Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → Belgique → Caractérisations morphologique, biologique et moléculaire de souches de Phytophthora nicotianae responsables d’un syndrome associant nécroses racinaires et flétrissement du piment (Capsicum annuum L.) en Tunisie.

Faculté des Sciences Agronomiques (Gembloux) 2000

Caractérisations morphologique, biologique et moléculaire de souches de Phytophthora nicotianae responsables d’un syndrome associant nécroses racinaires et flétrissement du piment (Capsicum annuum L.) en Tunisie.

ALLAGUI M. Bechir

Titre : Caractérisations morphologique, biologique et moléculaire de souches de Phytophthora nicotianae responsables d’un syndrome associant nécroses racinaires et flétrissement du piment (Capsicum annuum L.) en Tunisie.

Auteur : ALLAGUI M. Bechir

Université de soutenance : Faculté des Sciences Agronomiques (Gembloux)

Grade : Doctorat 2000

Résumé (UniCat)
Root and crown rots associated with wilt of pepper cause severe losses in the main areas of production in Tunisia. Previous studies showed that the symptoms were due to a pathogen belonging to Phytophthora genus, but controversy remains about the species involved. Our identification based on the classic taxonomy of Phytophthora species showed that the causative agent of the disease belongs to Phytophthora nicotianae var. parasitica sensu Stamps et al. (1990). PCR amplification of the ITS, ITS-I and ITS-II regions in the rDNA revealed that the amplified products generated by pepper isolates of Phytophthora were about 900 bp, 310 bp and 600 bp respectively ; these sizes were identical to those produced by the reference isolates of P. nicotianae but different from those produced by P. capsici. The ITS amplicons digested by 8 endonucleases did not show any difference between pepper isolates of Phytophthora and P. nicotianae. The inoculation of pepper isolates of Phytophthora on tomato, eggplant and tobacco showed that the parasitic form was not pathogen to tobacco, while its pathogenicity on tomato and eggplant was weak and associated with atypical symptoms not observed in the field. These results indicate an adaptation of pepper isolates of Phytophthora on this plant. Based on the particularities observed in the morphologic, biologic and molecular criteria, we suggest that the pepper isolates of Phytophthora constitute a new forma specialis on pepper to which we propose the name Phytophthora nicotianae f. sp. tunisiana. The inoculation method developed will permit to set up genetic strategy to control the disease by exploiting the resistance identified in the CM 334 variety.

Mots clés : Nécrose --- Racine --- Flétrissement --- Symptome --- Capsicum annuum --- Phytophthora infestans --- Marqueur génétique --- Biologie moléculaire

Page publiée le 30 octobre 2015, mise à jour le 25 janvier 2017