Six Cistaceae species, Helianthemum ledifolium, Helianthemum lippii, Fumana procumbens, Cistus albidus, Cistus incanus, Cistus salvifolius, and Pinus halepensis (Aleppo pine) were inoculated with three mycorrhizal desert truffles, Terfezia leptoderma, Terfezia boudieri, and Terfezia claveryi under greenhouse conditions, on soil originating from desert truffle natural habitat in Algeria. The syntheses have led to the formation of typical endomycorrhizae in annual Cistaceae (H. ledifolium) and perennial ones (H. lippii and F. procumbens) and an ectomycorrhiza with a less developed sheath in Cistus species and Aleppo pine. These results demonstrate the plasticity of Terfezia species to form different mycorrhizal types. The formation of an endomycorrhiza with H. ledifolium and F. procumbens and a sheathing ectomycorrhiza with P. halepensis inoculated by T. leptoderma in in vivo culture conditions was obtained for the first time.

Morphological and phylogenetic analyses of large ribosomal subunit (28S rDNA) and internal transcribed spacer (ITS rDNA) of Terfezia samples collected from several bioclimatic zones in Algeria and Spain revealed the presence of six distinct Terfezia species: T. arenaria, T. boudieri, T. claveryi; T. eliocrocae (reported here for the first time from North Africa), T. olbiensis, and a new species, T. crassiverrucosa sp. nov., proposed and described here, characterized by its phylogenetic position and unique combination of morphological characters. A discussion on the unresolved problems in the taxonomy of the spiny-spored Terfezia species is conducted after the present results.

The species concept within the genus Picoa Vittad. is here revisited in light of new molecular and ecological data obtained from samples collected throughout the Mediterranean basin. Two highly diverse widespread clades and four additional minor lineages were significantly supported by three genes dataset (ITS, 28s LSU and RPB2) inferences for 70 specimens. The two widespread clades occur in very different geographical and ecological areas associated with exclusive host plants in the genus Helianthemum. SEM study of spore surface morphology in these lineages revealed the existence of smooth ascospores in the majority of these clades. However the most frequent lineage in Europe and coastal North Africa displayed either smooth or verrucose spores. Hence this morphological criterion cannot be reliably used to discriminate between the different clades. In addition, SEM observations made on ascospores from several original collections of P. juniperi and P. lefebvrei supported the hypothesis that ornamentation depends on the degree of maturity in some of these lineages. Geographical and ecological, rather than morphological data are here suggested as the most useful characters to separate the different lineages in Picoa. Further studies focusing on these features are needed before the names P. juniperi and P. lefebvrei can be unambiguously linked with the genetic lineages observed.

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This study presents the first evidence of the mycorrhizal compatibility between the edible desert truffle Tirmania nivea and the valuable fruit tree Argania spinosa. Seed germination trials demonstrated that soaking pre-treatment of argan seeds in hydrogen peroxide (9%) for five days combined with the application of a fungicide treatment on an inert sowing material maximized the seed germination of this tree species. The mycorrhizal synthesis was conducted under greenhouse conditions by inoculating, in vivo, the host plant seedlings with spores of T. nivea. The growth and mycorrhizal status of A. spinosa was assessed 15.5 months after inoculation. The desert truffle mycorrhization significantly promoted all the investigated morphological parameters of growth and improved the physiological performances of the host plant through enhancing plant water status and chlorophyll concentration. The mycorrhizal symbiosis led to the formation of typical desert truffle endomycorrhizae with intracellular coils. The resistance of A. spinosa to the harsh environmental conditions of desert habitats makes it a potential candidate for cultivation of desert truffles.