Les champignons parasites du Cèdre de l'Atlas en Afrique du nord et en France.

Les auteurs ont recensé 44 espèces de parasites du Cèdre de l'Atlas en Afrique du nord et en France qui se répartissent en : 21 Deutéromycètes, 10 Ascomycètes, 9 Basidiomycètes, 2 Oomycètes, 2 Zygomycètes

Biodiversité et dynamique de la végétation dans la subéraie de la Maâmora (Maroc), effet de la durée de clôture.

La subéraie de la Maâmora au Maroc, abrite une flore très riche et variée. Elle subit cependant de nombreuses contraintes, notamment anthropiques. Cette étude sur l'évolution de la biodiversité permet la comparaison très précises de parcelles clôturées et non clôturées, afin d'évaluer le rôle de la mise en défens sur l'évolution de la végétation

Croissance et assimilation des nitrates chez le champignon ectomycorhizien Pisolithus tinctorius

Huit variétés de champignon ectomycorhizien P. tinctorius ont été utilisées pour l'étude de l'assimilation de l'azote nitrique. Les résultats obtenus montrent que l'absorption des nitrates est différente en fonction de la variété utilisée. L'étude de la croissance des huit variétés montre que le diamètre moyen de Pt1, Pt2, Pt5 et Pt7 atteint des valeurs comprises entre 7 et 8,66 cm alors que celui de Pt3, Pt4, Pt6 et PUO ne dépasse pas 6,76 cm. La production de biomasse coïncide généralement avec la croissance radiale à l'exception de Pt7 dont l'intensité (faible) et la n~ture (fine) des filaments ne permettent pas une production mycéliale à l'image de la croissance radiale. En effet, la biomasse de cette variété obtenue après un mois de culture n'excède pas 143 mg de mycélium frais, ce qui correspond à 35,5 % seulement de la moyenne des quantités produites par les autres variétés. L'activité nitrate réductase a été mesurée in vivo sur des thalles cultivés sur milieu MNM(N03). L'évolution de l'ANR en fonction de l'âge du champignon, de la durée d'incubation, du pH, de la température et de la concentration en nitrates du milieu a permis de définir les conditions expérimentales qui améliorent très nettement l'activité de la nitrate réductase

Diversity of arbuscular mycorrhizal fungi in Tetraclinis articulata (Vahl) Masters woodlands in Morocco

A survey of arbuscular mycorrhizal (AM) fungi was conducted in seven Tetraclinis woodlands. Microscopic analysis of the mycorrhizal status of T. articulata (Vahl) Masters roots revealed that all samples formed only AM, and no ectomycorrhizal fungi were detected. The mycorrhizal colonisation level was generally high (more than 80%), thus reflecting the mycotrophic nature of T. articulata. A "Paris-type" mycorrhizal structure was noted in all studied samples. The number of AM fungal spores detected in field-collected soils was relatively high. All recovered spores belonged to the Glomineae order, represented by Glomaceae and Acaulosporaceae families. Two groups were dominant: the first one included small (90 mu m), hyaline, white to dark-yellow spores, and the second involved large (295 mu m), light orange to dark orange-brown spores. The morphological characters indicated that the spore populations consisted of 3-6 morphotypes. The Glomus genus was represented by five species, i.e. Glomus aggregatum, Glomus constrictum, Glomus sp. 1, Glomus sp. 2, and Glomus sp. 3, while the Acaulospora genus was represented by only one unidentified species

Phylogenetic diversity of Moroccan cork oak woodlands fungi

Interspecific variation among 87 sporocarps of fungi belonging to 15 genera and 39 species were evaluated by analyzing the internal transcribed spacer (ITS) of the rDNA region using restriction fragment length polymorphism (RFLP). The ITS region was first amplified by polymerase chain reaction (PCR) with specific primers and then cleaved with different restriction enzymes. Amplification products, which ranged between 500 and 950 base pairs (bp), were obtained for all the isolates analyzed. The degree of polymorphism observed did not allow proper identification of most of the species. Cleavage of amplified fragments with the restriction enzymes Alu I, EcoR I and Hinf I revealed extensive polymorphism. The fifteen genera and most species presented specific restriction patterns. The only species not identifiable by a specific pattern belonged to the genera Russula (R. decipiens and R. straminea). These species might be considered as closely related species. The Pisolithus sporocarps had two ITS-RFLP types with one dominating. ITS sequencing confirms that the two RFLP types correspond to two distinct species of Pisolithus. Our data show the potential of ITS region PCR-RFLP for the molecular characterization of ectomycorrhizal fungi and their identification and monitoring in artificial inoculation programs

Molecular phylogeny of Pisolithus species from Moroccan forest woodlands

The phylogenetic relationships among 200 Pisolithus basidiomata collected from pine, oak, and eucalypt forests and rockrose scrubs in Morocco were investigated. Using PCR-RFLP analysis of the internal transcribed spacer (ITS) of ribosomal DNA, this collection could be divided into 5 groups, by using PCR-RFLP analysis of the internal transcribed spacer (ITS) of ribosomal DNA. The ITS of a representative basidioma of each group was sequenced, and a phylogenetic analysis was performed. The dendrogram suggests that at least five Pisolithus species are present in Morocco. Pisolithus basidiomata collected in the Pinus and Quercus forests correspond to Pisolithus arrhizus and P. species 4 as previously described by Martin and colleagues in 2002. Those collected from the eucalyptus forests, under E. gomphocephala and E. camaldulensis, correspond to P. albus and P. microcarpus. Basidiomata collected from the rockrose scrubs, under Cistus crispus, C. monspeliensis or C. salviifolius, are all identified as Pisolithus species 3. Phylogenetic analyses showed that our different Pisolithus grouped well with Pisolithus specimens from other geographical origins