Search

Desert truffle crop is a pioneer in southeastern Spain, a region where native edible hypogeous fungi are adapted to the semiarid areas with low annual rainfall.

The cultivation of desert truffle Terfezia claveryi using Helianthemum almeriense as a host plant has recently become a solid alternative crop in the Mediterranean region due to its adaptation to arid and semiarid ecosystems, which are expected to increase during the following years because of climate change. However, management models are still being developed in order to improve and stabilize the production, which varies greatly from one year to another. According to gatherers and farmers, one of the key factors for desert truffle production is the plant phenology in spring, which, in turn, depends on environmental conditions. In this manuscript, we have characterized the physiological, morphological, and molecular responses of the mycorrhizal plants in spring, coinciding with the fructification period of the plant and fungal species. Thanks to this characterization, a sigmoidal relationship between stomatal conductance and vapor pressure deficit (VPD) was found, which can be used as a marker of plant phenological switch. In order to confirm that this phenology status is related to desert truffle fructification, this marker has been successfully correlated to total truffle production. The results of this manuscript suppose a big step forward that will help to develop management models for the desert truffle crop.

Crous, P.W., Osieck, E.R., Jurjevi, Ž, Boers, J., Van Iperen, A.L., Starink-Willemse, M., Dima, B., Balashov, S., Bulgakov, T.S., Johnston, P.R., Morozova, O.V., Pinruan, U., Sommai, S., Alvarado, P., Decock, C.A., Lebel, T., McMullan-Fisher, S., Moreno, G., Shivas, R.G., Zhao, L., Abdollahzadeh, J., Abrinbana, M., Ageev, D.V., Akhmetova, G., Alexandrova, A.V., Altés, A., Amaral, A.G.G., Angelini, C., Antonín, V., Arenas, F., Asselman, P., Badali, F., Baghela, A., Bañares, A., Barreto, R.W., Baseia, I.G., Bellanger, J.-M., Berraf-Tebbal, A., Biketova, A. Yu., Bukharova, N.V., Burgess, T.I., Cabero, J., Câmara, M.P.S., Cano-Lira, J.F., Ceryngier, P., Chávez, R., Cowan, D.A., de Lima, A.F., Oliveira, R.L., Denman, S., Dang, Q.N., Dovana, F., Duarte, I.G., Eichmeier, A., Erhard, A., Esteve-Raventós, F., Fellin, A., Ferisin, G., Ferreira, R.J., Ferrer, A., Finy, P., Gaya, E., Geering, A.D.W., Gil-Durán, C., Glässnerová, K., Glushakova, A.M., Gramaje, D., Guard, F.E., Guarnizo, A.L., Haelewaters, D., Halling, R.E., Hill, R., Hirooka, Y., Hubka, V., Iliushin, V.A., Ivanova, D.D., Ivanushkina, N.E., Jangsantear, P., Justo, A., Kachalkin, A.V., Kato, S., Khamsuntorn, P., Kirtsideli, I.Y., Knapp, D.G., Kochkina, G.A., Koukol, O., Kovács, G.M., Kruse, J., Kumar, T.K.A., Kušan, I., Læssøe, T., Larsson, E., Lebeuf, R., Levicán, G., Loizides, M., Marinho, P., Luangsa-ard, J.J., Lukina, E.G., Magaña-Dueñas, V., Maggs-Kölling, G., Malysheva, E.F., Malysheva, V.F., Martín, B., Martín, M.P., Matočec, N., McTaggart, A.R., Mehrabi-Koushki, M., Mešić, A., Miller, A.N., Mironova, P., Moreau, P.-A., Morte, A., Müller, K., Nagy, L.G., Nanu, S., Navarro-Ródenas, A., Nel, W.J., Nguyen, T.H., Nóbrega, T.F., Noordeloos, M.E., Olariaga, I., Overton, B.E., Ozerskaya, S.M., Palani, P., Pancorbo, F., Papp, V., Pawłowska, J., Pham, T.Q., Phosri, C., Popov, E.S., Portugal, A., Pošta, A., Reschke, K., Reul, M., Ricci, G.M., Rodríguez, A., Romanowski, J., Ruchikachorn, N., Saar, I., Safi, A., Sakolrak, B., Salzmann, F., Sandoval-Denis, M., Sangwichein, E., Sanhueza, L., Sato, T., Sastoque, A., Senn-Irlet, B., Shibata, A., Siepe, K., Somrithipol, S., Spetik, M., Sridhar, P., Stchigel, A.M., Stuskova, K., Suwannasai, N., Tan, Y.P., Thangavel, R., Tiago, I., Tiwari, S., Tkalčec, Z., Tomashevskaya, M.A., Tonegawa, C., Tran, H.X., Tran, N.T., Trovão, J., Trubitsyn, V.E., Van Wyk, J., Vieira, W.A.S., Vila, J., Visagie, C.M., Vizzini, A., Volobuev, S.V., Vu, D.T., Wangsawat, N., Yaguchi, T., Ercole, E., Ferreira, B.W., de Souza, A.P., Vieira, B.S., Groenewald, J.Z. (2021): Fusarium chuoi R. Hill, Gaya, D.T. Vu, Sand.-Den. & Crous, R. Hill, Gaya, D.T. Vu, Sand.-Den. & Crous sp. nov. Fungal Planet 47 (1): 310-311, DOI: http://doi.org/10.5281/zenodo.5856199, URL: http://dx.doi.org/10.3767/persoonia.2021.47.06

Desert truffle is becoming a new crop in semiarid areas. Climatic parameters and the presence of microorganisms influence the host plant physiology and alter desert truffle production. Desert truffle plants present a typical summer deciduous plant phenology divided into four stages: summer dormancy, autumn bud break, winter photosynthetic activity, and spring fruiting. We hypothesize that the bacterial community associated with desert truffle plants will show a seasonal trend linked to their plant growth–promoting rhizobacteria (PGPR) traits. This information will provide us with a better understanding about its potential role in this symbiosis and possible management implementations. Bacteria were isolated from root-adhering soil at the four described seasons. A total of 417 isolated bacteria were phenotypically and biochemically characterized and gathered by molecular analysis into 68 operational taxonomic units (OTUs). They were further characterized for PGPR traits such as indole acetic acid production, siderophore production, calcium phosphate solubilization, and ACCD (1-amino-cyclopropane-1-carboxilatedeaminase) activity. These PGPR traits were used to infer functional PGPR diversity and cultivable bacterial OTU composition at different phenological moments. The different seasons induced shifts in the OTU composition linked to their PGPR traits. Summer was the phenological stage with the lowest microbial diversity and PGPR functions, whereas spring was the most active one. Among the PGPR traits analyzed, P-solubilizing rhizobacteria were harbored in the mycorrhizosphere during desert truffle fruiting in spring., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. MCIN/AEI/10.13039/501100011033 (Grant PID2020-115210RB-I00) and Fundación Séneca Agencia de Ciencia y Tecnología de la Región de Murcia (20866/PI/18). ALG was supported by Acción 6 program from University of Jaén.

The identity of the isotype specimen of Terfezia trappei (≡ Elaphomyces trappei) is studied with both morphological and molecular techniques. The obtained results demonstrate that T. trappei is a heterotypic synonym of Terfezia fanfani.

International audience; Desert truffles are edible hypogeous fungi forming ectendomycorrhizal symbiosis with plants of Cistaceae family. Knowledge about the reproductive modes of these fungi and the molecular mechanisms driving the ectendomycorrhizal interaction is lacking. Genomes of the highly appreciated edible desert truffles Terfezia claveryi Chatin and Tirmania nivea Trappe have been sequenced and compared with other Pezizomycetes. Transcriptomes of T. claveryi × Helianthemum almeriense mycorrhiza from well-watered and drought-stressed plants, when intracellular colonizations is promoted, were investigated. We have identified the fungal genes related to sexual reproduction in desert truffles and desert-truffles-specific genomic and secretomic features with respect to other Pezizomycetes, such as the expansion of a large set of gene families with unknown Pfam domains and a number of species or desert-truffle-specific small secreted proteins differentially regulated in symbiosis. A core set of plant genes, including carbohydrate, lipid-metabolism, and defence-related genes, differentially expressed in mycorrhiza under both conditions was found. Our results highlight the singularities of desert truffles with respect to other mycorrhizal fungi while providing a first glimpse on plant and fungal determinants involved in ecto to endo symbiotic switch that occurs in desert truffle under dry conditions.

Novel species of fungi described in this study include those from various countries as follows: Algeria, Phaeoacremonium adelophialidum from Vitis vinifera. Antarctica, Comoclathris antarctica from soil. Australia, Coniochaeta salicifolia as endophyte from healthy leaves of Geijera salicifolia, Eremothecium peggii in fruit of Citrus australis, Microdochium ratticaudae from stem of Sporobolus natalensis, Neocelosporium corymbiae on stems of Corymbia variegata, Phytophthora kelmanii from rhizosphere soil of Ptilotus pyramidatus, Pseudosydowia backhousiae on living leaves of Backhousia citriodora, Pseudosydowia indoor oopillyensis, Pseudosydowia louisecottisiae and Pseudosydowia queenslandica on living leaves of Eucalyptus sp. Brazil, Absidia montepascoalis from soil. Chile, Ilyonectria zarorii from soil under Maytenus boaria. Costa Rica, Colletotrichum filicis from an unidentified fern. Croatia, Mollisia endogranulata on deteriorated hardwood. Czech Republic, Arcopilus navicularis from tea bag with fruit tea, Neosetophoma buxi as endophyte from Buxus sempervirens, Xerochrysium bohemicum on surface of biscuits with chocolate glaze and filled with jam. France, Entoloma cyaneobasale on basic to calcareous soil, Fusarium aconidiale from Triticum aestivum, Fusarium juglandicola from buds of Juglans regia. Germany, Tetraploa endophytica as endophyte from Microthlaspi perfoliatum roots. India, Castanediella ambae on leaves of Mangifera indica, Lactifluus kanadii on soil under Castanopsis sp., Penicillium uttarakhandense from soil. Italy, Penicillium ferraniaense from compost. Namibia, Bezerromyces gobabebensis on leaves of unidentified succulent, Cladosporium stipagrostidicola on leaves of Stipagrostis sp., Cymostachys euphorbiae on leaves of Euphorbia sp., Deniquelata hypolithi from hypolith under a rock, Hysterobrevium walvisbayicola on leaves of unidentified tree, Knufia hypolithi and Knufia walvisbayicola from hypolith under a rock, Lapidomyces stipagrostidicola on leaves of Stipagrostis sp., Nothophaeotheca mirabibensis (incl. Nothophaeotheca gen. nov.) on persistent inflorescence remains of Blepharis obmitrata, Paramyrothecium salvadorae on twigs of Salvadora persica, Preussia procaviicola on dung of Procavia sp., Sordaria equicola on zebra dung, Volutella salvadorae on stems of Salvadora persica. Netherlands, Entoloma ammophilum on sandy soil, Entoloma pseudocruentatum on nutrient poor(acid)soil, Entoloma pudens on plant debris, amongst grasses. [...], Leslie W.S. de Freitas and colleagues express their gratitude to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for scholarships provided to Leslie Freitas and for the research grant provided to André Luiz Santiago; their contribution was financed by the projects ‘Diversity of Mucoromycotina in the different ecosystems of the Atlantic Rainforest of Pernambuco’ (FACEPE–First Projects Program PPP/ FACEPE/CNPq–APQ–0842-2.12/14) and ‘Biology of conservation of fungi s.l. in areas of Atlantic Forest of Northeast Brazil’ (CNPq/ICMBio 421241/ 2017-9) H.B. Lee was supported by the Graduate Program for the Undiscovered Taxa of Korea (NIBR202130202). The study of O.V. Morozova, E.F. Malysheva, V.F. Malysheva, I.V. Zmitrovich, and L.B. Kalinina was carried out within the framework of a research project of the Komarov Botanical Institute RAS (АААА-А19-119020890079-6) using equipment of its Core Facility Centre ‘Cell and Molecular Technologies in Plant Science’. The work of O. V. Morozova, L.B. Kalinina, T. Yu. Svetasheva, and E.A. Zvyagina was financially supported by Russian Foundation for Basic Research project no. 20-04-00349. E.A. Zvyagina and T.Yu. Svetasheva are grateful to A.V. Alexandrova, A.E. Kovalenko, A.S. Baykalova for the loan of specimens, T.Y. James, E.F. Malysheva and V.F. Malysheva for sequencing. J.D. Reyes acknowledges B. Dima for comparing the holotype sequence of Cortinarius bonachei with the sequences in his database. A. Mateos and J.D. Reyes acknowledge L. Quijada for reviewing the phylogeny and S. de la Peña- Lastra and P. Alvarado for their support and help. Vladimir I. Kapitonov and colleagues are grateful to Brigitta Kiss for help with their molecular studies. This study was conducted under research projects of the Tobolsk Complex Scientific Station of the Ural Branch of the Russian Academy of Sciences (N АААА-А19-119011190112-5). E. Larsson acknowledges the Swedish Taxonomy Initiative, SLU Artdatabanken, Uppsala (dha.2019.4.3-13). The study of D.B. Raudabaugh and colleagues was supported by the Schmidt Science Fellows, in partnership with the Rhodes Trust. Gregorio Delgado is grateful to Michael Manning and Kamash Pillai (Eurofins EMLab P&K) for provision of laboratory facilities. Jose G. Maciá-Vicente acknowledges support from the German Research Foundation under grant MA7171/1-1, and from the Landes-Offensive zur Entwicklung Wissenschaftlich-ökonomischer Exzellenz (LOEWE) of the state of Hesse within the framework of the Cluster for Integrative Fungal Research (IPF). Thanks are also due to the authorities of the Cabañeros National Park and Los Alcornocales Natural Park for granting the collection permit and for support during field work. The study of Alina V. Alexandrova was carried out as part of the Scientific Project of the State Order of the Government of Russian Federation to Lomonosov Moscow State University No. 121032300081-7. Michał Gorczak was financially supported by the Ministry of Science and Higher Education through the Faculty of Biology, University of Warsaw intramural grant DSM 0117600- 13. M. Gorczak acknowledges M. Klemens for sharing a photo of the Białowieża Forest logging site and M. Senderowicz for help with preparing the illustration. Ivona Kautmanová and D. Szabóová were funded by the Operational Program of Research and Development and co-financed with the European Fund for Regional Development (EFRD). ITMS 26230120004: ‘Building of research and development infrastructure for investigation of genetic biodiversity of organisms and joining IBOL initiative’. Ishika Bera, Aniket Ghosh, Jorinde Nuytinck and Annemieke Verbeken are grateful to the Director, Botanical Survey of India (Kolkata), Head of the Department of Botany & Microbiology & USIC Dept. HNB Garhwal University, Srinagar, Garhwal for providing research facilities. Ishika Bera and Aniket Ghosh acknowledge the staff of the forest department of Arunachal Pradesh for facilitating the macrofungal surveys to the restricted areas. Sergey Volobuev was supported by the Russian Science Foundation (RSF project N 19-77- 00085). Aleksey V. Kachalkin and colleagues were supported by the Russian Science Foundation (grant No. 19-74-10002). The study of Anna M. Glushakova was carried out as part of the Scientific Project of the State Order of the Government of Russian Federation to Lomonosov Moscow State University No. 121040800174-6. Tracey V. Steinrucken and colleagues were supported by AgriFutures Australia (Rural Industries Research and Development Corporation), through funding from the Australian Government Department of Agriculture, Water and the Environment, as part of its Rural Research and Development for Profit program (PRJ-010527). Neven Matočec and colleagues thank the Croatian Science Foundation for their financial support under the project grant HRZZ-IP-2018-01-1736 (ForFungiDNA). Ana Pošta thanks the Croatian Science Foundation for their support under the grant HRZZ-2018-09-7081. The research of Milan Spetik and co-authors was supported by Internal Grant of Mendel University in Brno No. IGAZF/ 2021-SI1003. K.C. Rajeshkumar thanks SERB, the Department of Science and Technology, Government of India for providing financial support under the project CRG/2020/000668 and the Director, Agharkar Research Institute for providing research facilities. Nikhil Ashtekar thanks CSIR-HRDG, INDIA, for financial support under the SRF fellowship (09/670(0090)/2020-EMRI), and acknowledges the support of the DIC Microscopy Facility, established by Dr Karthick Balasubramanian, B&P (Plants) Group, ARI, Pune. The research of Alla Eddine Mahamedi and co-authors was supported by project No. CZ.02.1.01/0.0/0.0/16_017/0002334, Czech Republic. Tereza Tejklová is thanked for providing useful literature. A. Polhorský and colleagues were supported by the Operational Program of Research and Development and co-financed with the European fund for Regional Development (EFRD), ITMS 26230120004: Building of research and development infrastructure for investigation of genetic biodiversity of organisms and joining IBOL initiative. Yu Pei Tan and colleagues thank R. Chen for her technical support. Ernest Lacey thanks the Cooperative Research Centres Projects scheme (CRCPFIVE000119) for its support. Suchada Mongkolsamrit and colleagues were financially supported by the Platform Technology Management Section, National Center for Genetic Engineering and Biotechnology (BIOTEC), Project Grant No. P19-50231. Dilnora Gouliamova and colleagues were supported by a grant from the Bulgarian Science Fund (KP-06-H31/19). The research of Timofey A. Pankratov was supported by the Russian Foundation for Basic Research (grant No. 19-04-00297a). Gabriel Moreno and colleagues wish to express their gratitude to L. Monje and A. Pueblas of the Department of Drawing and Scientific Photography at the University of Alcalá for their help in the digital preparation of the photographs, and to J. Rejos, curator of the AH herbarium, for his assistance with the specimens examined in the present study. Vit Hubka was supported by the Charles University Research Centre program No. 204069. Alena Kubátová was supported by The National Programme on Conservation and Utilization of Microbial Genetic Resources Important for Agriculture (Ministry of Agriculture of the Czech Republic). The Kits van Waveren Foundation (Rijksherbariumfonds Dr E. Kits van Waveren, Leiden, Netherlands) contributed substantially to the costs of sequencing and travelling expenses for M. Noordeloos. The work of B. Dima was supported by the ÚNKP-20-4 New National Excellence Program of the Ministry for Innovation and Technology from the source of the National Research, Development and Innovation Fund, and by the ELTE Thematic Excellence Programme 2020 supported by the National Research, Development and Innovation Office of Hungary (TKP2020-IKA-05). The Norwegian Entoloma studies received funding from the Norwegian Biodiversity Information Centre (NBIC), and the material was partly sequenced through NorBOL. Gunnhild Marthinsen and Katriina Bendiksen (Natural History Museum, University of Oslo, Norway) are acknowledged for performing the main parts of the Entoloma barcoding work. Asunción Morte is grateful to AEI/FEDER, UE (CGL2016-78946-R) and Fundación Séneca - Agencia de Ciencia y Tecnología de la Región de Murcia (20866/PI/18) for financial support. Vladimír Ostrý was supported by the Ministry of Health, Czech Republic - conceptual development of research organization (National Institute of Public Health – NIPH, IN 75010330). Konstanze Bensch (Westerdijk Fungal Biodiversity Institute, Utrecht) is thanked for correcting the spelling of various Latin epithets.

Desert truffles are hypogeous edible fungi that have been exclusively harvested in wild areas for hundreds of years. Land-use changes coupled with shifts in precipitation pattern and volume, as a result of climate change, have led to a decline in wild production of these fungi. Due to their high nutritional value, as well as rising market prices, efforts were stepped toward domestication more than 20 years ago. The present chapter describes the achievements made to understand the biology and diversity of these desert truffles which have helped to make this resource more sustainable. Most efforts to domesticate this natural resource have begun primarily with Terfezia claveryi Chatin. Biotechnological processes for mycorrhizal plant production as well as plantation management practices are analyzed with the experience accumulated to date. Terfezia cultivation is a totally organic crop, with minimum water irrigation, without the consumption of fertilizers or phytosanitary products and using native fungal and plant species. Thus, the longstanding tradition of desert truffle harvesting looks to the future, by adapting its domestication to modern agriculture.

Novel species of fungi described in this study include those from various countries as follows: Australia, Austroboletus asper on soil, Cylindromonium alloxyli on leaves of Alloxylon pinnatum, Davidhawksworthia quintiniae on leaves of Quintinia sieberi, Exophiala prostantherae on leaves of Prostanthera sp., Lactifluus lactiglaucus on soil, Linteromyces quintiniae (incl. Linteromyces gen. nov.) on leaves of Quintinia sieberi, Lophotrichus medusoides from stem tissue of Citrus garrawayi, Mycena pulchra on soil, Neocalonectria tristaniopsidis (incl. Neocalonectria gen. nov.) and Xyladictyochaeta tristaniopsidis on leaves of Tristaniopsis collina, Parasarocladium tasmanniae on leaves of Tasmannia insipida, Phytophthora aquae-cooljarloo from pond water, Serendipita whamiae as endophyte from roots of Eriochilus cucullatus, Veloboletus limbatus (incl. Veloboletus gen. nov.) on soil. Austria, Cortinarius glaucoelotus on soil. Bulgaria, Suhomyces rilaensis from the gut of Bolitophagus interruptus found on a Polyporus sp. Canada, Cantharellus betularum among leaf litter of Betula, Penicillium saanichii from house dust. Chile, Circinella lampensis on soil, Exophiala embothrii from rhizosphere of Embothrium coccineum. China, Colletotrichum cycadis on leaves of Cycas revoluta. Croatia, Phialocephala melitaea on fallen branch of Pinus halepensis. Czech Republic, Geoglossum jirinae on soil, Pyrenochaetopsis rajhradensis from dead wood of Buxus sempervirens. Dominican Republic, Amanita domingensis on litter of deciduous wood, Melanoleuca dominicana on forest litter. France, Crinipellis nigrolamellata (Martinique) on leaves of Pisonia fragrans, Talaromyces pulveris from bore dust of Xestobium rufovillosum infesting floorboards. French Guiana, Hypoxylon hepaticolor on dead corticated branch. Great Britain, Inocybe ionolepis on soil. India, Cortinarius indopurpurascens among leaf litter of Quercus leucotrichophora. Iran, Pseudopyricularia javanii on infected leaves of Cyperus sp., Xenomonodictys iranica (incl. Xenomonodictys gen. nov.) on wood of Fagus orientalis. Italy, Penicillium vallebormidaense from compost. Namibia, Alternaria mirabibensis on plant litter, Curvularia moringae and Moringomyces phantasmae (incl. Moringomyces gen. nov.) on leaves and flowers of Moringa ovalifolia, Gobabebomyces vachelliae (incl. Gobabebomyces gen. nov.) on leaves of Vachellia erioloba, Preussia procaviae on dung of Procavia capensis. Pakistan, Russula shawarensis from soil on forest floor. Russia, Cyberlindnera dauci from Daucus carota. South Africa, Acremonium behniae on leaves of Behnia reticulata, Dothiora aloidendri and Hantamomyces aloidendri (incl. Hantamomyces gen. nov.) on leaves of Aloidendron dichotomum, Endoconidioma euphorbiae on leaves of Euphorbia mauritanica, Eucasphaeria proteae on leaves of Protea neriifolia, Exophiala mali from inner fruit tissue of Malus sp., Graminopassalora geissorhizae on leaves of Geissorhiza splendidissima, Neocamarosporium leipoldtiae on leaves of Leipoldtia schultzii, Neocladosporium osteospermi on leaf spots of Osteospermum moniliferum, Neometulocladosporiella seifertii on leaves of Combretum caffrum, Paramyrothecium pituitipietianum on stems of Grielum humifusum, Phytopythium paucipapillatum from roots of Vitis sp., Stemphylium carpobroti and Verrucocladosporium carpobroti on leaves of Carpobrotus quadrifolius, Suttonomyces cephalophylli on leaves of Cephalophyllum pilansii. Sweden, Coprinopsis rubra on cow dung, Elaphomyces nemoreus from deciduous woodlands. Spain, Polyscytalum pini-canariensis on needles of Pinus canariensis, Pseudosubramaniomyces septatus from stream sediment, Tuber lusitanicum on soil under Quercus suber. Thailand, Tolypocladium flavonigrum on Elaphomyces sp. USA, Chaetothyrina spondiadis on fruits of Spondias mombin, Gymnascella minnisii from bat guano, Juncomyces patwiniorum on culms of Juncus effusus, Moelleriella puertoricoensis on scale insect, Neodothiora populina (incl. Neodothiora gen. nov.) on stem cankers of Populus tremuloides, Pseudogymnoascus palmeri from cave sediment. Vietnam, Cyphellophora vietnamensis on leaf litter, Tylopilus subotsuensis on soil in montane evergreen broadleaf forest. Morphological and culture characteristics are supported by DNA barcodes.

Predicted increases in atmospheric concentration of carbon dioxide (CO

A review of the results obtained so far on the biology of desert truffles, and especially in the symbiosis between Helianthemum almeriense and Terfezia claveryi, is presented with the aim of making a socio-economic use of this natural resource from the southeast of Spain and the Mediterranean Basin. The mycorrhizal morphology between different species of the Helianthemum genus with T. claveryi has been characterized as an ectendomycorrhiza continuum, where the presence of intercellular and intracellular hyphae is always found along the same root. The obstacles found in the production of mycorrhized plants are analysed, and the solutions by using photoautotrophic micropropagation systems, optimization of mycelial culture conditions or the use of plant growth-promoting bacteria (PGPR) are exposed. In addition, the physiological and molecular mechanisms, which regulate the tolerance of this symbiosis to water stress, are discussed through the role of plant and/or fungal aquaporins. Finally, the latest advances in the cultivation and mycosilviculture of T. claveryi are commented.

International audience; AbstractDesert truffles have become an alternative agricultural crop in semiarid areas of the Iberian Peninsula due to their much appreciated edible value and their low water requirements for cultivation. Although most studies related to desert truffle production point to the sole importance of precipitation, this work is the first systematic study carried out to characterize whether other important agroclimatic parameters, for example reference evapotranspiration, soil water potential, relative air humidity %, aridity index or air vapour pressure deficit, may have an impact on a desert truffle production in an orchard with mycorrhizal plants of Helianthemum almeriense × Terfezia claveryi for 15 years from the plantation. The results show for the first time that T. claveryi production has two key periods, during its annual cycle: autumn (September to October) and spring (end of March). The aridity index and soil water potential seem to be the most manageable parameters in the field and can be easily controlled by applying irrigation during the abovementioned periods. Agroclimatic parameters can influence the final crop a long time before the desert truffle fruiting season contrary to what happens with other edible mycorrhizal mushrooms. Four different models to manage desert truffle plantations are proposed based on these agroclimatic parameters in order to optimize and stabilize carpophore fructifications over the years.

Las nuevas especies de hongos descritas en este estudio incluyen las de varios países de la siguiente manera: Antártida, Apenidiella antarctica de permafrost, Cladosporium fildesense de una esponja marina no identificada. Argentina, Geastrum wrightii sobre humus en bosque mixto. Australia, Golovinomyces glandulariae en Glandularia aristigera, Neoanungitea eucalyptorum en hojas de Eucalyptus grandis, Teratosphaeria corymbiicola en hojas de Corymbia ficifolia, Xylaria eucalypti en hojas de Eucalyptus radiata. Brasil, Bovista psammophila en suelo, Fusarium awaxy en tallos podridos de Zea mays, Geastrum lanuginosum en suelo cubierto de hojarasca, Hermetothecium mikaniae-micranthae (incl. Hermetothecium gen. Nov.) En Mikania micrantha, Penicillium reconvexovelosoi en suelo, Stagonoscciiops de podnacciiopsis de glicina máx. Islas Vírgenes Británicas, Lactifluus guanensis en suelo., Novel species of fungi described in this study include those from various countries as follows: Antarctica , Apenidiella antarctica from permafrost, Cladosporium fildesense from an unidentified marine sponge. Argentina , Geastrum wrightii on humus in mixed forest. Australia , Golovinomyces glandulariae on Glandularia aristigera, Neoanungitea eucalyptorum on leaves of Eucalyptus grandis, Teratosphaeria corymbiicola on leaves of Corymbia ficifolia, Xylaria eucalypti on leaves of Eucalyptus radiata. Brazil , Bovista psammophila on soil, Fusarium awaxy on rotten stalks of Zea mays, Geastrum lanuginosum on leaf litter covered soil, Hermetothecium mikaniae-micranthae (incl. Hermetothecium gen. nov.)on Mikania micrantha, Penicillium reconvexovelosoi in soil, Stagonosporopsis vannaccii from pod of Glycine max. British Virgin Isles, Lactifluus guanensis on soil. Canada , Sorocybe oblongispora on resin of Picea rubens. Chile , Colletotrichum roseum on leaves of Lapageria rosea. China, Setophoma caverna from carbonatite in Karst cave. Colombia , Lareunionomyces eucalypticola on leaves of Eucalyptus grandis. Costa Rica , Psathyrella pivae on wood. Cyprus, Clavulina iris on calcareous substrate. France, Chromosera ambigua and Clavulina iris var. occidentalis on soil. French West Indies, Helminthosphaeria hispidissima on dead wood. Guatemala , Talaromyces guatemalensis in soil. Malaysia, Neotracylla pini (incl. Tracyllales ord. nov. and Neotra- cylla gen. nov.)and Vermiculariopsiella pini on needles of Pinus tecunumanii. New Zealand , Neoconiothyrium viticola on stems of Vitis vinifera, Parafenestella pittospori on Pittosporum tenuifolium, Pilidium novae-zelandiae on Phoenix sp. Pakistan , Russula quercus-floribundae on forest floor. Portugal, Trichoderma aestuarinum from saline water. Russia, Pluteus liliputianus on fallen branch of deciduous tree, Pluteus spurius on decaying deciduous wood or soil. South Africa, Alloconiothyrium encephalarti, Phyllosticta encephalarticola and Neothyrostroma encephalarti (incl. Neothyrostroma gen. nov.)on leaves of Encephalartos sp., Chalara eucalypticola on leaf spots of Eucalyptus grandis × urophylla, Clypeosphaeria oleae on leaves of Olea capensis, Cylindrocladiella postalofficium on leaf litter of Sideroxylon inerme, Cylindromonium eugeniicola (incl. Cylindromonium gen. nov.)on leaf litter of Eugenia capensis, Cyphellophora goniomatis on leaves of Gonioma kamassi, Nothodactylaria nephrolepidis (incl. Nothodactylaria gen. nov. and Nothodactylariaceae fam. nov.)on leaves of Nephrolepis exaltata , Falcocladium eucalypti and Gyrothrix eucalypti on leaves of Eucalyptus sp., Gyrothrix oleae on leaves of Olea capensis subsp. macrocarpa, Harzia metrosideri on leaf litter of Metrosideros sp., Hippopotamyces phragmitis (incl. Hippopota-myces gen. nov.)on leaves of Phragmites australis, Lectera philenopterae on Philenoptera violacea , Leptosillia mayteni on leaves of Maytenus heterophylla , Lithohypha aloicola and Neoplatysporoides aloes on leaves of Aloe sp., Millesimomyces rhoicissi (incl. Millesimomyces gen. nov.) on leaves of Rhoicissus digitata, Neodevriesia strelitziicola on leaf litter of Strelitzia nicolai, Neokirramyces syzygii (incl. Neokirramyces gen. nov.)on leaf spots of Syzygium sp., Nothoramichloridium perseae (incl. Nothoramichloridium gen.nov.and Anungitiomycetaceae fam. nov.)on leaves of Persea americana, Paramycosphaerella watsoniae on leaf spots of Watsonia sp., Penicillium cuddlyae from dog food, Podocarpomyces knysnanus (incl. Podocarpomyces, gen.nov.)on leaves of Podocarpus falcatus, Pseudocercospora heteropyxidicola on leaf spots of Heteropyxis natalensis, Pseudopenidiella podocarpi, Scolecobasidium podocarpi and Ceramothyrium podocarpicola on leaves of Podocarpus latifolius, Scolecobasidium blechni on leaves of Blechnum capense, Stomiopeltis syzygii on leaves of Syzygium chordatum, Strelitziomyces knysnanus (incl. Strelitziomyces gen.nov.)on leaves of Strelitzia alba, Talaromyces clemensii from rotting wood in goldmine, Verrucocladosporium visseri on Carpobrotus edulis. Spain, Boletopsis mediterraneensis on soil, Calycina cortegadensisi on a living twig of Castanea sativa, Emmonsiellopsis tuberculata in fluvial sediments, Mollisia cor-tegadensis on dead attached twig of Quercus robur, Psathyrella ovispora on soil, Pseudobeltrania lauri on leaf litter of Laurus azorica, Terfezia dunensis in soil, Tuber lucentum in soil, Venturia submersa on submerged plant debris. Thailand,/b>, Cordyceps jakajanicola on cicada nymph, Cordyceps kuiburiensis on spider, Distoseptispora caricis on leaves of Carex sp., Ophiocordyceps khonkaenensis on cicada nymph. USA, Cytosporella juncicola and Davidiello- myces juncicola on culms of Juncus effusus, Monochaetia massachusettsianum from air sample, Neohelicomyces melaleucae and Periconia neobrittanica on leaves of Melaleuca styphelioides ?? lanceolata, Pseudocamarosporium eucalypti on leaves of Eucalyptus sp., Pseudogymnoascus lindneri from sediment in a mine, Pseudogymnoascus turneri from sediment in a railroad tunnel, Pulchroboletus sclerotiorum on soil, Zygosporium pseudomasonii on leaf of Serenoa repens. Vietnam, Boletus candidissimus and Veloporphyrellus vulpinus on soil.Morphological and culture characteristics are supported by DNA barcodes.

Sixty-four native bacterial colonies were isolated from mycorrhizal roots of Helianthemum almeriense colonized by Terfezia claveryi, mycorrhizosphere soil, and peridium of T. claveryi to evaluate their effect on mycorrhizal plant production. Based on the phylogenetic analysis of the 16S rDNA partial sequence, 45 different strains from 17 genera were gathered. The largest genera were Pseudomonas (40.8 % of the isolated strains), Bacillus (12.2 % of isolated strains), and Varivorax (8.2 % of isolated strains). All the bacteria were characterized phenotypically and by their plant growth-promoting rhizobacteria (PGPR) traits (auxin and siderophore production, phosphate solubilization, and ACC deaminase activity). Only bacterial combinations with several PGPR traits or Pseudomonas sp. strain 5, which presents three different PGPR traits, had a positive effect on plant survival and growth. Particularly relevant were the bacterial treatments involving auxin release, which significantly increased the root-shoot ratio and mycorrhizal colonization. Moreover, Pseudomonas mandelii strain 29 was able to considerably increase mycorrhizal colonization but not plant growth, and could be considered as mycorrhiza-helper bacteria. Therefore, the mycorrhizal roots, mycorrhizosphere soil, and peridium of desert truffles are environments enriched in bacteria which may be used to increase the survival and mycorrhization in the desert truffle plant production system at a semi-industrial scale.

Terfezia claveryi Chatin was the first desert truffle species to be cultivated, the mycorrhizal plants being successfully produced by using both desert truffle spores and mycelia. However, it is more advisable to use mycelium than spores whenever possible and profitable. Given the low yields of mycelia obtained using traditional culture methods of this truffle, the medium composition was modified in an attempt to determine its nutritional requirements. For this, an assay involving response surface methodology was performed using Box-Behnken design to find the optimal parameters for the high production of mycelial biomass. The best results were obtained with glucose as carbon source, buffering the pH at 5 during culture, adding a pool of vitamins, and adjusting the optimal concentrations of carbon and nitrogen sources of the MMN medium. Biomass production increased from 0.3 to 3 g L−1 dry weight and productivity increased from 10.7 to 95.8 mg L−1 day−1 dry weight. The produced mycelium was able to colonize Helianthemum roots efficiently, providing more than 50% ectomycorrhizal colonization.

The development of ectomycorrhizal associations is crucial for growth of many forest trees. However, the signals that are exchanged between the fungus and the host plant during the colonization process are still poorly understood. In this study, we have identified the relationship between expression patterns of Laccaria bicolor aquaporin LbAQP1 and the development of ectomycorrhizal structures in trembling aspen (Populus tremuloides) seedlings. The peak expression of LbAQP1 was 700-fold higher in the hyphae within the root than in the free-living mycelium after 24 h of direct interaction with the roots. Moreover, in LbAQP1 knock-down strains, a non-mycorrhizal phenotype was developed without the Hartig net and the expression of the mycorrhizal effector protein MiSSP7 quickly declined after an initial peak on day 5 of interaction of the fungal hyphae with the roots. The increase in the expression of LbAQP1 required a direct contact of the fungus with the root and it modulated the expression of MiSSP7. We have also determined that LbAQP1 facilitated NO, H2 O2 and CO2 transport when heterologously expressed in yeast. The report demonstrates that the L. bicolor aquaporin LbAQP1 acts as a molecular signalling channel, which is fundamental for the development of Hartig net in root tips of P. tremuloides.

Sporocarp formation is part of the reproductive stage in the life cycle of many mycorrhizal macrofungi. Sporocarp formation is accompanied by a transcriptomic switch and profound changes in regulation of the gene families that play crucial roles in the sporocarp initiation and maturation. Since sporocarp growth requires efficient water delivery, in the present study, we investigated changes in transcript abundance of six fungal aquaporin genes that could be cloned from the ectomycorrhizal fungus Laccaria bicolor strain UAMH8232, during the initiation and development of its basidiocarp. Aquaporins are intrinsic membrane proteins facilitating the transmembrane transport of water and other small neutral molecules. In controlled-environment experiments, we induced basidiocarp formation in L. bicolor, which formed ectomycorrhizal associations with white spruce (Picea glauca) seedlings. We profiled transcript abundance corresponding to six fungal aquaporin genes at six different developmental stages of basidiocarp growth and development. We also compared physiological parameters of non-inoculated to mycorrhizal seedlings with and without the presence of basidiocarps. Two L. bicolor aquaporins--JQ585592, a functional channel for CO2, NO and H2O2, and JQ585595, a functional water channel--showed the greatest degree of upregulation during development of the basidiocarp. Our findings point to the importance of aquaporin-mediated transmembrane water and CO2 transport during distinct stages of basidiocarp development.

This chapter summarizes the latest basic and applied advances in desert truffle research carried out to improve our knowledge of the biodiversity, physiology, biotechnology, and cultivation of these hypogeous and edible fungi. ITS-rDNA sequences in phylo-geographic studies and host plant and soil pH characteristics have been the key to describing eight new desert truffle species. The production of desert truffle mycorrhizal plants has been improved by using β-cyclodextrin and bioreactors for mycelium culture and native beneficial bacteria (PGPR and MHB) to increase seedling survival and mycorrhization. Some fungal enzymes have also been characterized in Terfezia claveryi ascocarps. The presence of alkaline phosphatase both in mycelia and ascocarps indicates that this enzyme plays an important role during the life cycle of T. claveryi, while acid phosphatase might be involved in a process that takes place during the ascocarp stage. Numerous desert truffle plantations have been established in Spain in the last 10 years. A high density of mycorrhizal plants combined with a proper irrigation are two important factors to stimulate ascocarp production. The combination of a high rate of intracellular colonization together with the fine-tuned expression of fungal and plant aquaporins could result in a morpho-physiological adaptation of this symbiosis in drought conditions. Moreover, desert truffle sylviculture is proposed for improving truffle production and for conserving the natural areas where desert truffle grow.

Changes in root and leaf hydraulic properties and stimulation of transpiration rates that were initially triggered by defoliation were accompanied by corresponding changes in leaf and root aquaporin expression. Aspen (Populus tremuloides) seedlings were subjected to defoliation treatments by removing 50, 75 % or all of the leaves. Root hydraulic conductivity (Lpr) was sharply reduced in plants defoliated for 1 day and 1 week. The decrease in L pr could not be prevented by stem girdling and it was accompanied in one-day-defoliated plants by a large decrease in the root expression of PIP1,2 aquaporin and an over twofold decrease in hydraulic conductivity of root cortical cells (L pc). Contrary to L pr and L pc, 50 and 75 % defoliation treatments profoundly increased leaf lamina conductance (K lam) after 1 day and this increase was similar in magnitude for both defoliation treatments. Transpiration rates (E) rapidly declined after the removal of 75 % of leaves. However, E increased by over twofold in defoliated plants after 1 day and the increases in E and K lam were accompanied by five- and tenfold increases in the leaf expression of PIP2;4 in 50 and 75 % defoliation treatments, respectively. Defoliation treatments also stimulated net photosynthesis after 1 day and 3 weeks, although the increase was not as high as E. Leaf water potentials remained relatively stable following defoliation with the exception of a small decrease 1 day after defoliation which suggests that root water transport did not initially keep pace with the increased transpirational water loss. The results demonstrate the importance of root and leaf hydraulic properties in plant responses to defoliation and point to the involvement of PIP aquaporins in the early events following the loss of leaves.

The influence of inorganic and organic phosphorus (P) and the absence of P in the culture medium on the type of mycorrhizal colonization formed (ecto-, ectendo-, or endomycorrhiza) during Helianthemum almeriense x Terfezia claveryi symbiosis in in vitro conditions was analyzed. This is the first time that the relative proportions of the different mycorrhizal types in mycorrhizal roots of H. almeriense have been quantified and statistically analyzed. The relative proportions of the mycorrhizal types depended on the P source in the medium, suggesting that it is the organic P form that induces the formation of intracellular colonization. The above association should be considered as a continuum between intra- and intercellular colonizations, the most appropriate term for defining it being ectendomycorrhiza. The influence of the endogenous concentration of P on plant growth was also analyzed. P translocation was observed from shoot to roots, especially in mycorrhizal plants because mycorrhizal roots showed higher growth than non-mycorrhizal roots and/or because of an extra P demand from mycelium inside the roots. Soluble and cell wall acid phosphatases activities from H. almeriense roots were kinetically characterized at optimum pH (5.0), using p-nitrophenyl phosphate as substrate, with K m values of 3.4 and 1.8 mM, respectively. Moreover, the plant acid phosphatase and fungal alkaline phosphatases activities were histochemically localised in mycorrhizal H. almeriense roots by fluorescence with enzyme-labelled fluorescence substrate.

Physiological parameters of mycorrhizal symbiosis by Helianthemum almeriense and Terfezia claveryi in orchards were characterized under water deficit conditions. Our orchard included 40 mycorrhizal and 40 nonmycorrhizal plants. Only mycorrhizal plants survived at the beginning of the experimental period, indicating dependency on fungal symbionts in roots for survival. Drought stress significantly affected the mycorrhizal colonization percentage which was 70% in nonirrigated mycorrhizal and 48% in irrigated mycorrhizal plants. No significant differences in plant growth were observed between nonirrigated and irrigated mycorrhizal plants before and after drought stress. Stomatal conductance was more sensitive to water stress than shoot water potential. It decreased more than two-fold under drought-stress compared to control mycorrhizal plants under irrigation/light saturating conditions, indicating important stomatal closure with water deficit. Plants’ water use efficiency improved with drought with stomatal conductance values below 0.3 mol m−2 s−1. The ability to maintain open stomata and photosynthesis under drought increased carbon supply for growth, and ascocarp fruiting which requires current photosynthates. Basically, H. almeriense shows a conservative water use strategy based mainly on avoiding drought stress by reducing stomatal conductance as soil water potential decreases and atmospheric conditions dry. The results show that mycorrhizal H. almeriense plants maintain good physiological parameters with low soil matric potentials, thus making them an alternative agricultural crop in arid/semi-arid areas.

The ability of two species of desert truffle, Terfezia claveryi strain TcS2 and Picoa lefebvrei strain OL2, to tolerate water stress in pure culture has been investigated. Both T. claveryi and P. lefebvrei strains exhibited a mycelium growth pattern characteristic of drought tolerant species. However, they were only tolerant to moderate water stress, below -1.07 MPa, with the P. lefebvrei isolate being slightly more drought tolerant than the T. claveryi isolate. The increased alkaline phosphatase (ALP) activity observed in both fungi at moderate water stress with respect to the control indicated the functional adaptation of these mycelia to these drought conditions. ALP activity can be used as an indicator of the metabolic activity of these fungi. Slight water stress (-0.45 MPa) could improve mycelial inoculum production of these desert truffles. Moreover, P. lefebvrei could be a good candidate for further desert truffle mycorrhizal plant cultivation programmes in semiarid Mediterranean areas.

The development of ectomycorrhizal associations is crucial for growth of many forest trees. However, the signals that are exchanged between the fungus and the host plant during the colonization process are still poorly understood. In this study, we have identified the relationship between expression patterns of Laccaria bicolor aquaporin LbAQP1 and the development of ectomycorrhizal structures in trembling aspen (Populus tremuloides) seedlings. The peak expression of LbAQP1 was 700-fold higher in the hyphae within the root than in the free-living mycelium after 24 h of direct interaction with the roots. Moreover, in LbAQP1 knock-down strains, a non-mycorrhizal phenotype was developed without the Hartig net and the expression of the mycorrhizal effector protein MiSSP7 quickly declined after an initial peak on day 5 of interaction of the fungal hyphae with the roots. The increase in the expression of LbAQP1 required a direct contact of the fungus with the root and it modulated the expression of MiSSP7. We have also determined that LbAQP1 facilitated NO, H2 O2 and CO2 transport when heterologously expressed in yeast. The report demonstrates that the L. bicolor aquaporin LbAQP1 acts as a molecular signalling channel, which is fundamental for the development of Hartig net in root tips of P. tremuloides.

The following types of mycorrhizas are distinguished: Ectomycorrhizas, which are characterized by a Hartig net and may or may not have a mantle Endomycorrhizas, which have no Hartig net and may or may not have a mantle but are characterized by undifferentiated coil-shaped intracellular hyphae Ectendomycorrhizas, which display a Hartig net with or without a mantle alongside various forms of intracellular coiled or spherical hyphae

We have performed the isolation, functional characterization, and expression analysis of aquaporins in roots and leaves of Helianthemum almeriense, in order to evaluate their roles in tolerance to water deficit. Five cDNAs, named HaPIP1;1, HaPIP1;2, HaPIP2;1, HaPIP2;2, and HaTIP1;1, were isolated from H. almeriense. A phylogenetic analysis of deduced proteins confirmed that they belong to the water channel proteins family. The HaPIP1;1, HaPIP2;1, and HaTIP1;1 genes encode functional water channel proteins, as indicated by expression assays in Saccharomyces cerevisiae, showing divergent roles in the transport of water, CO2, and NH3. The expression patterns of the genes isolated from H. almeriense and of a previously described gene from Terfezia claveryi (TcAQP1) were analyzed in mycorrhizal and nonmycorrhizal plants cultivated under well-watered or drought-stress conditions. Some of the studied aquaporins were subjected to fine-tuned expression only under drought-stress conditions. A beneficial effect on plant physiological parameters was observed in mycorrhizal plants with respect to nonmycorrhizal ones. Moreover, stress induced a change in the mycorrhizal type formed, which was more intracellular under drought stress. The combination of a high intracellular colonization, together with the fine-tuned expression of aquaporins could result in a morphophysiological adaptation of this symbiosis to drought conditions.

Since the first plantation of Terfezia mycorrhizal plants was established in 1999 in Murcia (Spain), an increasing demand for this crop, not only in Spain but also in other countries, has prompted research into new strategies and aspects that will enable us to pass from the experimental scale to medium- to large-scale cultivation. As a consequence of this leap, a new photoautotrophic Helianthemum micropropagation system has been developed. This system reduces the time needed to obtain mycorrhizal plants to 3 months since fungal inoculation is carried out at the moment plants are transferred from in vitro to ex vitro conditions, so that plant acclimatization and mycorrhization occur at the same time.

In the present paper, we confirmed that alkaline phosphatase (ALP) is the main phosphatase present in ascocarps of the edible mycorrhizal fungus Terfezia claveryi. The enzyme was partially purified by precipitation with polyethylene glycol. The purification achieved from a crude extract was fivefold, with 53% of the activity recovered, and acid phosphatase, most of the lipids and phenolic compounds were eliminated. Alkaline phosphatase was kinetically characterised at pH 10.0, the optimum for this enzyme, using p-nitrophenyl phosphate as substrate. The V(max) and K(m) values were 0.3 micromol.min(-1).mg(-1) protein and 9.0 mM, respectively. Orthovanadate was a competitive inhibitor of ALP, with a K(i) of 42.5 microM. The enzyme was histochemically localised in the peridium, the hypothecium and in the ascogenic hyphae of the gleba using both colour and fluorescent reactions. The results presented suggest that the ascocarp of T. claveryi, at some stages of its development, may become nutritionally autonomous and independent of the host plant.

Terfezia claveryi Chatin es un hongo hipogeo comestible perteneciente al grupo conocido como “trufas del desierto”, localizado principalmente en ecosistemas áridos y semiáridos de la cuenca del Mediterráneo. En su hábitat natural, T. claveryi establece simbiosis ectendomicorrícica con numerosas especies del género Helianthemum y su fructificación es en primavera. Fue la primera especie dentro de las trufas del desierto en ser cultivada, y desde entonces se ha convertido en un cultivo agrícola alternativo en zonas semiáridas de la Península Ibérica, que ha ido incrementándose durante los últimos años. Esta tesis tiene como objetivo principal el estudio del comportamiento miceliar de la trufa del desierto T. claveryi, tanto en laboratorio como en campo, así como los microorganismos asociados a la rizosfera de plantas hospedantes del género Helianthemum con el fin de conocer más su biología y mejorar su cultivo. Para ello, se planteó el desarrollo de cinco objetivos parciales que dieron lugar a los siguientes resultados y conclusiones. Inicialmente, se evaluó el crecimiento miceliar de T. claveryi en condiciones in vitro, probando en el medio de cultivo MMN (sólido y líquido) distintas concentraciones de macronutrientes, micronutrientes y vitaminas, diferentes condiciones de pH, tamaño de inóculo inicial y relación C/N. Los resultados permitieron diseñar un medio de cultivo MMN optimizado que mejoraba la biomasa miceliar producida. Además, el micelio producido en cultivo líquido en biorreactor permitió la producción de planta micorrizada. En segundo lugar, se estudió la dinámica miceliar de T. claveryi s.l. en suelo durante 4 años en distintas zonas naturales y en plantaciones de la Región de Murcia. Para ello, se diseñaron cebadores específicos para la cuantificación de ADN en suelo con la técnica de PCR cuantitativa a tiempo real, en cada una de las estaciones. Finalmente, se desarrolló un protocolo con la pareja de primers Tc452F/TerclaR, que detecta los productos de PCR. La distribución del micelio fue independiente de las características geográficas de las áreas estudiadas. El año fue la única variable que separó significativamente los datos de micelio en dos grupos (años 1-4 y 2-3), existiendo diferencias significativas sólo para las estaciones de invierno y primavera. Además, el micelio de invierno se correlacionó fuertemente con las variables agroclimáticas del otoño previo, siendo positivas para la precipitación, el índice de aridez y la humedad relativa y negativas para la temperatura máxima, el déficit de presión de vapor y la evapotranspiración. En tercer lugar, se aislaron las bacterias de la rizosfera de T. claveryi x H. almeriense a lo largo de las estaciones. Se realizó una caracterizaron fenotípica, bioquímica, molecular y de las actividades PGPR de las colonias bacterianas (solubilización del fósforo, liberación de auxinas, producción de sideróforos y actividad ACC-deaminasa). Los análisis estadísticos revelaron un enriquecimiento significativo en bacterias solubilizadoras de fósforo (liberadoras de ácidos orgánicos) y con actividad ACC-deaminasa durante la época de fructificación del hongo. Además, se confirmó que un cambio del estado fenológico de la planta determinaba un cambio en la comunidad bacteriana vinculado a sus rasgos PGPR. Por último, para conocer la comunidad de hongos asociados a plantas productoras de ascocarpos frente a las plantas no productoras se utilizaron herramientas de secuenciación masiva de ADN, tanto en suelo como en raíz. Se encontraron distintos patrones en la composición de especies de hongos en función de la productividad. Además, algunos modos tróficos fúngicos fueron identificados como relevantes por tener un efecto positivo o negativo sobre la producción de ascocarpos. Finalmente, se encontraron un grupo de OTUs significativos asociados a zonas productivas, que podrían usarse como marcadores para la localización de trufas del desierto. Terfezia claveryi Chatin is an edible hypogeous fungus belonging to the group known as "desert truffles", mainly found in arid and semi-arid ecosystems of the Mediterranean basin. In its natural habitat, T. claveryi establishes ectendomycorrhizal symbiosis with several species of the genus Helianthemum and its fruiting is in spring. Moreover, it is the first species of desert truffle to be cultivated and has become an alternative agricultural crop in semi-arid areas of the Iberian Peninsula, which has been increasing in recent years. The main objective of this thesis is to study the mycelial behaviour of the desert truffle T. claveryi, both in the laboratory and in the field, as well as the microorganisms associated with the rhizosphere of host plants of the genus Helianthemum. To this end, five partial objectives were developed, which led to the following results and conclusions. First, the mycelial growth of T. claveryi was evaluated under in vitro conditions by testing the MMN culture medium (solid and liquid) with different concentrations of macronutrients, micronutrients and vitamins, and under different conditions of pH, initial inoculum size and C/N ratio. The results yielded an optimised MMN culture medium that improved the mycelial biomass produced. In addition, the mycelium produced in liquid culture in bioreactor was used for inoculation and production of desert truffle mycorrhizal plants. Secondly, the seasonal dynamics of T. claveryi s.l. mycelium was studied in soil during 4 years in different natural areas and in plantations in the Region of Murcia. For this purpose, specific primers were designed for DNA quantification using real-time PCR in each of the seasons. SYBR-Green based qPCR protocol was developed with the primer pair Tc452F/TerclaR as a suitable candidate to detect the specific target. Mycelial distribution in different soils was independent of the geographical features of the experimental site. The analysis revealed that year as the only factor that significantly separated the mycelial data into two groups (years 1-4 and 2-3), where significant differences were only found for the winter and spring seasons. Moreover, winter mycelium was strongly correlated with agroclimatic variables in autumn season, in which precipitation, aridity index and relative humidity were positive and maximum temperature, vapor pressure deficit and evapotranspiration were negative correlated. Thirdly, bacteria were isolated from the rhizosphere of T. claveryi x H. almeriense across seasons, or from the different stages of host plant phenology. Phenotypic, biochemical, molecular and PGPR activities of the bacterial colonies (phosphorus solubilisation, auxin release, siderophore production and ACC-deaminase activity) were characterized. Statistical analyses revealed that there was a significant enrichment in phosphorus solubilising bacteria (organic acid releasing) and bacteria with ACC-deaminase activity during the fruiting season of the fungus (spring). Moreover, it was also confirmed that a change in the phenological state of the plant determined a change in the bacterial community linked to its PGPR traits. Finally, to understand the fungal community associated with ascocarp productive plants versus non-productive plants, large-scale sequencing tools for DNA were used to perform a metagenomics assay, both in soil and root. Different patterns in fungal species composition were found by productivity. In addition, some trophic modes of the fungal species obtained were identified as relevant for having a positive or negative effect on ascocarp productivity in plantation. Furthermore, a group of significant OTUs associated with productive areas were found, which could be used as markers for the localization of desert truffles.