Résumé:
The study is conducted in two growing areas of garden pea (Pisum
sativum L.) in northwestern Algeria. Damages caused by Ascochyta sp
complex are important in particular for the variety of Kelvedon Wonder.
Observations carried out on the infected plants for several years, indicate the
presence of superimposed necrosis of different sizes on all aerial organs.
However, these observations do not differentiate symptoms by species. The
results of morphological and molecular characterization with sequencing in
internal transcribed spacer (ITS) regions and inoculation tests on 32 isolates
in the laboratory of symbiosis and plant pathology from Toulouse (France),
show a reconciliation of the sequencing by polymerase chain reaction (PCR)
products and size necrosis for all Ascochyta pinodes and pinodella. Alone,
Ascochyta pisi is distinguished by a smaller size necrosis. On the molecular
level, all isolates whose ITS regions were amplified by PCR, expresses
similar size products (550 bp). This molecular weight is found on a large set
of pathogenic fungi. The three species of Ascochyta sp complex do not exhibit
polymorphism for Pisum sativum species and have an identical molecular
weight. The pathogenicity tests performed showed differences in
aggressiveness on the host plant. Ascochyta pinodes is the most aggressive
than the other two species. As a result, it causes more damage to the crop.
