Tuber brennemanii and Tuber floridanum: Two new Tuber species are among the most commonly detected ectomycorrhizal taxa within commercial pecan (Carya illinoinensis) orchards.

Truffles are sequestrate hypogeous fungi, and most form ectomycorrhizal (ECM) associations with trees. Truffles belonging to the genus Tuber (Pezizales, Ascomycota), "true truffles," associate with diverse plant hosts, including economically important species such as pecan (Carya illinoinensis). Morphological and phylogenetic studies delimited several major lineages of Tuber, which include many cryptic and undescribed species. One of these, the Maculatum clade, is a speciose group characterized by relatively small, light-colored ascomata that have alveolate-reticulate spores. Here, we describe two new species in the Maculatum clade, Tuber brennemanii and T. floridanum (previously identified as Tuber sp. 36 and Tuber sp. 47). We delineate these two species by phylogenetic analyses of nuc ITS1-5.8S-ITS2 (= ITS) and partial 28S rDNA (= LSU), and through morphological analysis. A recent collection of T. floridanum from a pecan orchard in Brazil indicates that this species was introduced there on the roots of pecan seedlings. Systematic studies of ascomata and ECM fungal communities indicate that these species are geographically widespread and common ECM symbionts of pecans and other members of the Fagales, particularly in sites with disturbed soils and nutrient enrichment.

Tuber aztecorum sp. nov., a truffle species from Mexico belonging to the Maculatum clade (Tuberaceae, Pezizales).

A new species of truffle, T. aztecorum, is described from central Mexico. Tuber aztecorum can be distinguished from other related Tuber species synoptically by a combination of morphological features including ascospore size, pellis cells with irregular thickness, cystidia, ascoma colour and associated host (Abies religiosa an endemic Abies species from central Mexico); sequence variation on the ITS rDNA also distinguishes T. aztecorum from related species. A phylogenetic analysis of the ITS rDNA demonstrates that T. aztecorum belongs to the Maculatum clade and is unique from other similar small, white-cream coloured Tuber species distributed in north-eastern Mexico such as T. castilloi and T. guevarai.

New Boletaceae taxa from Guyana: Binderoboletus segoi gen. and sp. nov., Guyanaporus albipodus gen. and sp. nov., Singerocomus rubriflavus gen. and sp. nov., and a new combination for Xerocomus inundabilis.

Binderoboletus segoi gen. and sp. nov., Guyanaporus albipodus gen. and sp. nov. and Singerocomus rubriflavus gen. and sp. nov. (Boletaceae, Boletales, Basidiomycota) are described from the Pakaraima Mountains and adjacent lowlands of Guyana. Xerocomus inundabilis, originally described from the central Brazilian Amazon and based solely on the type collection, is redescribed from numerous collections from Guyana and transferred into Singerocomus. These boletes occur in Neotropical forests dominated by ectomycorrhizal trees in the genera Dicymbe (Fabaceae subfam. Caesalpinioideae), Aldina (Fabaceae subfam. Papilionoideae) and Pakaraimaea (Dipterocarpaceae). Three of the species were repeatedly found in a multiyear sporocarp survey in Dicymbe corymbosa-monodominant forest. Macromorphological, micromorphological, habitat and multilocus DNA sequence data are provided for each species. A molecular phylogenetic analysis based on a large taxon set across the Boletaceae justifies erection of the new genera.

New species of Xerocomus (Boletales) from the Guiana Shield, with notes on their mycorrhizal status and fruiting occurrence.

Xerocomus cyaneibrunnescens, Xerocomus potaroensis, and Xerocomus parvogracilis (Boletales, Basidiomycota) are described as new species from the Pakaraima Mountains of Guyana, in the central Guiana Shield region. These boletes occur in neotropical forests dominated by ectomycorrhizal (ECM) trees in the genus Dicymbe (Fabaceae subfam. Caesalpinioideae). Each species produced basidiomata during a multi-year plot survey, and each was confirmed as an ECM symbiont with one or more leguminous host plant species in Guyana.

New North American truffles (Tuber spp.) and their ectomycorrhizal associations.

Recent surveys of belowground fungal biodiversity in México and USA have revealed many undescribed truffle species, including many in the genus Tuber. Here we describe seven new species: Tuber beyerlei, T. castilloi, T. guevarai, T. lauryi, T. mexiusanum, T. miquihuanense and T. walkeri. Phylogenetic analyses place these species within the Maculatum group, an understudied clade of small truffles with little apparent economic value. These species are among the more taxonomically challenge-ing in the genus. We collected Tuber castilloi, T. mexiusanum and T. guevarai as fruit bodies and ectomycorrhizae on Quercus spp. in forests of eastern México. Tuber mexiusanum has a particularly broad geographic range, being collected in eastern USA under Populus deltoides and in Minnesota and Iowa in mixed hardwood forests. T. walkeri is described from the upper midwestern USA, and T. lauryi and T. beyerlei occur in the western USA.