Pruning severity affects yield, fruit load and fruit and leaf traits of 'Brigitta' blueberry

Abstract

Pruning is crucial to balance productivity and fruit quality in blueberry orchards. Slight, conventional and severe pruning treatments were applied on 4- and 5-year old bluberry plants cultivar 'Brigitta' to evaluate their effect on yield, leaf area, gas exchange and fruit load as driver of fruit quality traits. Yield and berries per plant decreased with increasing pruning severity, whereas canopy leaf area increased. The resulting fruit load ranged from 0.2 to 1.4 fruit per cm2 leaf area. Fruit weight, dry matter, glucose and fructose were negatively related to fruit load, with fruit fresh weight decreasing to greater extent than sugars. Berry weight was restricted by source limitation during the initial cell division and initial cell enlargement fruit growth phases as indicated by decreased relative growth rate. Light-saturated photosynthetic rate diminished with increasing pruning severity indicating a sink limitation of photosynthesis. The strong association between photosynthesis and stomatal conductance shows a high corregulation in the response of carbon and water exchange to sink demand. Our results underline agronomic and physiological factors determining blueberry yield and fruit quality and can be useful for agro-technical management.