Effects of different potassium nitrate concentrations and temperature conditions on the elemental composition and blossom-end rot in paprika (Capsicum annuum l.)

Abstract

Blossom-end rot (BER) in paprika (Capsicum annuum L.), as in tomato fruits, is a physiological disorder caused by calcium (Ca) deficiency in fruits. While studies have revealed that excessive nitrogen and potassium fertilization and high temperatures affect Ca transport to fruits and induce BER, few studies have investigated the effects of other elemental concentrations in paprika fruit and their association with BER occurrence. This study aimed to investigate the relationship between the changes in the elemental composition and incidence of BER in paprika fruits grown at different potassium nitrate (KNO3) concentrations and different temperature conditions. Paprika plants were grown in rockwool blocks in a greenhouse at 25°C and 30°C for approximately four months and irrigated with liquid fertilizer and three different concentrations (0, 27.9, and 74.4 mM) of KNO3 were added. Subsequently, the total fresh weights of ripe paprika fruits and the incidence of BER were measured, and the elemental compositions in the pericarp of the first and last sampled fruits were analyzed. The total fresh weights significantly decreased and the incidence of BER increased with increasing KNO3 concentrations and temperature. The profiles of 11 mineral elements in the pericarps of paprika fruits revealed a significant positive or negative correlation between not only the concentration of Ca, but also that of several other elements including boron (which crosslinks pectin in the cell wall like Ca) and the incidence of BER. These results suggest that Ca deficiency may not be the only cause of BER occurrence, and that several elements may also be involved. The insights from this study will contribute to help predict the incidence of BER and stabilize crop production by improving fertilizer application and environmental control.