The objective of this work was to evaluate the grain yield stability and adaptability of 15 cowpea (Vigna unguiculata) genotypes using the additive main effects and multiplicative interaction model. The trials were carried out at 13 environments of Piaui and Maranhão, Brazil, from 1999 to 2001. Genotype showed low effect, but environment, genotype x environment interaction, and the first tree axes of the principal components analysis were highly significant (P<0.01). The principal components analysis explained 72.82% of the sum of squares of the genotype x environment interaction. Evx 91-2E and Evx 63-4E genotypes showed high adaptability and stability and can be cultivated in all environments. Evx 47-6E and Evx 92-49E genotypes were adapted to low yield environments, while Evx 63 - 10E genotype had the highest yield averages, and specific adaptation to high quality environments. Brejo, MA, 2001, and Bom Jesus, PI, 2000 environments were the most previsional ones, while Teresina, PI, 2001, and Baixa Grande do Ribeiro, PI, 2001, were higly unstables. The genotype x environment interaction is variable inside and homogeneous between the states of Piauí and Maranhão in terms of environmental quality.
Vigna unguiculata; rope bean; macassar bean; genotype x environment interaction; phenotypic response
