Genomic prediction for polysomic tetraploid potato inbred and hybrid offspring

Abstract Potato genetic improvement begins with crossing cultivars or breeding clones -often having complementary characteristics– for producing heritable variation in segregating offspring, in which phenotypic selection is used thereafter across various vegetative generations (Ti). Multi-environment, multi-trait, tetrasomic genomic best linear unbiased predictors (GBLUPs) have the potential to identify promising parents for further crossing, predict untested environments or genotypes, or purge deleterious alleles in inbred potato populations. Hence, the aim of this research was to determine whether GBLUPs may predict tuber yield across early Ti within and across breeding sites in inbred (S1) and hybrid (F1) tetraploid potato offspring. This research used 858 breeding clones for a T1 trial at Umeå in 2021, as well as 829 and 671 clones from the breeding population for T2 trials during 2022 at Umeå (Norrland) and Helgegården (Skåne), in northern and southern Sweden respectively, along with their parents (S0) and check cultivars. The S1 and F1 derived from selfing and crossing four S0. The experimental layout was an augmented design of 4-plant plots in the three breeding sites, in which breeding clones were non-replicated and the parents and cultivars were in all blocks in between the former. Genomic prediction ability (r) for tuber weight per plant were 0.5944 and 0.6776 in T2 at Helgegården and Umeå, respectively, when T1 at Umeå was the training population. On average, r was larger in inbred than in hybrid offspring at both breeding sites. There were significant differences for r among half-sib F1 offspring at Helgegården, and among S1 at both Helgegården and Umeå. The r was also estimated using multi-environment data (involving at least one S1 and one F1) for T2 performance at both breeding sites. The r was strongly influenced by the genotype in both S1 and F1 offspring irrespective of the breeding site. GBLUPs are therefore useful for selecting breeding clones with different inbreeding levels in early stages.