Respiratory activity of ‘Chelan’, ‘Bing’ and ‘Selah’ sweet cherries in relation to fruit traits at green, white-pink, red and mahogany ripening stages

• Sweet cherry fruit development is sub-divided into four stages based on skin color.
• Cultivars have similar respiration patterns albeit different abscission responses.
• Respiratory rate is higher in the earlier ripening cultivar at maturity.
• Both pedicel retention force and fruit firmness peak at the white-pink stage.
• Respiration rates decrease as PFRF decreases and fruit size, SSC and TA increase.

Sweet cherry fruit development is subjectively sub-divided into four stages on the basis of exocarp color, which includes green, white-pink, red and mahogany stages. ‘Chelan’, ‘Bing’ and ‘Selah’, representing early-, mid- and late-season cultivars, respectively, and three different abscission-responses, were selected to explore the relationships between respiratory activity, fruit quality attributes, and pedicel-fruit retention force (PFRF) at the four developmental stages. Respiratory rate was higher in the early ripening cultivar (‘Chelan’) than in the mid- or late ripening cultivars at maturity. However, the cultivars showed similar respiration patterns with a rapid decline of respiration at the green stage followed by a gradual decline, irrespective of abscission behavior or ripening date. A small respiratory peak was observed from the end of the green stage to the beginning of the white-pink stage. Firmness and pedicel retention force (the force required to break the stem and to separate the stem from the fruit) were positively correlated at all stages of fruit development; however, these attributes were negatively correlated with fruit size, particularly at the white-pink and mahogany stages. Also, both firmness and pedicel retention force were greatest at the transition of green and white-pink stages. Fruit respiration rate increased as PFRF increased and decreased as fruit weight, size, soluble solids content (SSC) and titratable acidity (TA) increased in all three cultivars.