POLYMORPHISM OF PEPPER (CAPSICUM-ANNUUM-L) SEED PROTEINS STUDIED BY 2-DIMENSIONAL ELECTROPHORESIS WITH IMMOBILIZED PH GRADIENTS - METHODICAL AND GENETIC-ASPECTS

A population of ten morphologically similar inbred lines of pepper (Ca psicum annuum L.) has been investigated for polymorphism of seed prote ins by two-dimensional (2-D) electrophoresis with immobilized pH gradi ents. To reveal as much variation as possible, both the water- and the urea/detergent-soluble protein fraction were electrophoretically anal yzed and subsequently visualized by silver staining. The 2-D patterns were subjected to computer analysis to be able to establish genetic va riation. A high number of the seed proteins were found to be variable as to presence/absence: these were 68 out of 184 reproducible water-so luble proteins and 34 out of 419 reproducible urea/detergent-soluble p roteins. Comparison of the 2-D data of the water-soluble and the urea/ detergent-soluble proteins, which represent the biggest part of all ex tractable seed proteins, showed that both protein fractions have prote ins in common, but the variable proteins found in both fractions were non-identical. The difference of variability scored in both solubility fractions was discussed. Genetic distances between all pairs of inbre d pepper lines were calculated and a genetic tree was constructed. A c orrelation analysis was carried out to correct for genetic linkage and for secondary modifications, to have a more proper estimate of geneti c distances. In both cases the dendrograms showed two distinct genetic groups of five inbred lines. This electrophoretic study was done in o rder to utilize the genetic distance data in breeding for heterosis. T he genetic distance data presented will be used to validate the assump tion that there is a higher chance to achieve better hybrid performanc e when the genetic distance between the parents is as great as possibl e. From the fact that we found a high level of genetic variability wit hin a population of ten morphologically similar inbred lines, it can b e concluded that 2-D electrophoresis can be efficiently applied in pep per breeding.