Distance-based exclusion method for parentage analysis using microsatellites (SSR) markers

Genotyping mistakes represent a challenge in parental assignment where even small errors can lead to significant amounts of unassigned siblings. Different parental assignment algorithms have been designed to approach this problem. The Exclusion method is the most applied for its reliability and biological meaning. However, the resolving power of this method is the lowest for data containing genotyping errors. We introduce a new distance-based approach which we coin as Distance-Based Exclusion (DBE). The DBE method calculates the distance between the offspring haplotype and haplotype of each of the potential fathers. The father with the lowest distance is then assigned as candidate father according to a distance ratio (). We have tested the Exclusion and DBE methods using a real dataset of 1230 offsprings subdivided into families of 25 individuals. Each family had six potential fathers and one known mother. Compared with the Exclusion method, the DBE method is able to solve 4.7% more individuals (64.4% Exclusion vs 69.1% DBE) using the most restrictive tested without errors. DBE method can also be used together with the Exclusion method for error calculation and to further solve unassigned individuals. Using a two-step approach, we were able to assign 98.1% of the offsprings with a total predicted error of 4.7%. Considering the results obtained, we propose the use of the DBE method in combination with the Exclusion method for parental assignment.