Fruit canopy positioning affects fruit calcium and potassium concentrations, disorder incidence, and fruit quality for ‘Honeycrisp’ apple

Authors: KALCSITS, LEE - Washington State University; Mattheis, James; GIORDANI, LUCA - Washington State University; REID, MICHELLE - Washington State University; MULLIN, KATIE - Washington State University

Submitted to: Canadian Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2019
Publication Date: 6/27/2019
Citation: Kalcsits, L., Mattheis, J.P., Giordani, L., Reid, M., Mullin, K. 2019. Fruit canopy positioning affects fruit calcium and potassium concentrations, disorder incidence, and fruit quality for ‘Honeycrisp’ apple. Canadian Journal of Plant Science. 99(5): 761-771. https://doi.org/10.1139/cjps-2019-0017.
DOI: https://doi.org/10.1139/cjps-2019-0017

Interpretive Summary: Apple fruit are available year-round in most domestic supermarkets. For fruit grown in the USA, this availability period is primarily due to cold storage technologies that slow fruit ripening and extend the time over which fruit quality is acceptable for retail marketing. One factor that can limit retail acceptability is development of fruit disorders during storage that impact fruit appearance or internal quality. These disorders may be dark spots on the peel or brown areas in the fruit interior. Risk of some of these disorders may be preordained by conditions on the tree during fruit development. Knowing what factors determine disorder risk allows management both pre- and postharvest to reduce the potential loss of fruit. This study was designed to determine if the part of the tree (top, bottom, inside, outside) where apples are grown influences postharvest disorder risk for the popular variety ‘Honeycrisp’. Results indicated fruit position on the tree has a big influence on disorders that develop during storage and suggests segregation of fruit at harvest by on-tree position during growth may assist industry in marketing to avoid loss of fruit to disorders.

Technical Abstract: One advantage of high-density orchard systems is homogeneity in fruit maturity and quality. However, even in modern orchard systems, variation in fruit quality may occur. ‘Honeycrisp’ apple is susceptible to numerous disorders including bitter pit, soft scald, and poor color development. Heterogeneity in fruit quality and nutrient distribution can lead to variation in fruit storability. Here, we sought to determine the within-canopy variation in calcium and potassium concentrations, quality, and disorder development for fruit across nine representative orchards. Calcium was more affected by canopy position than potassium; calcium concentrations were greater in the upper part of the canopy than lower. The inverse was true for potassium, but the differences were much smaller. This variation was significantly correlated with mean bitter pit incidence, which was between 20 and 30% in the lower half of the tree and less than 15% in the upper half. Fruit quality was significantly affected by the position in the canopy and was not constrained to only color but also other quality metrics such as dry matter, size, and firmness. Additionally, the internal ethylene concentrations (IEC) of fruit in the upper canopy were approximately 50% of the IEC for fruit from the lower canopy. With an increased emphasis on uniformity and predictability of fruit for long-term storage, these results underscore the importance of understanding variation within the canopy. Even for high density systems, significant variation in fruit quality can occur and spatial segregation could improve storability of high-quality fruit harvested from the upper canopy.