No abstract

Cowpea (Vigna unguiculata) is used in West Africa for both human consumption and animal feeding. Despite its importance, the production of the crop is hampered by biotic and abiotic constraints. To overcome these constraints, the Senegalese Institute of Agricultural Research (ISRA) has set up a breeding program since 1960 leading to the release of productive varieties. Information of the genetic diversity for these varieties could improve the effectiveness of further breeding programs. The objectives of this study was to assess the genetic diversity and the population structure of 11 cowpea improved varieties from ISRA collection. Twelve (12) polymorphic microsatellite markers were used and the analysis of genotypic data showed a total of 39 alleles ranging from 2 (SSR6288, SSR6311 and SSR6827) to 6 (SSR6807) per locus. Polymorphism rate ranged from 8.33% (Mougne and Kelle) to 58.33% (Mouride) with an average of 31.06%. Intra varietal genetic diversity was very weak (0.012 to 0.091). The genetic similarity revealed that Melakh and Pakau varieties were genetically the closest while Bambey 21 and Sam were the most distant. These results are confirmed by the dendrogram, which also showed that Thieye, Leona, Kelle, Sam, Mougne and Yacine varieties have a higher genetic stability than Lisard, Melakh, Pakau, Mouride and Bambey 21. Eighty-seven percent (87%) of the total variability was attributed to inter varietal variability while 17% was due to intra varietal variation. These results provide a better knowledge of genetic resources of cowpea varieties released and held by ISRA and constitute important input for further cowpea breeding programs.

To test the tolerance of cowpea mutants to salinity, cowpea wilds and mutants were subjected to 50, 100, 150, 200, and 250 mM NaCl to test for tolerance to salinity. Genotype and salt concentration interaction were significant. GxS explained mostly the variation observed. More informative salt concentrations were found in 50 mM (99.08) and C100 mM (72.50) against 26.80 in the control environment. High salt concentrations had the lowest germination rates. Seed germination rate of cowpea genotypes decreased from 56.46 to 20.58 with a mean of 36.28 and a variance of 99.08. Despite strong correlations observed between indices, very weak ones were found between AD and STI, -0.02, -0.44, -0.7, -0.79 and -0.84 respectively at salt concentration of 50, 100, 150, 200 and 250. Mouride wild types were most tolerant to salt with a germination rate of 43 % at 50 mM versus 48 and 551 % for respectively Melakh and Yacine. Six (6) mutants were more tolerant to the weakest checks performance which was the 9th best performance.