Phenotyping Protocol for Sweet Cherry (Prunus avium L.) to Enable an Understanding of Trait Inheritance

The USDA Specialty Crop Research Initiative-funded RosBREED project has the objective of enabling marker-assisted breeding (MAB) in the economically important agricultural family of the Rosaceae. To standardize and increase the accuracy of MAB in Rosaceae, it is necessary to characterize many horticultural and fruit quality traits in representative germplasm. A well-developed comprehensive phenotyping protocol for productivity traits, fruit quality traits and horticulturally objectionable traits, developed for use in the Washington State University (WSU) Sweet Cherry Breeding Program, is described and selected correlations among traits observed and quantified. The protocol facilitates standardization of data among researchers working with sweet cherry across various environments and institutions. Data collected from sweet cherry ‘Crop Reference Set’ and ‘Breeding Pedigree Set’ between 2010 and 2012 was evaluated for correlation among sweet cherry phenotypic traits, and the results are presented. Selected results indicate significant moderate correlations for harvest date with fruit weight and fruit firmness (r=0.26, p<0.0001 and r=0.39, p<0.0001, respectively), with later- maturing varieties tending towards larger and firmer cherries, in general. Also, fruit weight had a positive significant association with pedicel-fruit retention force with r=0.43 (p<0.0001). However, soluble solid content showed a negative relationship with fruit weight and firmness (r=-0.34 and r=-0.20, respectively). Progress in breeding for multiple traits simultaneously will be faster with the significant positive correlations obtained in this study.