Apple Fruit Size QTLs on Chromosomes 8 and 16 Characterized in ‘Honeycrisp’-Derived Germplasm

Abstract

Multiple quantitative trait loci (QTLs) associated with fruit size have been reported in apple (Malus domestica Borkh.); however, few have been fully characterized and/or validated. A pedigree-based QTL analysis approach was used to examine the genetic basis of fruit weight in ‘Honeycrisp’-derived germplasm. Fourteen breeding parents were represented by 814 offspring from 13 full-sib families with breeding parents ‘Honeycrisp’ and ‘Minneiska’ being highly represented. Historical fruit weight data and curated genome-wide single nucleotide polymorphism (SNP) data were leveraged to map QTLs to chromosomes (Chrs) 8 and 16, which together accounted for 15% of the phenotypic variation. The Chr 16 QTL colocalized with other important Chr 16 trait loci. ‘Honeycrisp’ inherited two low fruit weight haplotypes at the Chr 8 QTL from progenitors ‘Northern Spy’ and ‘Grimes Golden’. At the Chr 16 QTL, ‘Honeycrisp’ inherited a low fruit weight haplotype from ‘Frostbite’ and a high fruit weight haplotype from ‘Duchess of Oldenburg’. The small-fruited ‘Honeycrisp’ progenitor ‘Frostbite’ had three low fruit weight haplotypes across the two QTLs. Non-additive interactions were observed at and across QTLs. Results will enable more informed parent selection and/or development of trait-predictive DNA tests for use in apple breeding programs.