Comparing Chilean and Swedish rust populations: possible impact of long‐distance transport of Melampsora rust

Abstract

Summary As willow (Salix) cultivation grows globally, worldwide monitoring of pathotypes for Melampsora rust, the most serious disease in willow, becomes increasingly important. We compared the pathotype composition of the Melampsora rust population in Chile with that in Sweden and assessed inocula exchange for the rust between the continents. For pathotyping rust isolates, a willow differential was used (a standardized set of willow test clones) to obtain clone‐virulence patterns. These patterns were used to identify virulence components involved in determining which willow clones a given individual pathogen isolate (genotype) can successfully attack. Each virulence component detected earlier in Sweden's rust population was present in Chile's rust population. Using isoenzyme analysis to classify willow species in Chile, a low genetic variation of Salix viminalis (an introduced willow species) was found, compared with the endemic species Salix humboldtiana. Comparison of rust populations for the two countries supports the present hypothesis that intercontinental inocula exchange can be a significant determinant of local pathotype structure, and consequently can be important for willow‐resistance breeding.

Abundance of willow rust (Melampsora sp.) on different willow clones in Estonian energy forest plantations

“…The most widespread and frequent disease in willow plantations is leaf rust, caused by Melampsora spp. Mostly Melampsora larici-epitea, with many pathotypes, parasitizing on different willow clones, is found to cause the greatest damage in energy forest plantations (Pei et al, 1993(Pei et al, , 2002Ramstedt, 1999;Hurtado & Ramstedt, 2003). This is a leaf infecting form that requires larch (Larix sp.…”