Understanding Yield of Cranberry: Bud Development, Carbohydrate Allocation, and Yield Component Analysis

Cranberry (Vaccinium macrocarpon Ait.) is a high-value fruit crop native to northeastern continental America. Yield of cranberry is a complex trait influenced by multiple genetic, physiological, and environmental factors. The research addressed in this dissertation expanded upon the current knowledge of yield through a holistic approach that ranged from basic scientific investigations of cranberry physiology to applied research that involved modeling crop yield. Evaluations of terminal bud development and the potential for return bloom found cultivars generally initiate flowers by mid-to-late July and initiation is not associated with a specific value of growing degree day accumulation. These results suggest photoperiod may be involved in floral initiation. Terminal buds were also wider among recent cultivar releases and had an increased potential for return bloom. Comparisons of nonstructural carbohydrates across cultivars that differ in biennial bearing tendencies and return bloom demonstrated concentrations are lowest during flowering and fruit development, which coincides with terminal bud development. Concentrations remained low in 'GH1', which has greater biennial bearing tendencies relative to other cultivars included in the study. These findings suggest carbohydrate limitations at the time of fruit set through berry and terminal bud development may inhibit the formation of mixed buds and contribute to biennial bearing. The final project evaluated genetic, physiological, and environmental components of yield and assessed the practicality of developing improved methods of yield prediction for early crop forecasting purposes. Berry number was found to explain most of the variability associated with yield, which is not conducive for early crop forecasting given these variables are determined later in the season. Difficulties associated with developing an improved method of yield prediction are due to the biological complexity of cranberry and the diversity of implemented management practices that are not readily quantifiable for modeling purposes. Results from this project demonstrate the temporal and spatial variability of cranberry yield and associated challenges with yield prediction. Future research should seek to develop an improved understanding of the sources and specific implications of this observed variability. Management and minimization of variability could promote elements of sustainability within commercial cranberry production.