Optimization of correlation and path coefficient analyses as selection techniques for yield in locally grown cowpea [Vigna unguiculata (L) Walp]

This research paper was aimed at investigating the extent of relationship between yield and yield-contributing traits, which will facilitate selection of high performing genotype(s) of local cowpea. Seeds of three varieties of locally grown cowpea were sown in a randomized complete block design (RCBD) in ten replications. The field study was done at the University of Calabar Experimental Farm, University of Calabar, Nigeria, during the 2008-2009 growing season. Correlation coefficients and path coefficients were estimated on yield and yield-contributing traits. Results when averaged revealed that vein length-1 negatively correlated with the number of leaves-1 (-0.63*) and pod length-1 (-0.653*) while correlating positively with number of nodules-1 (0.605*). There was significant positive relationship between number of leaves-1 and pod length-1 (0.552*) and number of seeds-1 (0.641*) while correlating negatively with number of nodules-1 (-0.722*). Significant relationships were also observed between leaf area-1 and pod length-1 (0.587*) and number of pod-1 and 100-seed weight (0.683*). Other character had associations with one another though not significant. The genotypic correlation coefficient was partitioned into direct and indirect effects. It revealed that vein length-1 (-0.926), leaf area-1 (-0.619), pod length-1 (-0.621) and number of pods-1 (-0.116) had negative direct effects on yield while number of leaves-1 (0.788), number of flowers-1 (0.278), number of nodules-1 (0.551) and 100-seed weight (0.548) had positive direct effects on yield. However, number of leaves-1 had the highest direct effects followed by 100-seed weight, number of nodules-1 and number of flowers-1. Explicitly, our results are indications that for the selection of superior genotypes of cowpea during any breeding programme, the genotype(s) with higher number of leaves, number of nodules, number of flowers, 100-seed weight should be considered in conjunction with those with broader leaf area and long pods.