l accuracy and the repeatability of the products. Amplification products separated by agarose gel (1%) electrophoresis and detected by ethidium bromide staining.

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PCR amplifications of each animal performed at least twice for confirmation of the accuracy and the repeatability of the products. Amplification products separated by agarose gel (1%) electrophoresis and detected by ethidium bromide staining.

RESULTS
The results of the DNA amplification showed that all primers ( This is also the case with the Iraqi local sheep breeds, whose numbers have decreased almost by half over the last decade. Extinction of any local breed or population may result in complete loss of some valuable alleles or genetic variations, which would affect the future genetic development. In spite of commercial value of Iraqi local sheep breeds, the information on the blood groups, blood protein polymorphism, traditional phenotypic characteristics, and the population structure of these breeds are virtually unknown. Although 10 bp primers or longer have been widely used in many RAPD-PCR studies in livestock (7,8) there are also reports using longer primers than 10 bp primers in livestock (9,10,11). The results showed variance in the number of bands for each primer ranged between five in OPD18to sixteen in OPAA17. Therefore, higher ds obtained yield more reliable information about the genotypes of