43 January.June 1994 Possible Use of RFLP in Repeated Sequence Families Possible Use of RFLP in Repeated Sequence Families in Sugar Beet Breeding and For Management of Sugar Beet Genetic Resources

Because they usually correspond to unique sequences, RFLP markers are used in genomic mapping, variety distinction, variety homogeneity and in reconstruction of phylogenies. Nevertheless, they are not the most suitable markers for all these applications. Their use in taxonomy is not always straightforward, since these sequences may be highly conserved as in the genus Beta L. The analysis of genetic variability allows calculation of genetic distances and enables the construction of phenograms, but not phylogenetic trees. Phylogenetic trees are constructed using other methods based on parsimony analysis and, hence, they do not always fit within taxonomic groups. Therefore, we have turned to other molecular markers which have already been found in sections Beta, Corollinae and Procumbentes, and, therefore, fit well into the main taxonomic divisions. RFLPs with repeated sequences are generally not used, although they offer a wide range of potential applications. Some have already been used and others appear suitable for use as markers. Here we present results with moderately and highly repeated sequences which display RFLP or are genome specific when used as probes. The main advantages and disadvantages of both RFLP types are discussed. Additional Key Words: moderately and highly repeated sequences, satellite DNA, molecular taxonomy, genetic variability, variety identification