Evaluating drought tolerance of southern highbush and rabbiteye blueberries

Abstract

Drought is one of the most detrimental natural causes leading to yield loss in crops across the globe. With increasing severity and frequency of drought events, it is imperative to identify and breed for cultivars that can withstand periods of water deficit. In blueberry (Vaccinium sp.), drought is especially adverse due to a shallow root system which lacks root hairs. The purpose of this study was to identify common responses of blueberry to drought in addition to finding cultivars with superior traits in response to water deficit. In the southeastern United States, both rabbiteye (Vaccinium virgatum) and southern highbush (Vaccinium corymbosum L. interspecific hybrids) blueberries are commonly cultivated due to their low chill requirements. Previous studies have highlighted on the ability of the rabbiteye ecotype to withstand several abiotic stresses including drought, while southern highbush is more well-known for its superior berry quality.

In order to examine the effects of drought on both southern highbush and rabbiteye blueberries, seven cultivars were chosen for evaluation: Misty, Star, Suziblue (SHB), Brightwell, Vernon, Powderblue, and Climax (RE). Four-year-old plants of all seven cultivars were subjected to a drought period of 36-days in the spring of 2023 at EV Smith Research Station in Tallassee, AL. Throughout the drought, plants were monitored for overall plant health, physiological activity, yield, and fruit quality.

Drought stress was found to significantly decrease photosynthesis, stomatal conductance, electron transport rate, leaf relative water content, specific leaf area, chlorophyll content, Jmax, yield, average berry weight, and malic acid content of berries. Alternatively, water stress was found to significantly increase Brix, polyphenol, and berry firmness. Star and Misty were identified as the most drought tolerant cultivars based on high yield and average berry weight in addition to high levels of gas exchange under drought stress. Alternatively, Powderblue, Vernon, and Suziblue were found to be the most susceptible to drought. Brightwell was found to have intermediate tolerance in comparison to other cultivars. In the future, it would be valuable to study post-drought root morphology in addition to studying genetic factors that may play a role in blueberry drought tolerance