Analysis of correlation coefficients is an important tool, not only in the study of the association between the characteristics of the cowpea but also in evaluating the contribution of each factor to the productivity of the crop. The objective was to investigate the genotypic relationships between grain productivity in the cowpea and various production components and agronomical characteristics, by using path analysis to break down such correlations in both their direct and indirect effects. The experiment was carried out from May to August of 2010. The cultivars used were BR8 Cauldron, IPEAN V69, BRS Guariba and BR17 Gurguéia. Genotypical correlations between pairs of characteristics, together with their direct and indirect effects were estimated, taking into consideration production components (number of pods per plant and number of seeds per pod), agronomic features (plant height, leaf-area and shoot dry-matter weight) and grain productivity. A path diagram containing two path-chains was sufficient to explain the relationships between the primary and secondary components and productivity when the high estimates of the coefficients of determination (R²) and the low residual effects were considered. The number of pods per plant, and leaf-area were those characteristics which most correlated with productivity, and would appear to be efficient for indirect selection, where the intention is to obtain genetic gains in grain yield. They were also seen to be important characteristics for the indirect effects of the number of seeds per pod, plant height and shoot dry-matter weight.
Cowpea; Genotype-environment interaction
