Multilocational Evaluation of White Yam Genotypes Using Gge Bi-Plot Methodology

Yams are cultivated in diverse agroecologies and there is evidence of strong genotype and environment interaction. This has necessitated the evaluation of new yam genotypes in multi-locational trials. Five new white yam genotypes were evaluated in different locations of major yam  producing areas; Umudike, Nsukka, Ubiaja, Abuja and Katsina-Ala, to test the performance and stability of these genotypes across the environments using GGE bi-plot software. The GGE bi-plot generated several graphic  bi-plots which showed Umudike, Nsukka, Ubiaja and Katsina-Ala as  belonging to one mega – environment while Abuja and Ubiaja belong to another. The GGE bi-plot also showed the discriminating and  non-discriminating environments. Katsina-Ala was the most discriminating environment while Nsukka was the least. A test environment that lacks discriminating ability lacks the capacity to provide information about the genotype being used. Such environment lacks usefulness and should be discarded as a test environment. Katsina-Ala, with the longest vector is the most discriminating. This is followed by Ubiaja, Umudike and Abuja in that order. Nsukka is the least discriminating. KEYWORDS : Yams, multi-environment trial. GGE biplot,  mega-enviroments.