Hypogeous Pezizaceae: Physiology and Molecular Genetics

With the exception of the forest truffles, which belong to the Tuberaceae family, truffle members of the order Pezizales may be said to have been rather neglected by science. The limited research that has been done on non-Tuberacean hypogeous mushrooms of the Pezizales, which include the desert truffles, has mostly focused on Phylogenetic aspects. Traditionally, the assignment of a particular family and species of the truffle genera to a particular genus was based on morphological parameters of the ascomata, asci and spores (Trappe 1979). In recent years, however, molecular Phylogenetic research on sequestrate fungi has repeatedly demonstrated that the morphology of hypogeous fungi can be misleading due to reduction in macromorphological characters needed for distinguishing their related epigeaous taxa. Molecular analyses of members of the Pezizales and of the Phylogenetic relations among epi- and hypogeous species have been conducted by O’Donnell et al. (1997), Norman and Egger (1999), Percudani et al. (1999), Roux et al. (1999), Hansen et al. (2001) and Diez et al. (2002). Some of these investigations validate earlier morphological findings. Thus, O’Donnell et al. (1997) and Hansen et al. (2001) demonstrated that certain hypogeous members of the Pezizales show greater affinity to epigeous members than to other hypogeous species. Similarly, the monophyletic origin of some members of Terfezia and Tirmania was substantiated by Diez et al. (2002). However, other results have upset some of the earlier placements. For example, along with Tirmania, Terfezia was shown to belong to the Pezizaceae rather than to the distinctly hypogeous Terfeziaceae family, which was therefore abolished (Norman and Egger 1999; Percudani et al. 1999). The genus Choiromyces was transferred from the Pezizaceae (Terfeziaceae) to the Tuberaceae (O’Donnell et al. 1997; Percudani et al. 1999), although one Choiromyces species, C. echinulatus, was excised from this genus and restored to the Pezizaceae under a new name, Eremiomyces echinulatus (Ferdman et al. 2005). Similarly, two species were removed from the Terfezia genus: Terfezia terfezioides, reinstated as Mattirolomyces terfezioides (Percudani et al. 1999; Diez et al. 2002), and Terfezia pfeilii, renamed Kalaharituber pfeilii (Ferdman et al. 2005). Cryptic species are coming to light, including a group of three discovered in the T. boudieri desert truffle complex (Ferdman 2006). Moreover, new mycorrhizal species were recently identified among the Pezizales (Tedersoo et al. 2006).