Blueberries (Vaccinium sect. Cyanococcus) are prone to drought due to their shallow root system and limited ability to uptake water from the soil. Previous research has shown rabbiteye (Vaccinium virgatum) blueberries to be more tolerant than highbush varieties (Vaccinium corymbosum L.) to abiotic stresses. However, little is known about their response to drought and whether there are ecotype- or cultivar-specific responses. In order to breed for more drought-tolerant cultivars, this study aims to identify drought tolerant mechanisms within existing cultivars of both southern highbush (SHB) and rabbiteye (RE) blueberries. We evaluated seven cultivars of southern highbush and rabbiteye blueberry for physiological response and fruit quality characteristics under water deficit and recovery across two consecutive years. Overall, drought was found to decrease photosynthesis, stomatal conductance, electron transport rate, leaf relative water content, specific leaf area, chlorophyll content, maximum rate of Rubisco carboxylation (Vcmax) and maximum rate of RuBP regeneration (Jmax). Additionally, drought treatment was found to significantly decrease yield and average berry weight while increasing total soluble solids and berry firmness. Misty (SHB) was identified as the most drought tolerant cultivar due to maintenance of CO2 assimilation, stomatal conductance, and yield under drought conditions across both years, while Suziblue (SHB), Powderblue (RE), and Vernon (RE) were found to be more sensitive to water deficit. Star (SHB) was tolerant of drought in the short term but performed worse under repeated drought events.
