| Abstract: | Among pests and diseases occurring in coppiced willow plantations established to produce biofuel, Melampsora rust is the most widespread and severe. In the present study, the variation in rust attacks in a set of Salix viminalis clones was investigated. The aim was to look for trends possibly arising from changes in rust genotype composition, to get some idea about the risks of rust overcoming resistance bred into new willow varieties. Rust levels on 92 S. viminalis clones belonging to 18 different families were scored once each year during 1987–96 in a plantation in southern Sweden. Rust scorings in 1993 deviated most from the average scoring pattern of the clones. Furthermore there was a successive change, such that the longer the time interval between scorings the lower was the correlation between rust scores. Willow families were identified that deviated from the others over time. Various explanations for inconsistency in rust scores over time are discussed. |
