2019 ASHS Annual Conference

Solar stress contributes to quality loss prior to harvest of many fruit species including apples, European pears, and sweet cherries. However, the impact following harvest can be less evident, ranging from overt appearance defects developing throughout the cold chain to less obvious quality loss or lot inconsistency. As climates in many temperate production regions of these crops are projected to continue warming, it is likely that quality defects related to solar stress will become even more prevalent. Sunscald, lenticel blotch, and cracking are examples of postharvest disorders that develop during the cold chain and are caused or exacerbated by direct sunlight and, potentially, air temperature, sometimes in combination with chilling stress. Fruit canopy position or even aspect with respect to sun exposure can also influence ripening and other quality phenotypes in part related to heat gradients contributed by shading. As may be expected, many of these phenotypic differences can be linked with metabolic changes during storage. In fact, metabolic differences resulting from differential sun exposure point to multiple pathways indicating influences on both physiology and structure and the considerable contribution sun exposure may have to inconsistency of quality and ripeness, even within a single tree. It also reveals potential solutions using these differences as bases for mitigating quality loss caused by differential sunlight exposure. Common pathways influenced by sunlight during storage, postharvest phenotypes impacted, and harvest and storage management opportunities using metabolic differences will be discussed.