Variability in Pathogenicity of Poplars Rusts (Melampsora spp.) and Selection of Clones for Durable Resistance

1993

S. 185-186

Unselbständiges Werk

200077382

Poplar is a fast-growing tree under temperate climate. Easy vegetative propagation and cultivation of only a limited number of clones favor several diseases. Leaf fusts affect poplar growth. Recently, several clones lost their resistance to M. larici-populina. Physiological races of the pathogen are involved. They can be distinguished with a set of four clones (or groups of clones). We suggest that, at least, 16 races potentially exist, half of them having been found in France. After crossing two races, we concluded that virulence is likely to be recessive and that isolates are often heterozygous. Increasing cultivation of clones with race-specific resistance leads to a rapid increase of inflection on such clones and consequently to a higher frequency of virulent races on poplar and larch (the alternate host). Artificial inoculation of various clones in the laboratory indicates that some have a durable resistance. While infected by all known races, they exhibit a long latent period and few flecks.