بررسی ساختار ژنتیکی و روابط فیلوژنی اسب های کاسپین، عرب و تالشی

نژادهای بومی به دلیل دارای بودن ویژگی های منحصر به فرد، جزء ذخایر ژنتیکی کشور محسوب شده و شناخت بیشتر ساختار ژنتیکی آنها به حفظ و حراست آنها و تدوین برنامه های اصلاح نژادی کمک خواهد کرد. در این پژوهش تنوع ژنتیکی 136 راس اسب از سه نژاد ایرانی (کاسپین، عرب و تالشی) با استفاده از 12 نشانگر ریزماهواره توصیه شده توسط انجمن بین المللی ژنتیک حیوانی، مورد بررسی قرار گرفت. تمام نشانگرهای استفاده شده چند شکل بودند و نشانگرهای asb17 با 12 آلل و hms6 با 6 آلل به ترتیب بیشترین و کمترین تعداد آلل را تولید کردند. بیشترین و کمترین میزان هتروزیگوسیتی مورد انتظار به ترتیب در نشانگرهای vhl20 (78/0) و asb23 (62/0) محاسبه شد. میانگین شاخص شانون برای همه جایگاه ها برابر با 72/1 به دست آمد. در نمودار فیلوژنی رسم شده با استفاده از ضریب تشابه جاکارد و روش upgma (14)، اسب های کاسپین و تالشی در یک شاخه و اسب های عرب در شاخه جداگانه قرار گرفت. آنالیز واریانس مولکولی نشان داد که تنوع ژنتیکی زیادی در درون نژادهای بررسی شده وجود دارد و با توجه به جمعیت کم اسب های تالشی و کاسپین، پیشنهاد می شود برنامه های اصلاح نژادی جهت بهبود کارایی و جلوگیری از انقراض آنها تا رسیدن به سطح امن طراحی و اجرا گردد.

Investigation of the genetic structure and phylogenic relationships of Caspian, Arabic and Taleshi horses

Introduction[1]Due to having historical value and climatic diverse, Iran has unique horse breeds. Unfortunately, due to the lack of attention and control of the import of foreign breeds into this rich genetic source, huge damage has been created. Therefore, many horse breeds in the country got crossbred and their racial purity reduced. Knowing the genetic structure of native breeds will play an important role in their safeguarding and ensuring of their survival. Indigenous breeds, due to their unique characteristics, are considered as part of the genetic resources of the country, and their genetic structure will help them to protect and develop eugenic programs.;Materials and Methods This study was conducted on 136 horses including Taleshi (25 samples), Caspian (49 samples) and Arabic (62 samples) breeds from their breeding areas. Taleshi horse samples was captured from local stock in the Guilan province, Caspian samples was captured from horse riding clubs around Tehran and Guilan provinces, and Arabian samples was captured from horse riding clubs around the provinces of Tehran, Khuzestan and Alborz. They were unrelated and selected randomly. The race recognition of horses was based on books published by the Federation of Equestrian and their phenotypic characteristics. After determining of the concentration and uniformity of the concentration of extracted DNA, all individuals under study were conducted for 12 microsatellite markers recommended by the Animal Genetic Association (ISAG) to determine the genotype in order to estimate the parameters such as heterozygosity, inbreeding, Hardy and Weinberg equilibrium, and so on and find an appropriate strategy to maintain these valuable breeds. The number of observed alleles (na), and effective (ne), observed heterozygosity (Ho) and the Expectation case (He), Shannon index (I), inbreeding coefficient (ISF), genetic distance, genetic similarity, HardyWeinberg equilibrium, and phylogeny tree between races were calculated using POPGENE 1.31 software.;Results and Discussion All of the used markers were multishaped and the ASB17 markers with 12 alleles and HMS6 produced the highest and lowest number of alleles with 6 alleles, respectively. The highest and lowest expected heterozygosity were calculated in VHL20 (0.78) and ASB23 (0.62) markers, and the average Shannon index for all sites was 1.72. Hardy Weinberg balance analysis by Chi square test showed that except ASB2 and HMS3 markers in Taleshi breed, ASB17 and HTG4 markers in the Caspian breed and ASB17 markers in the Arabic breed, all markers had a significant deviation from Hardy and Weinberg equilibrium (P <0.05). The highest observed heterozygosity was related to AHT5 marker (0.81) and the lowest observed heterozygote was related to ASB17 and HTG4 markers (0.68). The Shannon index, like the observed heterozygosity, shows the amount of genetic diversity, and because the maximum value is equal to Ln (n), it is useful to express the genetic diversity of multiformed sites. The highest and lowest values of Shannon index were 1.96 and 1.46, respectively, for VHL20 and HTG4 markers. Given the fact that the VHL20 marker showed the highest and the HTG4 marker showed the least effective allele, so the calculated values for the Shannon index are justified. Phylogeny diagram showed that Caspian and Taleshi horses were placed in one branch and Arab horses in separate branch.;Conclusion Breeds with fewer populations are more at risk for genetic changes and extinction. Reducing of the genetic diversity of indigenous populations will result in the loss of many useful genes, especially those that are compatible with different environments and resistant to regional diseases. Undoubtedly, it is very important to pay attention to the genetic diversity of smallsized population of breeds such as Taleshi and Caspian. The results of this study showed that due to the low number of Caspian and Taleshi horses, genetic diversity is still at a high level, so it would be hoped that by adopting the principled measures, we would prevent their extinction in the long duration.;