Graduate Thesis Or Dissertation

Taxonomy of desert truffles : the genera Phaeangium and Tirmania

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  • Mycorrhizal fungi are important in food production of arid lands. The desert truffles not only form a symbiotic association with range plants but also form fruiting bodies which are both prized as food and nutritious. The taxonomy and ecology of two genera of desert truffles are treated in this thesis. The genus Phaeangium containing the sole species P. lefebvrei Pat., occurs from Algeria East to the Arabian Penninsula. It has been variously interpreted by past authors. Most placed it in the genus Picoa, which is characterized by a verrucose ectal excipulum and smooth spores. P. lefebvrei, however, proves to have minutely ornamented spores when fully mature, a feature overlooked in the past (most collections represented in herbaria are immature, and the spore ornamentation has not developed). In addition, it has a tomentum of surface-granulated hyphae. P. lefebvrei is redescribed and placed in the family Pyronemataceae (Pezizales). It is novel in being commonly scratched out of the soil and eaten by birds, which probably thereby disperse the spores. It is likely a mycorrhizal fungus with annual Helianthemum spp. The genus Tirmania contains two species, T. nivea (Desf. ex Fr.) Trappe and T. pinoyi (Maire) Mal., which both occur from Morocco East to Iraq and the Arabian Penninsula. The genus is characterized by smooth sporocarps, asci which turn green to blue in Meizer's reagent, and double-walled spores with a smooth outer layer and a minutely reticulate-roughened inner layer. The two species are much alike, but T. nivea has ellipsoid spores and T. pinoyi has globose spores. Tirmania is placed in the family Pezizaceae (Pezizales). Both species produce large sporocarps that are collected and marketed as food. Their spores appear to be dispersed by abrasion of exposed, dried-in situ sporocarps by wind-blown sand. They are demonstrated mycorrhiza formers with annual Helianthemum spp.
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