Taxonomy, Biology and Ecology of Tuber macrosporum Vittad. and Tuber mesentericum Vittad

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.

Soil temperature and hydric potential influences the monthly variations of soil Tuber aestivum DNA in a highly productive orchard

Tuber aestivum, also known as the summer or Burgundy truffle, is an ectomycorrhizal Ascomycete associated with numerous trees and shrubs. Its life cycle occurs in the soil, and thus soil parameters such as temperature and water availability could influence it. T. aestivum cultivation has started in several countries, but ecological and agronomic requirements for the establishment and management of orchards are largely unknown. The aims of this work were: 1) to design a specific qPCR protocol using genomic data to trace and quantify T. aestivum DNA in the soil; and 2) to assess the monthly soil DNA dynamic according to soil parameters (i.e. soil hydric potential and temperature) in this orchard. The study was conducted in a highly productive T. aestivum orchard (hazels, oaks, pines, lime and hornbeam). The production started five years after the plantation and then increased exponentially to reach a maximum of 320 kg/ha in 2017. The soil hydric potential and temperature partially explained the monthly T. aestivum soil DNA variability. The data presented here offer new insights into T. aestivum ecology and cultivation.

Multi-cropping edible truffles and sweet chestnuts: production of high-quality Castanea sativa seedlings inoculated with Tuber aestivum, its ecotype T. uncinatum, T. brumale, and T. macrosporum

The plantation and management of sweet chestnut (Castanea sativa Mill.) orchards is a common and traditional land use system in many areas of Europe that offers the advantage of simultaneous production of nuts and timber. During the last decades, sweet chestnut has declined dramatically in many regions because of the profound social changes in rural areas coupled with pathogen attacks. Truffles, the hypogeous ascocarps of the ectomycorrhizal genus Tuber, are currently cultivated using host trees inoculated with these fungi for improving production in truffle orchards. The production of good forestry quality chestnut seedlings inoculated with European truffles in nurseries is essential for multi-cropping plantation establishment, but so far, it has not been implemented in agroforestry practices. Moreover, it is necessary to assess the physiological condition of the seedlings due to the high calcium amendment needed for the growth of Tuber spp. mycelium that can become toxic for the host plants. In this study, seedlings of C. sativa were inoculated with Tuber aestivum and its ecotypes T. uncinatum, T. brumale, and T. macrosporum and were grown in a greenhouse using culture conditions favorable for the production of high-quality plants for forestry purposes. At the end of the assay, levels of root colonization and morphological and physiological parameters of the seedlings were measured. The colonization of C. sativa with T. aestivum, its ecotype T. uncinatum, and T. brumale was successful, and the seedlings showed normal growth. Inoculation protocols with T. macrosporum need to be improved. Tuber species formed well-developed ectomycorrhizae on C. sativa in nursery conditions.