DISTINCTION BETWEEN STEM-INFECTING AND LEAF-INFECTING FORMS OF MELAMPSORA RUST ON SALIX-VIMINALIS USING RAPD MARKERS

The RAPD technique was used to distinguish two forms of Melampsora rus t 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 b ands specific for the stem-infecting form and four primers produced fi ve bands characteristic of the leaf-infecting form. Cluster analysis u sing 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 lea f-infecting isolates showed up to 29% variation.