[1] James Hutton Inst, Cell & Mol Sci, Dundee DD2 5DA, Scotland
[2] James Hutton Ltd, Dundee, Scotland
[3] Int Potato Ctr, Lilongwe, Malawi
[4] Bvumbwe Agr Res Stn, Dept Agr Res Serv, Limbe, Malawi
[5] Masinde Muliro Univ Sci & Technol, Dept Agr & Land Use Management, Kakamega, Kenya
[6] Univ St Andrews, Sch Biol, Biomol Sci Bldg, St Andrews, Fife, Scotland