Penicillium nodositatum induces the formation of nodules
on the
roots of Alnus. The analysis of RFLPs in the PCR-amplified
ITS1-5·8S-ITS2
ribosomal sequence demonstrates that all the nodule-inducing strains isolated
belong to a homogeneous taxon,
P. nodositatum, distinct from other morphologically close species
of Penicillium. A gene tree inferred from the ITS1-5·8S-ITS2
PCR/RFLP data shows that the P. nodositatum sequence clusters
with
those of Penicillium species belonging to subgenus Biverticillium.
RAPDs generated using four 10-mer primers, allowed us to identify four
distinct
groups of strains in a sample of 28 strains of
P. nodositatum collected in 10 different geographic sites. Only
one
group was found in each sampled site. No link could be
established between RAPD-based groups and the geographic origin of the
strains.
However, our results suggest a possible link
between these groups and Alnus species and/or habitats associated
with each of the four French Alnus species.