[1] Scottish Crop Res Inst, Soil Plant Dynam Unit, Dundee DD2 5DA, Scotland
[2] Nagoya Univ, Grad Sch Bioagr Sci, Chikusa Ku, Nagoya, Aichi 4648601, Japan
[3] Univ Bristol, Long Ashton Res Stn, Dept Agr Sci, IACR Long Ashton, Bristol BS41 9AF, Avon, England