2019 ASHS Annual Conference

Three main commercial types of blueberry are grown for the United States blueberry market. These are northern highbush (NHB, Vaccinium corymbosum L.), rabbiteye (RE, V. virgatum Aiton), and southern highbush (SHB, Vaccinium sp., which is a species complex between V. corymbosum L. and V. darowwi Camp). NHB blueberry types are grown in northern states of the country. The specific role of ethylene and its influence during fruit ripening and postharvest storage of blueberry is still largely debated. The main objective of this study was to investigate if ethylene levels contributed any influence to the performance of fresh postharvest keeping quality characteristics of SHB, RE, and NHB type fruit held in cold storage during a 30 day period. SHB, RE, and NHB blueberries harvested during the 2018 season were used in this study. Fruit were collected from commercial packers representing the early-, mid-, and late- 2018 harvest season from Michigan, Canada, and Georgia. Cultivars included were: seven SHB [‘Star’, ‘Farthing’, ‘Meadowlark’, ‘Legacy’(from GA and MI), ‘Camellia’, ‘Keecrisp’, and 'Suziblue’], five RE (‘Vernon’, ‘Alapaha’, ‘Brightwell’, ‘Powderblue’, and ‘Austin’), and five NHB (‘Bluecrop’, ‘Draper’, ‘Nelson’, ‘Elliott’, and ‘Liberty’). All except ‘Powderblue’, ‘Austin’, and ‘Brightwell’, were hand-harvested. Fruit were kept at 4 °C after collection and processed for a 30 day period at four timepoints (TP): 1) 3-4 days, 2) 10-11 days, 3) 20-21 days, and 4) 30-31 days. Physical characteristics evaluated included: skin strength (puncture-in), and fruit firmness (Kramer shear). Chemical characteristics evaluated include: soluble solids, total titratable acidity, and sugar/acid ratio. A Shimadzu GC 17-A was used to collect ethylene measurements during TP 1. In this evaluation, ethylene measured during TP1 was correlated to physical and chemical fruit characteristics of TP 1 and TP 4 using Pearson’s correlation coefficients. Correlations were also performed between physical and chemical fruit characteristics within each timepoint. Significant differences for all quality characteristics (P≤0.001) were found for types and cultivars within TP1 and TP4. Additionally, ethylene measurements significantly correlated (P≤0.05) to fruit firmness (Kramer Shear) in NHB during TP1, and to skin strength (puncture-in) during TP1 and TP4 for both RE and SHB. This suggests that ethylene may have a close relationship with fruit texture changes in postharvest fresh storage. This information will be used to help growers and breeders select cultivars of high postharvest textural quality, and in the development of breeding tools for the creation of new cultivars with superior postharvest keeping quality.