The effect of root restriction on the incidence of blossom-end rot in bellpepper (Capsicum annuum L.)

Water and calcium uptake are important factors affecting the incidence of f ruit blossom-end rot (BER) in tomato and pepper. In the present study an at tempt was made to manipulate these factors by severe root pruning and to ex amine the effect on BER in greenhouse-grown bell pepper (Capsicum annuum L. , cv. Mazurka). Pepper plants were transplanted, with the root system split into four separated compartments, each containing a single root quarter. R emoval of half, or three quarters, of the root from fruit-bearing plants si gnificantly reduced fruit EER incidence compared with plants with intact ro ots, especially in fruits which were at the rapid expansion stage at the be ginning of the treatments. Removal of three quarters of the root reduced mi dday leaf water potential, stomatal conductance, and plant height. The numb er and weight of fruits were not affected by these treatments. Root pruning caused only a slight reduction in stem sap flow, as measured by the heat p ulse technique. Calcium concentrations in the distal part of fruits from qu arter-root-plants were higher than in fruits from non-pruned plants, wherea s magnesium and potassium concentrations were not affected. On the other ha nd, in the leaves, calcium, magnesium and potassium concentrations were all reduced by root pruning. The K/Ca ratio decreased in the blossom-end of th e fruits and increased in the leaves of root-pruned compared with control p lants. The results suggest that root pruning did not affect the total uptak e of calcium, apparently driven by transpiration, but did enhance calcium p artitioning to the developing fruit. Root pruning also affected calcium dis tribution within the fruit and therefore attenuated EER incidence.