Managing greenhouse grown peppers in a saline environment

Abstract

Under certain conditions, greenhouse-grown pepper plants from various areas of the world, including the Mediterranean and North America, exhibit symptoms where the base of the main stem becomes swollen below the cotyledonary node level and crack-like wounds develop at the base of the stem's epidermis. Plants with this disorder develop a localized rot which can result in sudden plant wilts. This phenomenon has been observed in both, soil and soilless cultivated plants. We proposed that deposits of salts on basal stem epidermal tissues may contribute to localized injuries, which can predispose the plant to an infection by opportunistic pathogens. In greenhouse studies with peppers grown in soilless culture, the percentage of plants with epidermal wounds at the base of the stem was highest on plants where seedling containers were placed on top of the media (perlite, pine bark, or peat mix) surface of 12-L pots as compared with plants where the root ball was transplanted directly into the media. A low percentage of plants transplanted with the root ball to the cotyledonary node level exhibited epidermal damage, while plants transplanted to the second leaf node did not exhibit epidermal damage. The amount of salts deposited on the base of the stem was quantified and associated with the level of epidermal damage. A positive linear relationship occurred between the percentage of plants with epidermal wounds and the electrical conductivity of a solution obtained from washing the epidermal tissues at the base of the stem. High volumes of nutrient solution delivered close to the basal stem increased the amount of deposited salts. Simple management practices, such as transplanting deep, using cultivars with lower susceptibility to salt damage, and gradually moving back the emitter from the base of the plant after transplanting (to reduce humid conditions near the base of the stem) would help reduce the basal stem disorder in soillessgrown peppers.