Pathotypes of Melampsora rust on Salix in short-rotation forestry plantations

Abstract

Melampsora epitea, the causal agent of leaf rust on willow (Salix spp.) in short-rotation forestry, was sampled over four consecutive years (1993-96) in Sweden. The pathotype patterns of 332 single-spore isolates were examined for virulence characteristics using a defined set of willow hosts. Thirty-seven pathotypes of M. epitea were identified and grouped into three formae speciales. No race or morph subdivision was observed among the isolates, other than the three formae speciales. For monitoring and studying the ecological and evolutionary dynamics of virulence for M. epitea, an internationally useful naming system for pathotypes is proposed, with a three-digit code referring to virulence on a specified set of standard test clones.