Success of most crop improvement programs depends mainly upon the existence of the genetic variability and the heritability of desirable traits in the material under selection. Magnitude and type of genetic variability are important for determining the selection criteria and breeding schemes to be used for improvement purposes. Three related experiments were conducted at Sakha Agricultural Research Station, Agricultural Research Center during three successive summer seasons; 2013-2015 to evaluate 24 cowpea genotypes including the check variety (Balady) and to select the best ones considering the yield and yield components under the study. Data revealed that highly significant differences exist among the genotypes for most the studied traits The result, however, revealed The genotype (G12) had the highest values for total fresh (25.8 kg/plot) and dry yield (2.639 kg/plot). On the other hand, G5 showed the lowest value (10.6 k/plot) for total fresh yield. The genotype (G4) surpassed the other genotypes in both evaluated seasons; 2014 and 2015 for all the studied traits. This may indicate the possibility to carry out a selection program to improve and develop new cultivar. In addition, results showed considerable variation among the genotypes in broad sense heritability estimate (h2) in 2013 and was 60.9% and 99% for the stem diameter and fresh yield for second cut, respectively. On the other hand, the heritability estimates were 82.7% and 98.9% for number of branches and dry yield for the first cut; respectively, in 2014 and 83.1% and 99.3% for number of branches for first cut, and fresh yield for second cut; respectively, in 2015.
The genetic relationship among genotypes based on agro-morphological analysis showed significant variation among the genotypes over all the traits under the study. High similarity between (G20) and (G21) in 2013 and a close relation between (G3) and (G4) in 2014 and 2015 had achieved. Similarity level ranged from 43.98% to 96.02% in the first season (2013) and from 19.55% to 83.39% in the second season (2014) and from 21.91% to 84.17% in the third season (2015).