Using mating-type loci to improve taxonomy of the Tuber indicum complex, and discovery of a new species, T. longispinosum

Three New Truffle Species (Tuber, Tuberaceae, Pezizales, and Ascomycota) from Yunnan, China, and Multigen Phylogenetic Arrangement within the Melanosporum Group

Based on a multi-locus phylogeny of a combined dataset of ITS, LSU, tef1-α, and rpb2 and comprehensive morphological analyses, we describe three new species from the Melanosporum group of genus Tuber and synonymize T. pseudobrumale and T. melanoexcavatum. Phylogenetically, the three newly described species, T. yunnanense, T. melanoumbilicatum and T. microexcavatum, differ significantly in genetic distance from any previously known species. Morphologically, T. yunnanense is distinctly different from its closest phylogenetically related species, T. longispinosum, due to its long shuttle-shape spores (average the ratio of spore length to spore width for all spores (Qm) = 1.74). Tuber melanoumbilicatum differs from the other species in having a cavity and long shuttle-shaped spores (Qm = 1.65). Although T. microexcavatum sampled ascomata have relatively low maturity, they can be distinguished from its closely related species T. pseudobrumale by the ascomata size, surface warts, and spore number per asci; additionally, phylogenetic analysis supports it as a new species. In addition, molecular analysis from 22 newly collected specimens and Genebank data indicate that T. pseudobrumale and T. melanoexcavatum are clustered into a single well-supported clade (Bootstrap (BS) = 100, posterior probabilities (PP) = 1.0); and morphological characteristics do not differ. Therefore, based on the above evidence and publication dates, we conclude that T. melanoexcavatum is a synonym of T. pseudobrumale. By taking into account current knowledge and combining the molecular, multigene phylogenetic clade arrangement and morphological data, we propose that the Melanosporum group should be divided into four subgroups. Diagnostic morphological features and an identification key of all known species in the Melanosporum group are also included. Finally, we also provide some additions to the knowledge of the characterization of T. pseudobrumale, T. variabilisporum, and T. pseudohimalayense included in subgroup 1 of the Melanosporum group.

Tuber eburneum and Tuber mujicii: New pine-associated Tuber species from eastern North America

The ectomycorrhizal truffle genus Tuber is widespread and diverse. Recent sampling of ascomata, ectomycorrhizal root tips, and environmental sequences has resulted in the identification of many Tuber species that cannot be assigned to described species and require formal description. Using morphological and molecular phylogenetic analysis, we describe two North American Tuber species associated with pines (Pinus spp.). Tuber eburneum, sp. nov., is an early-diverging taxon in the Melanosporum clade that differs substantially from all other taxa in that clade due to its light-colored peridium and gleba, lack of peridial warts, and peridial hairs that are ornamented with small, irregular protrusions. Tuber mujicii, sp. nov., is a whitish truffle species in the Puberulum clade. Although T. mujicii is morphologically similar to many related taxa, it can be distinguished by a combination of characters, including peridium color, spore size, number of ascospores per ascus, and number of reticulations across the spore surface.

Tuber torulosum: A new truffle species decorated with moniliform cystidia from Japan

We describe a new truffle species, Tuber torulosum, based on molecular and morphological analyses. This species forms a single globose ascospore per ascus, pale yellow in color, as do Japanese T. flavidosporum and Chinese T. turmericum and T. xanthomonosporum in the Japonicum clade of the Tuber phylogeny. However, it can be distinguished from them microscopically by its whitish tomentose mycelium that partially covers the ascoma surface and the mesh size of its spore ornamentation. Cystidia are moniliform and yellowish to reddish. Molecular phylogenetic analysis using the internal transcribed spacer and partial large subunit regions of ribosomal DNA also supports T. torulosum as a distinct species. On the basis of our results, we provide a key to species in the Japonicum clade.

Life Cycle and Phylogeography of True Truffles

True truffle (Tuber spp.) is one group of ascomycetes with great economic importance. During the last 30 years, numerous fine-scale population genetics studies were conducted on different truffle species, aiming to answer several key questions regarding their life cycles; these questions are important for their cultivation. It is now evident that truffles are heterothallic, but with a prevalent haploid lifestyle. Strains forming ectomycorrhizas and germinating ascospores act as maternal and paternal partners respectively. At the same time, a number of large-scale studies were carried out, highlighting the influences of the last glaciation and river isolations on the genetic structure of truffles. A retreat to southern refugia during glaciation, and a northward expansion post glaciation, were revealed in all studied European truffles. The Mediterranean Sea, acting as a barrier, has led to the existence of several refugia in different peninsulas for a single species. Similarly, large rivers in southwestern China act as physical barriers to gene flow for truffles in this region. Further studies can pay special attention to population genetics of species with a wide distribution range, such as T. himalayense, and the correlation between truffle genetic structure and the community composition of truffle-associated bacteria.

Tuber iryudaense and T. tomentosum: Two new truffles encased in tomentose mycelium from Japan

We describe two new Japanese truffle species, Tuber iryudaense and Tuber tomentosum, based on molecular and morphological analyses. Both species are clearly distinguishable from other Tuber species by the ocher tomentose mycelium covering the ascoma surfaces. Tuber iryudaense has one-spored asci that each contain a large (68-97 × 51-80 µm), reddish-brown ascospore; these microscopic characters are similar to those of closely related Chinese species, T. calosporum, T. gigantosporum, T. glabrum, T. monosporum, and T. sinomonosporum. Tuber tomentosum forms one to four ascospores per ascus with a reddish-brown color similar to that of ascospores of T. macrosporum and T. canaliculatum, although their spores are much larger than those of T. tomentosum (27‒64 × 26‒55 µm). Molecular phylogenetic analyses based on ribosomal internal transcribed spacer and partial 28S nuc rDNA sequences support that both species are distinct within the Macrosporum group.

Phylogenetic placements and cultural characteristics of Tuber species isolated from ectomycorrhizas

Pure cultures of Tuber were isolated from ectomycorrhizal root tips in Abies sachalinensis plantations in Hokkaido, Japan. Their phylogenetic relationships as well as vegetative hyphal characteristics on culture media were reported. Phylogenetic analysis based on the internal transcribed spacer within ribosomal DNA settled well-supported eight lineages within Puberulum, Latisporum, and Maculatum clades in Tuber. Three and one lineages were grouped with undescribed species of Puberulum clade in Japan and that of the Latisporum group in China, respectively. Two lineages were closely associated to but distinct from an undescribed species of Puberulum clade in Japan. One lineage did not group with any sequences in the International Nucleotide Sequence Database (INSD), proposing a new taxon in the Latisporum group. One lineage was grouped with T. foetidum in Maculatum clade. All strains in each lineage displayed yellowish white, thin, filamentous colonies on Melin-Norkrans agar medium. Various differences in morphological characteristics of hyphae on pure cultures of various strains were noted, but they were frequently uncommon among strains of the same taxa. Isolation from ectomycorrhizal root tips can be among the effective ways to acquire pure cultures of Tuber strains.

Rapid MALDI-TOF MS identification of commercial truffles

Truffles are edible mushrooms with similar morphological characteristics, that make it difficult to distinguish between highly prized truffles (such as the Périgord black T. melanosporum) and inexpensive truffles (such as the Asian Black T. indicum). These biological and economic features have led to several misidentifications and/or fraudulent profit in the truffle markets. In this paper, we investigate Matrix-assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS) biotyping to identify 34 commercial fresh truffles from Europe and Asia. The MALDI-TOF MS clustering rapidly distinguished seven Tuber species identified by ITS phylogenetic analysis. The tasty T. melanosporum was clearly differentiated from the Chinese and less expensive truffles. These cheaper mushrooms were marketed as T. indicum but corresponded to a mix of three species. In total, the method confirmed misidentifications in 26% of commercial specimens. Several unknown blind-coded truffles were rapidly identified, with scores >= 2, using the Bruker Biotyper algorithm against MS databases. This study demonstrates that MALDI-TOF MS is a reliable, rapid and cheaper new tool compared with molecular methods for the identification of truffle species and could be used to control frauds in the truffle markets. It could also be useful for the certification of truffle-inoculated seedlings and/or diversity in forest ecosystems.

Ectomycorrhizae formed by three Japanese truffle species (Tuber japonicum, T. longispinosum, and T. himalayense) on indigenous oak and pine species

Modern truffle cultivation systems started in Europe in the early 1970s and are now successfully used for several European truffles throughout the world. However, systems for indigenous novel truffle species need to be developed in several regions, especially where truffle cultivation has not been attempted so far, such as in Japan. Recently, two new and one known truffle species that are expected to be edible were reported from Japan: Tuber japonicum, T. longispinosum, and T. himalayense. Here, we conducted mycorrhization trials between these three truffle species and four native tree species in Japan (Quercus acutissima, Q. phillyraeoides, Q. serrata, and Pinus densiflora) using spore suspension and trap-plant seedling techniques under axenic pot culture conditions to understand their potential host ranges and mycorrhizal morphologies and to determine whether these inoculation methods are applicable for mycorrhization of Japanese truffles with native host plants. Of the 12 combinations, nine were successful for mycorrhization, including both oak and pine trees. The T. japonicum mycorrhiza was characterized by short, needle-shaped cystidia without septa, whereas the two black truffles, T. longispinosum and T. himalayense, were indistinguishable from each other because they shared the same morphological and anatomical characters such as brownish, long cystidia with right angle ramification. These features were similar to related black truffle species. The results of the present study indicate that the inoculation method used for European truffles can also be applied for mycorrhization between Japanese truffle species and compatible native pine and/or oak hosts in Japan.

Studies on diversity of higher fungi in Yunnan, southwestern China: A review

Yunnan is exceedingly rich in higher fungi (Ascomycota and Basidiomycota). Given that the number of fungi (including lichens) occurring in a given area is, as Hawksworth suggested, roughly six times that of local vascular plants, a total of approximately 104,000 fungal species would be expected in Yunnan. However, to date only about 6000 fungal species, including roughly 3000 species of higher fungi, have been reported from the province. Although studies on Yunnan's fungi started in the late nineteenth century, significant progress has been made only in the last forty-five years. Over the first twenty-five years of this period, studies on fungal diversity in this area have largely been about taxonomy based on morphological characters and partially on geographical distribution. Over the past twenty years, the combination of both morphological and molecular phylogenetic approaches has become the preferred method to help understand the diversity and evolution of higher fungi. This review focuses on our current knowledge of how geological, geographical, and ecological factors may have contributed to the diversity patterns of higher fungi in Yunnan. Based on this knowledge, three aspects for future studies are suggested.