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Dormancy of Floral Buds of Rabbiteye Blueberry in a Mild Winter Climate


This work studies the dormancy dynamics of blueberries growing in mild winter regions.

The four rabbiteye blueberry cultivars meet the chilling requirements in the study.

The floral buds of 'Delite' are more precocious than the other cultivars.

Insights on how temperate fruit species could behave in warming climate scenarios.


Blueberry is an important fruit crop, with many health benefits. Despite its importance, much remains to be studied concerning the dormancy dynamics in rabbiteye cultivars growing in a mild winter climate. In this research, the dormancy in blueberry, rabbiteye cultivars ‘Bluegem’, ‘Climax’, ‘Delite’, and ‘Powderblue’, was studied in a mild winter region. The single-node cuttings biological test and the evaluation of the hydric status were performed in dormant winter reproductive buds. These experiments were performed during fall and winter in one year (2016). Moreover, chilling hours under or equal to 7.2 ºC were measured, and chill units were calculated according to Utah Model [11 Richardson EA, Seeley SD, Walker DR. A model for estimating the completion of rest for "Redhaven" and "Elberta" peach trees. HortScience. 1974;9(4):331-2.], Modified Utah Model [22 Ebert A, Petri JL, Bender RJ, Braga HJ. First experiences with chill-unit models in Southern Brazil. Acta Hortic. 1986 May;184:79-86.], and Blueberry Model [33 Spiers JM. Chilling regimens affect bud break in 'Tifblue' rabbiteye blueberry. J Am Soc Hortic Sci. 1976;101(1):88-90.]. In conclusion, the four cultivars showed a similar pattern, revealing a dormant state in the initial sampling dates and a released dormancy in the final treatments, showing the decrease of dormancy in June and July. However, Delite was earlier than the other cultivars. Bluegem and Delite required 134.0 chilling hours, 127.0 chill units (Utah Model), 198.5 chill units (Modified Utah Model), and 971.5 chill units (Blueberry Model) for 50% of their green tip buds reach the opened bud stage. Climax required 44.0, -11.0, 56.5, and 440.5, respectively. And Powderblue required 44.0, 5.5, 77.0, and 725.0 respectively. This study can bring some insights into crop management and production of this important fruit crop, especially in a global climate-changing scenario, related to flowering and dormancy control, as well as helping to select suitable cultivars to a region, concerning chilling requirements.

blueberry; bud; budbreak; chilling; climate change; dormancy; Ericaceae; Vaccinium


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