Determining minimum numbers of di-allelic diagnostic markers required to identify introgressions in diploid cross-species hybrid individuals from different types of inter- and backcross populations.

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.