عوامل موثر بر نتایج انتخاب دو مرحله ای در طرح اصلاح نژادی هسته باز

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دوره دکتری، گروه علوم دامی، دانشکده علوم کشاورزی، دانشگاه گیلان

2 دانشیار گروه علوم دامی، دانشکده علوم کشاوری، دانشگاه گیلان

3 استاد گروه علوم دامی، دانشکده علوم و مهندسى کشاورزى، پردیس کشاورزى و منابع طبیعى، دانشگاه تهران

4 دانشیار گروه علوم دامی، دانشکده کشاورزی، دانشگاه تربیت مدرس

چکیده

هدف این تحقیق بررسی عوامل موثر بر پیشرفت ژنتیکی سالانه ناشی از یک طرح اصلاح نژاد دارای هسته­­باز بود. انتخاب میش­های پایه که برای جایگزینی در هسته تعیین می­شوند طی دو مرحله به ترتیب با استفاده از شاخص انتخاب پایه و شاخص انتخاب هسته انجام ­شد. برای این منظور یک سیستم اصلاح نژاد هسته­­باز با استفاده از اطلاعات جمعیت گوسفندان لری­بختیاری به­روش قطعی شبیه­سازی شد. ابتدا پیشرفت ژنتیکی ناشی از انتخاب دو مرحله­ای در شرایط مبنا برآورد شد و سپس سطوح مختلف صحت انتخاب در پایه و هسته و دو سطح متفاوت از نرخ باروری مدنظر قرار گرفت. در شرایط مبنا، مزیت انتخاب دو مرحله­ای نسبت به انتخاب تک مرحله­ای مبتنی بر شاخص پایه 65/7 درصد بود. در این شرایط همبستگی 627/0 بین شاخص پایه و هسته وجود داشت. مزیت انتخاب دو مرحله­ای به صحت انتخاب در دو مرحله وابسته بود و از 6/4 درصد (صحت انتخاب پایه و هسته به­ترتیب برابر 5/0 و 65/0) تا 45/15 درصد (صحت انتخاب دو مرحله به ترتیب برابر 2/0 و 95/0) تغییر کرد. حداکثر مزیت انتخاب دو­مرحله­ای با نرخ باروری پایین (7/0) و ضریب همبستگی پایین بین شاخص انتخاب دو مرحله (211/0) بدست آمد و برابر با 45/15 درصد بود. به طور کلی نتایج نشان دادند در شرایطی که بین شاخص­های پایه و هسته همبستگی کمتری وجود داشته باشد و درصد باروری پایین باشد مزیت استفاده از انتخاب دو مرحله­ای بیشتر است.

کلیدواژه‌ها

عنوان مقاله [English]

Factors affecting the results of two-stage selection in open nucleus breeding

نویسندگان [English]

  • H. Askari-Hemmat 1
  • A. A. Shadparvar 2
  • S. R. Miraei-Ashtiani 3
  • R. Vaez Torshizi 4
1 Ph. D. Student, Department of Animal Science, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran
2 Associate Professor, Department of Animal Science, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran
3 Professor, Department of Animal Science, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
4 Associate Professor, Department of Animal Science, Faculty of Agriculture, Tarbiat Modarres University, Tehran, Iran
چکیده [English]

The objective of this research was to study the factors affecting the annual genetic gain resulting from an open nucleus breeding system with selection of base-born nucleus replacement ewes in two stages using base and nucleus indices, respectively. For this purpose, an open nucleus breeding system was simulated using a deterministic approach with information from Lori-Bakhtiary sheep population. First, the genetic gain from two-stage selection in basic conditions was estimated. Then, different levels of accuracies in base and nucleus and two different levels of fertility were envisaged. In basic conditions, advantage of two-stage selection over single-stage selection using base index was 7.65 %. Correlation between base and nucleus indices in this situation was 0.627. Advantage of two-stage selection depended on the accuracies of selection in the two stages and varied from 4.6% (with accuracies of base and nucleus of 0.5 and 0.65, respectively) to 15.45% (with accuracies of base and nucleus of 0.2 and 0.95, respectively). Maximum advantage of two-stage selection (15.45%) resulted from low fertiliry rate (0.7) and low correlation (0.211) between indices of the two stages. In general, results showed that with lower correlations of base and nucleus indices and low fertility rates, advantage of two-stage selection is greater.

کلیدواژه‌ها [English]

  • Two-stage selection
  • Deterministic simulation
  • Open-nucleus scheme
  • Lori-Bakhtiari sheep

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