Physiological Adaptation Capacities of Three Southern Highbush Blueberry (Vaccinium corymbosum L.) Cultivars to Çukurova Conditions

This study investigated the physiological performance of three highbush blueberry cultivars ('Star', 'Legacy', 'Biloxi') grown under the climate of the Çukurova region in southern Türkiye. Plants were grown in 30 L containers under a hail-net structure, and measurements were made at flowering, early fruit set and peak harvest. Principal physiological characteristics such as net photosynthesis, stomatal conductance, transpiration, leaf temperature, SPAD chlorophyll index and maximum PSII efficiency (Fv/Fm) were measured to identify cultivar specific responses to progressive increases in temperature and VPD. A consistent separation among cultivars emerged as environmental demand increased. 'Star' kept the highest photosynthetic activity, strongest stomatal response, and lowest leaf temperatures, with relatively stable Fv/Fm through the season. 'Legacy' had moderate resilience, largely through sustained chlorophyll levels, while 'Biloxi' was sensitive, reflected in higher leaf temperatures, lower PSII efficiency, and accelerated pigment decline. Overall, this study underlines the key role of cultivar choice in maintaining physiological stability in warm blueberry growing regions, pointing out 'Star' as a particularly suitable genotype for environments facing increasing thermal and evaporative stress