Accuracy of Genomic Prediction under Different Genetic Architectures and Estimation Methods
محورهای موضوعی : Camelع. عاطفی 1 , ع.ا. شادپرور 2 , ن. قوی حسین-زاده 3
1 - Department of Animal Science, Faculty of Agricultural Science, University of Guilan, Rasht, Iran
2 - Department of Animal Science, Faculty of Agricultural Science, University of Guilan, Rasht, Iran
3 - Department of Animal Science, Faculty of Agricultural Science, University of Guilan, Rasht, Iran
کلید واژه: Accuracy, heritability, QTL, bayesian, genomic, genetic architecture,
چکیده مقاله :
The accuracy of genomic breeding value prediction was investigated in various levels of reference population size, trait heritability and the number of quantitative trait locus (QTL). Five Bayesian methods, including Bayesian Ridge regression, BayesA, BayesB, BayesC and Bayesian LASSO, were used to estimate the marker effects for each of 27 scenarios resulted from combining three levels for heritability (0.1, 0.3 and 0.5), training population size (600, 1000 and 1600) and QTL numbers (50, 100 and 150). A finite locus model was used to simulate stochastically a historical population consisting 100 animals at first 100 generations. Through next 100 generations, the population size gradually increased to 1000 individuals. Then the animals in generations 201 and 202 having both known genotypic and phenotypic records were assigned as reference population, and individuals at generations 203 and 204 were considered as validation population. The genome comprised five chromosomes of 100 cM length and 500 single nucleotide polymorphism markers for each chromosome that distributed through the genome randomly. The QTLs and markers were bi-allelic. In this study, the heritability had great significant positive effect on the accuracy (P<0.001). By increasing the size of the reference population, the average genomic accuracy increased from 0.64±0.03 to 0.70 ± 0.04 (P<0.001). The accuracy responded to increasing number of QTLs non-linearly. The highest and lowest accuracies of Bayesian methods were 0.40 ± 0.04 and 0.84 ± 0.05, respectively. The results showed having the greatest amount of information (i.e. highest heritability, highest contribution of gene action in phenotypic variation and large reference population size), the highest accuracy (0.84) was obtained, with all investigated methods of estimation.
صحت پیش‌بینی ارزش‌های اصلاحی ژنومی در سطوح مختلف اندازه جمعیت مرجع، وراثت‌پذیری صفت و تعداد QTL مورد بررسی قرار گرفت. پنج روش بیزی شامل رگرسیون ریدج بیزی، بیز A، بیز B، بیز C و بیز لزو برای برآورد اثرات نشانگری طی 27 سناریو حاصل از ترکیب سه سطح وراثت‌پذیری (1/0، 3/0 و 5/0)، اندازه جمعیت مرجع (600، 1000 و 1600) و تعداد QTL (50، 100 و 150) مورد استفاده قرار گرفت. یک مدل جایگاه ژنی محدود برای شبیه‌سازی تصادفی یک جمعیت تاریخی شامل 100 حیوان در 100 نسل اول مورد استفاده قرار گرفت. طی 100 نسل بعدی اندازه جمعیت به تدریج به 1000 فرد افزایش یافت. سپس افراد نسل‌های 201 و 202 که دارای اطلاعات ژنوتیپی و فنوتیپی معلوم بودند به عنوان افراد جمعیت مرجع در نظر گرفته شده و نسل 203 و 204 بعنوان جمعیت تأیید لحاظ شدند. ژنوم شامل 5 کروموزوم هر کدام به طول 100 سانتی‌مورگان و 500 نشانگر چند‌شکلی تک نوکلئوتیدی بود که به صورت تصادفی در سطح کروموزوم‌ها توزیع شده بودند. QTLها و نشانگرها دو آللی بودند. در تحقیق حاضر، وراثت‌پذیری اثر معنی‌دار مثبتی بر صحت داشت (001/0P<). با افزایش اندازه جمعیت مرجع میانگین صحت برآورد ژنومی از 03/0 + 64/0 به 04/0 + 70/0 افزایش یافت (001/0P<). صحت برآوردها به صورت غیر خطی به افزایش تعداد QTL عکس العمل نشان داد. بیشترین و کمترین مقدار صحت روش‌های بیزی به ترتیب 05/0 + 84/0 و 04/0 + 40/0 بود. نتایج نشان می‌دهد که داشتن مقدار اطلاعات زیاد (وراثت‌پذیری بالا به عنوان مشارکت بیشتر ژن‌ها در واریانس فنوتیپی و جمعیت مرجع بزرگتر) منجر به صحت‌های بالاتر در تمام روش‌های برآورد استفاده شده می‌شود.
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