Relationship between the occurrence of bitter fruit in cucumber (Cucumis sativus L.) and the contents of total nitrogen, amino acid nitrogen, protein and HMG-CoA reductase activity

In order to describe the mechanism of the occurrence of bitter fruit in cucumbers (Cucumis sativus L. cv. Kagafutokyuri) and encourage more profitable effects by growers, an investigation of the development of the bitter principle, cucurbitacin C, was conducted. The occurrence of bitter fruit was higher in plants grown in lower air temperatures, in plants of the bitter lines and in plants cultivated with twice as much nitrogenous fertilizers as usual, than in plants grown in higher air temperatures, in plants of the nonbitter lines and in plants cultivated with the usual amount of nitrogenous fertilizers. Total nitrogen, amino acid nitrogen, and protein contents and HMG-CoA reductase activity were higher in leaves of plants that produced higher occurrence of bitter fruit, and were higher in the bitter fruit than in the non-bitter fruit. (C) 2003 Elsevier Science B.V. All rights reserved.