تخمین نرخ هم‌خونی با استفاده از رشته‌‌های هموزیگوت ژنومی و بررسی روند تکاملی اندازه مؤثر جمعیت در برخی از نژادهای اسب آسیایی

نوع مقاله : مقاله پژوهشی

نویسندگان

استادیار، گروه علوم دامی، دانشکده کشاورزی و منابع طبیعی، دانشگاه اراک، اراک، ایران

چکیده

هدف از این تحقیق محاسبه هم­خونی با استفاده از رشته­­های هموزیگوت ژنومی و بررسی روند تکاملی اندازه مؤثر جمعیت (Ne) در برخی از نژادهای اسب آسیایی بود. به این منظور از اطلاعات ژنومی مجموع 99 نمونه حیوان شامل 19، 24، 18، 19 و 19 نمونه به­ترتیب از نژادهای آخال­تکه، عرب، کاسپین، مغولی و تروبرد استفاده شد که با به­کارگیری آرایه­های Illumina SNP50K Beadchip تعیین ژنوتیپ شده­اند. این تحقیق با همکاری کنسرسیوم تنوع ژنتیکی اسب (EGDC) انجام شد. ضریب هم­خونی با استفاده از روش FROH بر پایه رشته­­های هموزیگوت ژنومی (ROH) و اندازه مؤثر با به­کارگیری اطلاعات عدم تعادل پیوستگی در طی 5 تا 1000 نسل قبل محاسبه شد. نتایج آنالیز مؤلفه­های اصلی (PCA) نشان داد که تمام نژادها با استفاده از دو مؤلفه اول از همدیگر مجزا می­شوند. میانگین هتروزیگوسیتی مورد انتظار و مشاهده­شده در نژادهای مختلف به­ترتیب در دامنه 294/0-278/0 و 308/0-278/0 بود. محاسبه ضریب همخونی بر پایه اطلاعات ژنومی نشان داد که مقادیر محاسبه شده بین 003/0 (نژاد مغولی) و 166/0 (نژاد تروبرد آمریکایی) در نوسان می­باشد. نتایج حاصل از محاسبه اندازه مؤثر در نژادهای مختلف، نشان­دهنده روند کاهش تدریجی Ne در طی 1000 سال گذشته تاکنون با یک شیب کاهشی زیاد در حدود 100 نسل قبل برای تمام نژادها بود. بیشترین Ne در نسل­های حاضر (5 نسل قبل) در نژاد عرب (53 رأس) و کمترین در نژادهای کاسپین و تروبرد (33-34 رأس) مشاهده شد. در مجموع، نتایج این تحقیق نشان داد که در بین نژادهای آسیایی، نژاد اسب کاسپین با وجود تنوع ژنتیکی مناسب و ضریب همخونی پایین، اندازه مؤثر آن نسبت به سایر نژادهای مورد مطالعه در این تحقیق کمتر می­باشد که طراحی برنامه­های مناسب برای حفاظت از حیوانات خالص باقیمانده این نژاد بومی کشور ضروری است.

کلیدواژه‌ها


عنوان مقاله [English]

Estimation of inbreeding values using genomic run of homozygosity and study of evolutionary trend for effective population size in some Asian horse breeds

نویسندگان [English]

  • Amir Hossein Khalt-Abadi Farahani
  • Mohammad Hossein Moradi
Assistant Professor, Department of Animal Science, Faculty of Agriculture and Natural Resources, Arak University, Arak, 38156-8-8349, Iran
چکیده [English]

The objective of the present study was to estimate the inbreeding values using run of homozygosity and study the evolutionary trend of the effective population size (Ne) in some Asian horse breeds. A total of 99 animal samples consisting 19, 24, 18, 19 and 19 samples from AkhalTake, Arrabian, Caspian, Mongolian and Thoroughbred breeds, genotyped by Illumina SNP50K Beadchip assay were used in this study, respectively. This study has been performed in collaboration with the Equine Genetic Diversity Consortium (EGDC) project. The inbreeding values based on the run of homozygosity using FROH and next, Ne using linkage disequilibrium across 5 up to 1000 generations ago were estimated. The result of principal component analysis (PCA) indicated that all breeds will be separated from each other in the first two principal components. Average expected and observed heterozygosity for different breeds ranged 0.278-0.294 and 0.278-0.308 respectively. Estimation of inbreeding based on genomic information showed that the values are ranged between 0.003 in Mongolian up to 0.166 in Thoroughbreds. The Ne results showed a decreasing trend over the last 1000 generations for all breeds, with an increasing slope since about 100 generations ago. The highest historically effective population size in recent generations (5 generations ago) was found in the Arabian breed (53 heads) and the lowest for Caspian and Thoroughbred (33-34 heads) breeds. Generally, the results of this study indicated that despite a reasonable genetic variation and low inbreeding value, however, the Ne is the lowest in Caspian compared to other Asian horse breeds that designing of appropriate programs is necessary to conserve remaining purebred animals of this indigenous Iranian horse breed.

کلیدواژه‌ها [English]

  • Asian horse breeds
  • effective population size
  • inbreeding value
  • run of homozygosity
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