Abstract
Cross-species hybridizations have been extensively used to generate animals and plants better suited for draft and food and fiber production since Roman times, and are still important in current agricultural practices with growing uses especially in aquaculture. Diagnostic tools based on marker panels with sufficient numbers of markers for accurate identification of cross-species hybrid individuals from intercrossed and backcrossed populations are increasingly necessary for practical, accurate species-purity certification and management of commercial broodstocks. Minimal numbers of di-allelic markers with species-specific alleles required to accurately identify hybrid individuals in intercrossed and advanced backcrossed populations were estimated using power analysis, and ranged from 5 to 191 (α = .05), and from 7 to 293 (α = .01), considering backcross 1 (BC1) to BC6 populations, respectively. Numbers of markers required for accurate hybrid identification observed in simulated BC1 to BC6 populations ranged from 5 to 1,131 and 7 to 8,065, considering error rates ≤ 5% and ≤ 1%, respectively. Estimated and observed numbers of diagnostic markers required for accurate hybrid identification up to four generations of backcrossing fall within practical operational limits of most commercial platforms currently available for genotyping low-density SNP marker panels. Therefore, cost-effective assay panels could be developed to provide practical tools for accurate species-purity certification.
Highlights
Artificial production of cross-species hybrids has been extensively used to generate animals and plants better suited for a diversity of uses such as draft and production of food and fiber since ancient Roman times (Adams et al, 2007), and still plays an important role in current agricultural practices, with growing use especially in aquaculture
An extreme situation was considered where every nucleotide could be considered a potential diagnostic marker, and 30 generations of backcrossing an F1 hybrid would be required for the expected number of base-pairs from a non-target species to be
Numbers of required markers for correct hybrid identification estimated and simulated show that a minimum of four or seven independently-segregating nuclear bi-allelic markers with species-specific alleles are required for accurate individual hybrid identification in F2 and backcross 1 (BC1) populations, respectively, considering false positive (a) error rates
Summary
Artificial production of cross-species hybrids has been extensively used to generate animals and plants better suited for a diversity of uses such as draft and production of food and fiber since ancient Roman times (Adams et al, 2007), and still plays an important role in current agricultural practices, with growing use especially in aquaculture. F1 hybrids are expected to perform better in captive production systems in respect to productivity and quality traits, as a consequence of the resulting positive heterosis, in spite of the lack of solid studies in many instances to accurately contrast production performances of hybrid populations with parental species (reviewed by Hashimoto et al, 2012). Once unknown introgressions have occurred in captive broodstocks, expected results from genetic improvement programs established to breed fish with better productivity and quality traits may become unknowingly compromised, especially because observed high fecundity rates can act to rapidly disseminate introgressed germplasm
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