Optimization of crossing strategy based on the usefulness criterion in interpopulation crosses considering different marker effects among populations.

key messageHerein, a method has been proposed for selecting optimal cross pairs based on the genetic potential of progeny in interpopulation crosses, considering different genetic effects among populations. In the breeding programs for self-pollinating plants, genetic improvements in multiple traits can be challenging when relying solely on a single biparental population, and interpopulation crosses are employed to integrate favorable alleles from multiple biparental populations to overcome this limitation. In this context, it is crucial to consider distinct genetic effects in different populations. In this study, we used a selection method based on the usefulness criterion (UC) to identify cross pairs suitable for interpopulation crosses. We expanded this approach to enhance breeding programs by accounting for varying genetic backgrounds within the genomic selection framework. Using the medicinal plant perilla as the study material, we performed simulations to compare the efficacy of selection based on the estimated genotypic values with that of selection based on UC. Our findings demonstrate that the proposed method is effective in facilitating the simultaneous improvement of multiple traits, particularly by considerably increasing the genetic gains among the top-performing individuals in the population. Furthermore, we provide guidelines for implementing interpopulation crosses, including recommendations for the optimal generation for crossing and an appropriate reference generation for calculating UC. The results obtained in this study offer valuable insights for small-scale breeding programs aimed at simultaneously enhancing multiple traits through interpopulation crosses and can be applied to a wide range of crops, including neglected and underutilized species.