Fruit Trait Phenotypic Dataset for RosBREED Apple Reference Germplasm Set, Poster Board #425

Marker-assisted breeding is facilitated by marker-locus-trait associations validated in germplasm relevant to a particular breeding program. Establishing these associations depends on having an extensive, reliable phenotype database for traits of interest in this germplasm.  A reference apple germplasm set of 496 individuals including cultivars, selections, and seedlings was identified as part of the USDA-SCRI RosBREED project. The germplasm set provides allelic representation of historic and current parents in RosBREED demonstration apple breeding programs at Cornell University (CU), Washington State University (WSU), and the University of Minnesota (UMN).  Phenotyping at the three locations was conducted according to standardized protocols that specified fruit harvest maturity and focused primarily on fruit traits evaluated at harvest and following 10 and 20 weeks of refrigerated storage. Descriptive statistics for phenotypic data at harvest only are reported for two years on 3 internal traits, 15 external traits, 7 sensory traits, 3 chemistry analyses, and 17 instrumental measurements (Mohr Digi-Test (MDT) and Effigi penetrometer).  The number of individuals phenotyped at harvest varied each year with 215 genotypes evaluated in 2010 and 330 genotypes evaluated in 2011.  A total of 413 unique genotypes were evaluated over both years.  As each location had a largely unique set of individuals as well as differing environmental conditions, means, ranges and phenotypic variances for traits varied greatly among location subsets for some traits [diameter 2010, bitter pit 2010, pH 2010, weight 2011, soluble solids (°Brix) 2010, sensory sweetness 2011, MDT crispness (Cn) 2010 and 2011, MDT firmness at the core boundary (E2) 2010 and 2011, MDT firmness in region 2 (M2) 2010 and 2011, and MDT quality factor (QF) 2010 and 2011].   Other traits were quite similar across locations [pH 2011, sensory sweetness 2010, titratable acidity 2010 and 2011, soluble solids 2011, and MDT maximum firmness in region 1 (M1) 2010].  Year-to-year repeatability at a location, however, was generally moderate to high for Pearson’s correlation coefficients for most traits (UMN = 0.36 < r < 0.75,  WSU = 0.34 < r < 0.80, and Cornell = 0.30 < r < 0.90).  Phenotypic data for the RosBREED apple reference germplasm set are curated and available for use by community breeders and other scientists in the Breeders Toolbox at the Genome Database for Rosaceae (www.rosaceae.org).