Abstract

"Boron (B) is an essential micronutrient required for physiological and biochemical processes in fruit crops such as highbush blueberry (Vaccinium corymbosum L.), well adapted species to acidic soils (pHwater ≤ 5.5) with relatively low B availability. However, an optimal range of B supplies is quite narrow, particularly among cultivars, making it easy to under- or over-fertilize which could lead to boron toxicity. Under controlled conditions, cultivars Brigitta and Legacy were grown in a peat moss substrate(pH 4.5) with five B concentrations (0, 50, 200, 400 and 800 µM). Plant biomass, nutrient concentration, water potential (Ψleaf), oxidative stress and antioxidant activity were determined at 30 d. Concentrations of 400 and 800 µM B reduced shoot and root growth in both cultivars, and800 µM B decreased Ψleaf in Legacy and significantly increased it in Brigitta. Boron applied at 400 µM resulted in the highest B accumulation in leaves of Brigitta (5-fold) and Legacy (2-fold), whereas Brigitta roots showed up to 60% increased B accumulation in comparison with 50 µM B, respectively. High B caused more severe oxidative stress in leaves of Legacy than B deficiency. The antioxidant activity was increased from 50 to 400 µM B in both cultivars. Boron added at 400 and 800 µM impaired physiological and biochemical performance probably due to toxicity, demonstrating that highbush blueberry in a genotype-dependent manner has relatively low B requirement."