Inbreeding effects on the performance and genomic prediction for polysomic tetraploid potato offspring grown at high Nordic latitudes

Abstract Background. Inbreeding depression (ID) is caused by an increased homozygosity in the offspring after selfing. Although the self-compatible, highly heterozygous, tetrasomic polyploid potato (Solanum tuberosum L.) suffers from ID, some argue that the potential genetic gains from using inbred lines in a sexual propagation system of potato are too large to be ignored. The aim of this research was to assess the effects of inbreeding in potato offspring performance under a high latitude and the accuracy of genomic prediction of breeding values (GEBV) for further use in selection. Results. There were 16 parents (6 breeding clones and 10 cultivars) used in the crossing block. Four of them underwent selfing producing 113 ± 42 S1 seeds, while the seed set in the F1 hybrid offspring was 149 ± 29, suggesting inbreeding did not affect the crossing outcome but may have influenced the seed set. Four inbred (S1) and two hybrid (F1) offspring, and their parents (S0) were used in the experiment, with a field layout of an augmented design with the four S0 replicated in nine incomplete blocks comprising 100, 4-plant plots at Umeå (63°49′30″N 20°15′50″E), Sweden. The S0 was significantly (P < 0.01) better than both S1 and F1 offspring for tuber weight (total and according to five grading sizes), tuber shape and size uniformity, tuber eye depth and reducing sugars in the tuber flesh, while the F1 was significantly (P < 0.01) better than S1 for all tuber weight and uniformity traits. Some F1 hybrid offspring (15–19%) had better total tuber yield than the best performing parent. The GEBV accuracy ranged from -0.3928 to 0.4436. Overall, tuber shape uniformity had the highest GEBV accuracy, while tuber weight traits exhibited the lowest. The F1 full sib’s GEBV accuracy was higher, on average, than that of the S1. Conclusion. Accuracy estimates suggest a non-related training population (either S1 or F1) should not be used for early stages of genomic selection in potato breeding population. Genomic prediction may facilitate eliminating undesired inbred or hybrid offspring for further use in the genetic betterment of potato.