Faba bean populations already contain the inbreds needed for breeding

Producing inbred lines in faba bean ( Vicia faba L.) breeding is, although crucial, a long, costly and laborious process due to the partial allogamy of the crop. However, in any genetically diverse and open pollinating faba bean population, this particular reproduction system leads to the so-called Identity Disequilibrium, resulting in a significant proportion of individuals being highly inbred. This study presents a cost-efficient approach to identify these highly inbred individuals from populations with a limited number of KASP markers. We found that 8.4% of individuals of the “Göttingen Winter Bean Population” were highly inbred. Using simulations, the most accurate inbreeding coefficient estimator from limited number of markers (ten to 100) was found to be the so-called estimator F _L (which is based on a maximum likelihood approach). Our results allowed to explore the appropriate inbreeding coefficient value to be used as threshold to classify individuals as highly inbred, which optimizes the performance of our approach. Using 50 markers and taking 0.9 as inbreeding classification threshold, we identified 36 truly highly inbred individuals, along with six not-enough-inbred individuals (false positives) in our population. Using a low number of markers in a preliminary step to eliminate not-enough-inbred individuals, successfully permitted a significant and marked reduction of genotyping cost (up to 46%). Faba bean breeders can greatly benefit from the presented approach by identifying highly inbred individuals fast, at low cost and with limited labor, even though no DH technology is available.