Blueberry ripening mechanism: a systematic review of physiological and molecular evidence

Blueberry (Vaccinium spp. section Cyanococcus) ripening is a complex process involving physiological and molecular changes that affect harvest timing, fruit quality, and market value. This review examines scientific literature on blueberry ripening, aiming to establish a unified phenological framework for lowbush (Vaccinium angustifolium), highbush (Vaccinium corymbosum, including northern and southern types), and rabbiteye (Vaccinium virgatum Ait; syn. Vaccinium ashei Reade) blueberries. Blueberries follow a double-sigmoid growth pattern, with epidermis color changes marking the onset of ripening. Traditionally, fruits are classified as climacteric or nonclimacteric based on respiration rates and ethylene production. However, blueberry genotypes exhibit significant variability in these traits. Some genotypes exhibit high respiration rates during fruit color transition, but ethylene production maxima vary or may be absent. The diversity among blueberry genotypes and differences in research methodologies contribute to inconsistencies in reported data. Thus, a unified classification of blueberry ripening remains premature. Nevertheless, agronomic practices and ripening-related gene networks are available to enable future studies. This review also explores the implications of these findings for farmers and consumers.