1. Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas, ES–50080 Zaragoza, Spain
2. Department of Food Science, Minami‐Kyushu University, Kirishima 5‐1‐2, Miyazaki 880‐0032, Japan
3. Department of Biology, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka 422‐8529, Japan
4. College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
5. (present address) Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK