Genetic diversity of seed storage protein in the Ethiopian garden cress (Lepidium sativum L.)

The Ethiopian garden cress (Lepidium sativum L.) is an important crop extensively used as food and medicine. In this study, total seed storage proteins of 112 garden cress genotypes collected from diverse growing regions in Ethiopia were investigated to assess patterns of genetic diversity and relationships. Using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), a total of 1774 stable protein bands were identified through discontinuous electrophoresis. Of these, 1597 bands were polymorphic. A maximum of 20 protein sub-units in the range of 15 to 75 kDa were observed per genotype. The similarity coefficient among these genotypes ranged from 0.25 to 1.00 with an average genetic dissimilarity of 0.2754. On the basis of Ward Euclidian distance, the genotypes were grouped into five major clusters, the largest one comprised of 62 genotypes (Cluster III) followed by 26 genotypes in Cluster I. Cluster IV and V contained a total of 14 genotypes that were the most distantly related to other groups, and thus can be potentially used as parents for exploitation of heterotic effects in hybrid breeding programs. Our findings using SDS-PAGE profiles revealed no obvious association between geographic region of origin and germplasm clustering. However, the polymorphism and cluster analysis indicated that garden cress genotypes differed greatly in the composition of seed proteins. This shows that protein profiling could be used as a rapid and reliable method for genetic diversity studies. In order to fully explore the protein based genetic diversity in garden cress germplasm, techniques such as 2-D gel electrophoresis are recommended in future studies.