Enzyme and storage protein electrophoresis in varietal identification of sugar beet.

Different methods of classification, based on total protein patterns as well as on specific isoenzyme patterns, were compared in order to establish an identification system for sugar beet varieties and lines. Single seed patterns and bulk extractions of total and fractionated proteins were compared on SDS-PAGE. Due to important intra-populational variation contrasting with similarity at the varietal level no method proved to be sufficiently discriminatory. Twelve sugar beet lines have been genotypically fingerprinted on the basis of five allozyme systems. The allele frequencies of each variety have been measured by using 60-100 individuals. From the data, genetic distance coefficients have been calculated in order to group the different entries by cluster analysis. In addition, a comparison has been made between two seed lots independently obtained from the same parental lines, to test the stability over years. Seeds from the same parental lines, but produced in different localities (Denmark, Italia and USA), were compared to test the influence of the environment on the classification. It has been concluded that isozymes could provide a useful tool for cultivar distinction. The variability at the level of allele frequencies within localities was small. The stability of different generations of the strains was relatively constant. Different strains originating from the same seed firm were less distinct than strains originating from different seed firms.