Seasonal Patterns of Soluble Carbohydrates in Spring- and Fall-Blooming Southern Highbush Blueberry Genotypes

Temperature and daylength are key factors associated with soluble carbohydrates (SCs) partitioning in plant organs. Environmental cues and SC concentrations influence flower bud initiation (FBI) in fruit crops. Southern highbush blueberry (SHB, Vaccinium corymbosum interspecific hybrids) is a daylength-responsive crop. In most SHB genotypes, decreasing photoperiod and temperatures in the fall season trigger FBI, followed by bloom in the spring. Blueberry genotypes that bloom during the fall season have been identified in the University of Florida’s SHB breeding germplasm. Off-season bloom suggests that FBI in those genotypes occurs under atypical environmental conditions. Drawing from these findings, we hypothesized that SC concentrations in fall-blooming genotypes differ from spring-blooming genotypes, especially in the period that precedes bloom. In this study, we quantified and compared SC concentrations of SHB genotypes with off-season and traditional spring-blooming phenology across 2 years. In addition, we recorded the developmental stages of each genotype at the SC sampling points. Our results indicate that SHB plants exhibit high SC concentrations during the winter before the traditional spring bloom, which agrees with prior studies in temperate fruit crops. However, no increase in SC concentrations was detected before fall bloom, indicating that this trait might be regulated by other endogenous factors. Further research on carbohydrate partitioning, metabolic pathways, and agricultural practices could support the investigation of off-season blooming in blueberry, contributing to the breeding of varieties with off-season production and the expansion of blueberry growing regions.