Photosynthetic Limitation as a Factor Influencing Yield in Highbush Blueberries (<i>Vaccinium Corymbosum</i>) Grown in a Northern European Environment

Published evidence indicates that nearly 60% of blueberry-producing countries experience yield instability. Yield is a complex trait determined by genetic and environmental factors. Here, using physiological and biochemical approaches, we tested the hypothesis that yield instability results from year-to-year environmental variation that limits carbon assimilation, storage and partitioning. The data indicate that fruit development depends primarily on the daily production of non-structural carbohydrates by leaves, and there is no accumulation of a starch buffer to allow continuous ripening under conditions limiting for photosynthesis. Photosynthesis was saturated at moderate light irradiance and this was mainly due to stomatal and biochemical limitations. In a dynamic light environment, photosynthesis was further limited by slow stomatal response to increasing light. Finally, labelling with 13 CO 2 at specific stages of fruit development revealed a relatively even distribution of newly assimilated carbon between stems, roots and fruits, suggesting that the fruit is not a strong sink. We conclude that a significant component of yield variability results from limitations in photosynthetic efficiency that are compounded by an inability to accumulate starch reserves in blueberry storage tissues in a typical northern European environment. This work informs techniques for improving agronomic management and indicates key traits required for yield stability in such environments.</p

Treatment with fungicides influences phytochemical quality of blackcurrant juice

The impact of fungicide treatment on fungal infection and blackcurrant juice quality was examined in a series of field experiments over the course of 2 years. Fungicide treatment reduced the incidence of foliar disease and resulted in changes in the concentration of sugars, organic acids, polyphenols and anthocyanins in blackcurrant juice. Treatment with Signum® (containing pyraclostrobin, a strobilurin, and boscalid, a succinate dehydrogenase inhibitor) enhanced glucose, fructose and total sugar content in one treatment year but not in another. Treatment with Signum or Filan® (containing boscalid only) caused a reduction in the key organic acid citrate. Treatment with Signum or Platoon® (containing pyraclostrobin only) enhanced total polyphenol and anthocyanin content of juices. The data suggest a beneficial impact of fungicide treatment not only on disease control but also on juice phytochemistry