Genetic and morphological diversity of cowpea (Vigna unguiculata (L.) Walp.) entries from East Africa

Cowpea (Vigna unguiculata (L.) Walp.) is widely grown by subsistence farmers in West and East Africa where its grain and leaves are sources of highly valuable food, due to their high contents of proteins, minerals and vitamins. Therefore, cowpea could play a significant role in mitigating malnutrition such as micronutrient deficiencies. The objectives of this study were to evaluate the performance in agronomic traits of cowpea entries (released and farmers' cultivars, and gene bank accessions) from different sources, and to assess the extent of genetic diversity in this material to provide basic information for its use in breeding programs. A total of 15 entries were evaluated. All entries were morphologically uniform, except the farmers' local cultivars. Fresh leaf yield varied from 34.6 to 52.8 g per plant and days to 50% flowering from 64 to 82 days. Hundred seed weight ranged from 7.67 to 15.12 g. On average, the number of pods ranged from 4.8 to 15.6 pods per plant. No correlation between fresh leaf yield and other traits was detected, whereas the number of pods per plant and the hundred seed weight were negatively correlated. Genetic diversity was assessed on five genotypes per entry using 544 Amplified Fragment Length Polymorphism (AFLP) and 18 microsatellite markers. Genetic distances calculated using the Jaccard algorithm ranged from 0.002 to 0.193 among genotypes of the same entry and from 0.098 to 0.301 for genotypes from different entries. A principle coordinate analysis separated four entries from the rest. Although the consensus tree based on Neighbor Joining trees was unable to resolve the whole cluster, an assignment of most of the entries into entry-specific clades was possible.