Épidémiologie moléculaire d'un champignon causant la rouille des feuilles du peuplier, Melampsora medusae f. sp. deltoidae, en amérique du nord

Because Melampsora medusae is an obligate parasite able to reproduce both sexually and asexually, two main sources may be considered as origin of primary inoculum in North America. Where the sympatry hosts are poplar (Populus deltoides) and larch (Larix laricina ), sexual reproduction is possible, and the primary inoculum is presumed to be ecidiospores produced on larch. The other potential source of primary inoculum is urediniospores produced through asexual reproduction on poplars. This source of inoculum could mainly originate from allopatry, where larch is absent.

Considering the hypothesis of two poles of origin, populations of sympatry should reveal a genetic structure reflecting the occurrence of sexual reproduction, that is an important genetic diversity and a low level of clonality, whereas in allopatry the reverse situation would be expected. Moreover, sympatry and allopatry should show the presence of distinct alleles.

To test this hypothesis, two polymorphic loci of M. medusae f. sp. deltoidae were identified by cloning. For each locus, one PCR-SSCP (Polymerase Chain Reaction - Single-Strand Conformational Polymorphism) marker was designed. (Abstract shortened by UMI.)