QTL discovery and validation for soluble solids content, titratable acidity and remontancy within RosBREED strawberry germplasm

Strawberry is the most consumed Rosaceae small fruit in the world where flavor is a key for the success of a new cultivar. Overall flavor in strawberry is driven by a balance between sugars, acids, and several aroma compounds. Strawberry breeders are interested in using marker-assisted selection to combine better flavor with remontancy (day-neutrality). While quantitative trait loci (QTLs) have been reported for some of these traits, markers do not exist for routine application in breeding. The RosBREED project is focused on enabling marker-assisted breeding via identification and validation of traits important to strawberry breeders. The development of the first genome-wide scanning platform (Affymetrix Axiom IStraw90TW) for the cultivated octoploid strawberry enabled high-throughput genotyping of 384 pedigree-connected strawberry accessions. Phenotypic data for titratable acidity (TA), soluble solids content (SSC) and remontancy were collected in the field in 2011 and 2012 in Oregon and Michigan. FlexQTL™ software was used for a marker consistency check and genome-wide QTL analysis for these three traits using SNP markers that were already genetically positioned using a ‘Holiday’ × ‘Korona’ linkage map. The preliminary QTL analysis resulted in 2 QTLs for TA, 1 QTL for SSC and 7 QTLs for remontancy. These results validate some of the previously reported QTLs. Estimation of haplotype effects and phenotypic variation explained by these QTLs is in progress for RosBREED strawberry germplasm. Haplotypes associated with desirable QTL alleles should enable the development of DNA-based markers and improve efficiency in the development of remontant and flavorful strawberry cultivars.