Preventing and detecting sunburn on ‘Ambrosia’ apples

Research Brief Publication Date: May 07, 2024
Last Updated: July 11, 2024
Hao Xu, Yoichiro Watanabe, Danielle Ediger, Xiaotang Yang, and Davis Iritani.


To help producers adapt to the changing climate, this study examined the impact of rootstock size on sunburn browning and assessed the differences in fruit quality between healthy (marketable) 'Ambrosia' apples and those affected by sunburn browning. The results of this study will help with decision making on ‘Ambrosia’ apple rootstock selection and post-harvest sorting. 

Extreme weather events, such as droughts, floods, heat waves, and cold snaps, are predicted to occur more frequently and become more extreme with climate change. Regardless of the crop grown, these events can cause significant losses in crop yield and quality. In the summer of 2021, Interior British Columbia experienced several heat waves with record-breaking temperatures, causing significant damage to apples, including ‘Ambrosia’. This sparked the realization that without understanding the variety’s responses to heat, it’s difficult to predict or accurately assess the impacts of heat and other climate change related stress.

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Moderate sunburn browning on an ‘Ambrosia’ apple after extreme heat in 2021. Photo by Hao Xu.

About this Brief

This brief was prepared by the BC Food Web team with the help of Hao Xu and is based on the following scientific journal article:

Xu, H., Watanabe, Y., Ediger, D., Yang, X., & Iritani, D. (2022). Characteristics of sunburn browning fruit and rootstock-dependent damage-free yield of ambrosia™ apple after sustained summer heat events. Plants, 11(9), 1201.


Key Findings

  • Sunburn browning on apples led to negative fruit qualities such as reduced weight, faster ripening, higher acidity, and faster loss of firmness and worsened weight retention after harvest. 
  • When water supply was sufficient, ‘Ambrosia’ apples on large-dwarfing rootstock Geneva 935 had less heat damage compared to those on small and medium-dwarfing rootstocks. 
  • Handheld DA (delta absorbance) meters, which are usually used to monitor fruit maturation, can also detect moderate sunburn browning in apples.