Miller, Baylee2021-02-222021-02-222020-12https://hdl.handle.net/11299/218648University of Minnesota M.S. thesis.December 2020. Major: Applied Plant Sciences. Advisor: James Luby. 1 computer file (PDF); viii, 153 pages.Apple fruit acidity and sweetness are two of the major trait components involved in apple seedling sensory evaluation. Published studies have alluded to some of the genetic components of apple fruit acidity and sweetness, but few have included an array of germplasm relevant to the University of Minnesota apple breeding program. With the release and subsequent frequent use of ‘Honeycrisp’ and ‘Minneiska’ apple cultivars as parents at the University of Minnesota, the germplasm set deviates from other breeding programs. In order to increase breeding efficiency and increase overall quality of apple seedlings, this study describes the genetic components of apple fruit acidity and sweetness and provides breeding insights to negate the creation of undesirable apple seedlings. This study uses data from 2010 to 2018 to characterize a wide but relevant array of germplasm, using six major families, three of which have ‘Honeycrisp’ as a parent, and three of which have ‘Minneiska’ as a parent. Three major loci associated with variation in titratable acidity content on linkage groups 1, 8, and 16, and two loci associated with variation in soluble solids content on linkage groups 1 and 13 were identified, and haplotypes were characterized for each locus. The conclusions from this study provide insights for designing crosses that create seedlings with desirable ranges of acidity and sweetness characteristics.enAcidAppleBreedingGeneticsQTLSugarThesis or Dissertation