The RAPD technique was used to distinguish two forms of
Melampsora rust on Salix viminalis. Fifteen
isolates of the stem-infecting form and 19 of the leaf-infecting form
collected from the U.K. were tested with 10 arbitrary primers. All
the primers generated polymorphic bands and 46 putative loci were
examined. Seven primers gave a total of eight bands specific for the
stem-infecting form and four primers produced five bands
characteristic of the leaf-infecting form. Cluster analysis using
Unweighted Pair-Group Method with Averaging (UPGMA) revealed 62%
disagreement between the two forms. The RAPD band patterns of the
stem-infecting form isolates were almost identical, while those of
the leaf-infecting isolates showed up to 29% variation.