[1] Egerton Univ, Dept Crops Hort & Soils, Njoro 20115, Kenya
[2] Egerton Univ, Dept Biochem & Mol Biol, Njoro 20115, Kenya
[3] KALRO, HRI, Tigoni 338, Limuru, Kenya
[4] Univ Republica, Fac Agron, Montevideo, Uruguay
[5] Univ Fed Vicosa, Dept Agron, BR-36570900 Vicosa, MG, Brazil
[6] Int Potato Ctr, Nairobi 00603, Kenya