Characterization of Tunisian castor bean genotypes using SDS-PAGE of total seed storage proteins

Due to the chemical and physical properties of castor oil (Ricinus communis L.) that make it a valuable raw material for numerous industrial applications, including the production of biofuel, interest to develop more and better varieties has been increased. The objectives of this work, were to find out the level of genetic variability present in 56 Tunisian castor germplasm by using the electrophoretic profiles of total seed proteins with different molecular weights through SDS-PAGE. Fifty-six castor (Ricinus communis L.) genotypes were used in the present study. Seeds of castor were obtained from the University of Carthage, National Institute of Research in Rural Engineering, Waters and Forests (INRGREF), Regional Station of Gabès, Tunisia. Storage proteins were extracted from individual grains by the standard reference electrophoretic method by ISTA in the presence of sodium dodecyl sulfate (SDS-PAGE). The number of total scorable protein bands was twentynine as a result of SDS-PAGE technique but those that were not cosistent in reproducibility and showed occasional variation in sharpness and density were not considered. Out of twentynine polypeptide bands, 5 (18%) were commonly present in all accessions and considered as monomorphic, while 24 (82%) showed variations and considered as polymorphic. The size of the protein bands obtained through SDS-PAGE ranged from 30 to 180 kDa. On the basis of banding profiles of proteins of different kDa, gel was divided into zones A, B and C. The major protein bands were lied in zones A and B, while minor bands were present in zones C. The dendrogram tree demonstrated the relationship among the 56 Tunisian castor genotypes according to the similarity index, using UPGMA cluster analysis. The dendrogram was divided into three main clusters. Similarly the present study of genetic variability in the seed storage polypeptide determined by SDS-PAGE technique proved that it is fruitful to identify genetic diversity among accessions of castor.