Comparing genomic signatures of selection between the Abbassa Strain and eight wild populations of Nile tilapia (Oreochromis niloticus) in Egypt

Nayfa, Maria G., Jones, Dave B., Benzie, John A.H., Jerry, Dean R., and Zenger, Kyall R. (2020) Comparing genomic signatures of selection between the Abbassa Strain and eight wild populations of Nile tilapia (Oreochromis niloticus) in Egypt. Frontiers in Genetics, 11. 567969.

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Abstract

Domestication to captive rearing conditions, along with targeted selective breeding have genetic consequences that vary from those in wild environments. Nile tilapia (Oreochromis niloticus) is one of the most translocated and farmed aquaculture species globally, farmed throughout Asia, North and South America, and its African native range. In Egypt, a breeding program established the Abbassa Strain of Nile tilapia (AS) in 2002 based on local broodstock sourced from the Nile River. The AS has been intensively selected for growth and has gone through genetic bottlenecks which have likely shifted levels and composition of genetic diversity within the strain. Consequently, there are questions on the possible genetic impact AS escapees may have on endemic populations of Nile tilapia. However, to date there have been no genetic studies comparing genetic changes in the domesticated AS to local wild populations. This study used 9,827 genome-wide SNPs to investigate population genetic structure and signatures of selection in the AS (generations 9–11) and eight wild Nile tilapia populations from Egypt. SNP analyses identified two major genetic clusters (captive and wild populations), with wild populations showing evidence of isolation-by-distance among the Nile Delta and upstream riverine populations. Between genetic clusters, approximately 6.9% of SNPs were identified as outliers with outliers identified on all 22 O. niloticus chromosomes. A lack of localized outlier clustering on the genome suggests that no genes of major effect were presently detected. The AS has retained high levels of genetic diversity (Ho_All = 0.21 ± 0.01; He_All = 0.23 ± 0.01) when compared to wild populations (Ho_All = 0.18 ± 0.01; He_All = 0.17 ± 0.01) after 11 years of domestication and selective breeding. Additionally, 565 SNPs were unique within the AS line. While these private SNPs may be due to domestication signals or founder effects, it is suspected that introgression with blue tilapia (Oreochromis aureus) has occurred. This study highlights the importance of understanding the effects of domestication in addition to wild population structure to inform future management and dissemination decisions. Furthermore, by conducting a baseline genetic study of wild populations prior to the dissemination of a domestic line, the effects of aquaculture on these populations can be monitored over time.

Item ID: 65933
Item Type: Article (Research - C1)
ISSN: 1664-8021
Keywords: domestication, natural population, population genetics, population structure, outlier analysis, selection, farm management, aquaculture
Copyright Information: Copyright © 2020 Nayfa, Jones, Benzie, Jerry and Zenger. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Funders: European Commission (EC), International Fund for Agricultural Development (IFAD), United States Agency for International Development (USAID), CGIAR Research Program on Livestock and Fish Agri-Food Systems (LIVESTOCK AND FISH), CGIAR Research Program on Fish Agri-Food Systems (FISH) led by WorldFish, Fisheries Society of the British Isles (FSBI), CGIAR Trust Fund
Projects and Grants: EC-IFAD Grant Number 2000001539
Date Deposited: 03 Feb 2021 05:32
FoR Codes: 30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3005 Fisheries sciences > 300501 Aquaculture @ 50%
30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3005 Fisheries sciences > 300504 Fish physiology and genetics @ 50%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8301 Fisheries - Aquaculture > 830102 Aquaculture Fin Fish (excl. Tuna) @ 100%
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