Reduction of leaf lettuce tipburn using an indicator cultivar

•Leafy vegetables, including lettuce, undergo tipburn, a Ca-deficiency symptom.•A sensitive cultivar was tested as an indicator for the early detection of tipburn.•An indicator cultivar and Ca chaser suppressed tipburn damage to the target cultivar.

Tipburn is a physiological disorder caused by a calcium (Ca) deficiency that occurs mainly in leafy vegetables, such as lettuce, resulting in a reduced commercial value. To prevent tipburn injury, a sensitive cultivar was tested as an indicator for early symptom detection. An indicator cultivar began to develop tipburn two days earlier than the target cultivar. This allowed for the rescue of the target cultivar by the addition of extra Ca. The yield rate was improved from 4% to 70% with the use of an indicator cultivar in the hydroponic cultures. The top fresh weight of the target cultivar when using an indicator cultivar decreased compared with control plants, but increased compared with negative control plants lacking Ca in the culture. Water contents and root lengths were not affected by the use of an indicator cultivar and additional Ca. These results were consistent with other target cultivars under excess ammonium conditions. This system may be used against tipburn incidence without additional costs and equipment in plant factories.