Distinction between stem- and leaf-infecting forms of Melampsora rust on Salix viminalis using RAPD markers

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.