Source–Sink Relations in Non-dormant and Dormant Blueberry Production Systems

Abstract

Two cultivars of southern highbush blueberry (Vaccinium corymbosum interspecific hybrid) were grown in containers under the traditional dormant production system or the non-dormant production system. Plants in the non-dormant production system were maintained by continuous N fertilization throughout the year. The first objective was to determine when source limitations to reproductive development in blueberry occurred. The second objective was to determine if source limitations could be alleviated by the non-dormant production system, since photosynthesis and therefore carbohydrate accumulation continue later into the season. In order to determine when source limitations occurred, reproductive manipulations were applied to three groups of plants, either after flower bud differentiation in the fall, or after fruit set in the spring. After flower bud differentiation, 80% of the flower buds were removed from one plant group. After fruit set, 80% of individual fruits or 80% of fruit clusters were removed from two other plant groups. Average fruit dry weight was higher in the flower bud removal treatment than in the fruit removal or control treatments in the dormant production system, indicating a source limitation occurs prior to anthesis. No pre-anthesis source limitation was found in the non-dormant system; this is probably due to insufficient fruit and flower removal, and/or continued flower bud initiation prior to anthesis in this system. However, both fruit number and total yield were significantly higher in the non-dormant than the dormant production system.