Components of resistance of leaf rust (Melamspora laricii epitea Kleb./Melampsora ribesii-viminalis Kleb.) in Salix viminalis L.

Selection on partial resistance components, namely latent period, development rate of uredia and number and size of uredia, has been suggested as a means to achieve durable resistance. Three experiments were carried out in growth chambers to assess the impact of environmental and genetic factors on these components in the Salix-Melampsora host-pathogen system. They confirmed the environmental ability of the Melampsora-Salicaceae relationship and provided no definite answer on the possibility of attaining durable resistance through selection on partial resistance components. On the one hand, there is a large amount of heritable variation among clones for most components; on the other hand, all components were extremely sensitive to environmental conditions and isolates, making the development of standard selection methods difficult.