Variation In Pedicel-Fruit Retention Force In Sweet Cherry

Successful mechanical or mechanically-assisted sweet cherry (Prunus avium L.) harvest requires a low retention force between the fruit and pedicel. A considerable range exists for pedicel-fruit retention force (PFRF) among sweet cherry cultivars but there are no reports on PFRF of new sweet cherry hybrids nor the relationship between PFRF and fruit quality attributes. To enable the adoption of future harvest technologies it is necessary to identify genotypes that combine low PFRF with excellent fruit quality. This study was designed to characterize the PFRF of current commercial sweet cherry cultivars and hybrid seedlings, and determine the relationship between PFRF and fruit quality. Experiments were conducted during 2009 and 2010, at the Washington State University Irrigated Agriculture Research and Extension Center. A total of 19 cultivars and 12 hybrid seedlings were sampled in 2009 and 29 cultivars and 19 hybrids were assessed in 2010. Genotypes were screened at commercial maturity starting from June of each year. PFRF and stem length were recorded in the field, whereas fruit quality parameters including weight, size, exocarp color, firmness, titratable acidity (TA) and SSC were assessed within 24 hours of harvest in the lab. The frequency of PFRF in sweet cherry cultivars and hybrids displayed continuous distribution, suggesting that this is a quantitative trait. The effects of genotype and year were significant as well as the interaction between genotype × year (p<0.0001). This highlights the importance of both genetics and environment on PFRF. The significantly lower (p<0.0001) mean PFRF of hybrids (0.71kg/f) compared to their parents and/or commercial cultivars (0.92kg/f) suggests that PFRF can be improved upon through breeding. Correlations between PFRF and fruit quality attributes were generally low (correlation coefficients of -0.163 to 0.175), suggesting that PFRF has minimal influence on fruit quality. Sweet cherry hybrids and cultivars with low PFRF and good fruit quality have been identified as candidates for further testing while we will continue to improve on PFRF through breeding.