Diurnal High Temperatures Affect the Physiological Performance and Fruit Quality of Highbush Blueberry (Vaccinium corymbosum L.) cv. Legacy

Abstract

In this study, the physiological performance and fruit quality responses of the highbushblueberry (Vaccinium corymbosum) cultivar Legacy to high temperatures (HTs) were evaluated in afield experiment. Three-year-old V. corymbosum plants were exposed to two temperature treatmentsbetween fruit load set and harvest during the 2022/2023 season: (i) ambient temperature (AT) and(ii) high temperature (HT) (5 °C ± 1 °C above ambient temperature). A chamber covered with transparentpolyethylene (100 μm thick) was used to apply the HT treatment. In our study, the diurnaltemperature was maintained with a difference of 5.03 °C ± 0.12 °C between the AT and HT treatments.Our findings indicated that HT significantly decreased CO2 assimilation (Pn) by 45% andstomatal conductance (gs) by 35.2% compared to the AT treatment. By contrast, the intercellular CO2concentration (Ci) showed higher levels (about 6%) in HT plants than in AT plants. Fruit qualityanalyses revealed that the fruit weight and equatorial diameter decreased by 39% and 13%, respectively,in the HT treatment compared to the AT treatment. By contrast, the firmness and total solublesolids (TSS) were higher in the HT treatment than in the AT treatment. Meanwhile, the titratableacidity showed no changes between temperature treatments. In our study, Pn reduction could beassociated with stomatal and non-stomatal limitations under HT treatment. Although these findingsimprove our understanding of the impact of HTs on fruit growth and quality in V. corymbosum,further biochemical and molecular studies are need.