Simple sequence repeat markers linked to the everbearing flowering gene in long-day and day-neutral cultivars of the octoploid cultivated strawberry Fragaria × ananassa

To identify markers closely linked to the everbearing gene in the octoploid cultivated strawberry Fragaria × ananassa, we conducted linkage analysis based on simple sequence repeat (SSR) polymorphisms. We analyzed F1 populations from three crosses: ‘Sagahonoka’ × ‘Summer-berry’ (94 individuals), ‘Sagahonoka’ × ‘Ever-berry’ (137 individuals), and ‘Hecker’ × ‘Sagahonoka’ (177 individuals). ‘Sagahonoka’ is a June-bearing cultivar; ‘Summer-berry’ and ‘Ever-berry’ are everbearing cultivars classified as older everbearers with a long-day flowering response; ‘Hecker’ is a day-neutral cultivar having F. virginiana ssp. glauca in its ancestry. In these populations, the closest marker, FxaACA02I08C, was mapped at 1.1 cM (‘Summer-berry’ and ‘Hecker’) or 1.5 cM (‘Ever-berry’) from the everbearing gene. We detected correspondence between SSR allele segregation and the flowering habit: one allele was linked to the everbearing trait and the other one to the June-bearing trait. The concordance between the phenotype and marker genotype was more than 98 % in all three populations. These results indicate that the everbearing trait is regulated by a single dominant gene. We also conclude that the locus regulating the everbearing or June-bearing flowering habit is the same in long-day and day-neutral types. The identified markers will be useful for the selection of progeny of various everbearing cultivars.