Masaaki Hohjo

Hydroponic Production of Low-Potassium Tomato Fruit for Dialysis Patients

ABSTRACT Chronic kidney failure is becoming a global problem. Patients with kidney failure cannot excrete excess K, and their intake of K is often restricted. If low-potassium (K) tomato fruit can be produced, it can improve the dietary options of dialysis patients and their quality of life. A method of producing low-potassium (K) content tomato (Solanum lycopersicum L.) fruit was investigated. Several medium-sized tomato cultivars were tested, and the K supply was restricted using hydroponic production. Some plants were maintained through setting of a single fruit truss, and fruit fresh weight was not affected by K restriction. Total K uptake per plant decreased by 92% with lower K compared to conventional cultivation in which K content in fruit decreased by only 25%. Other plants were maintained until three trusses per plant were set, and fruit K content decreased 40% to 60% depending on cultivar because of K restriction. The cv. Aichan was the most sensitive and cv. Frutica was the least sensitive to K restriction. Total soluble solids content decreased slightly. Titratable acid content was affected by K restriction and decreased 20% to 40% depending on cultivar. In either case, K withdrawn in hydroponic culture following anthesis of the third truss was effective in producing low-K tomato fruit and could decrease fruit K content to at least 50% of expected tomato fruit K content.