Variation in leaf phenolics of field-cultivated willow (Salix myrsinifolia) clones in relation to occurrence of Melampsora rust

Concentrations of potential antifungal phenolics in field-cultivated willow (Salix myrsinifolia) clones were analysed during three growing seasons, and correlated to the occurrence of Melampsora rust. Consistent relationships between phenolics and rust were nor found across the experimental years. There was significant clonal and temporal variation in phenolic content and rust frequency. Levels of some phenolics varied considerably within a sequence of four full-grown leaves, bur the variation in rust occurrence within the same leaf sequence was nonsignificant. The results suggest that the possible association between willow phenolics and rusts is not straightforward, and emphasize the importance of long-term studies to investigate the chemical basis of willow-rust interactions.