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Researchers are exploring plant-based protein sources to address both malnutrition and climate change. Desert truffles are rich in protein (i.e., ≈20%) and offer a cheaper and more environmentally friendly option. However, desert truffle cultivation is limited by environmental factors like rainfall and soil properties. This study was conducted to understand the soil conditions and microbiomes associated with desert truffles growing in parts of Saudi Arabia. Based on yield, the truffle fields were categorized into high-yield (≈50 kg/ha annually) and low-yield (≈2 kg/ha annually) truffle farms. Truffle yield differences were not significantly influenced by most soil physicochemical variables except for total nitrogen (negatively correlated). However, low soil nitrogen alone did not explain yield disparities, as wild truffle fields with low nitrogen also produced fewer truffles. In contrast, truffle yield showed a strong positive correlation with calcium carbonate content. We hypothesized that the unmeasured irrigation schedule was most likely behind the truffle yield differences especially during fruiting season. Furthermore, the high-yield farms had lower bacteria richness and diversity than the low-yield farms. Environmentally important bacteria genera such as Geodermatophilus and Rubrobacter were found in both farms, although more were found in the low-yield one, whereas more Streptomyces were found in the high-yield farm. In addition, fungal alpha diversity was higher in the high-yield farm with the dominance of Sordariomycetes, Dothideomycetes, Eurotiomycetes, and Glomeromycetes.

Shrubland ecosystems play a crucial role in Mediterranean forests, contributing to soil protection, biodiversity conservation, carbon sequestration, and ecosystem restoration. In semi-arid regions, mycorrhizal woody plants such as Helianthemum spp. form ectendomycorrhizal symbiosis with edible desert truffles, representing an emerging and sustainable crop with significant potential for rural development and economic diversification. Significant progress has been made in the breeding of Terfezia claveryi Chatin, but key aspects of its life cycle, such as the temporal and spatial behaviour of the soil mycelium, remain underexplored. This study aimed to investigate the seasonal dynamics of T. claveryi soil mycelium in plantations and wild areas of the Region of Murcia (Spain) using real-time quantitative PCR. The relationship between fungal biomass and host plant phenology and environmental parameters was also investigated. Our results showed that T. claveryi soil mycelium was higher in plantations than in wild areas, and in Xerolls than in Orthents soils. Fungal dynamics lacked seasonal or annual patterns; however winter mycelium showed a strong correlation with preceding agroclimatic variables, especially precipitation and maximum temperature. This research sheds light on the ecological processes underlying the desert truffle shrublands and offers practical implications for optimising T. claveryi cultivation strategies and promoting ecosystem restoration.

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.

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.

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.

Terfezia boudieri Chatin and Tirmania nivea (Desf.) Trappe, the desert truffles, are mycorrhizal fungi that are mostly endemic to arid and semi-arid areas of the Mediterranean where they are associated with Helianthemum species. The current study aimed to test the use of the two-culture media, Potato Dextrose Agar (PDA) and Malt Extract Agar (MEA), on isolation, apical growth rate (APG) and the production of wet weight of mycelial biomass (WWMBP) of two Moroccan species of Terfezia boudieri and Tirmania nivea collected respectively from Walidia and Boujdour. For the both species PDA and MEA were the most effective culture media for isolation, apical growth rate (APG) and wet weight of mycelial biomass production (WWMBP). This study demonstrated that PDA growth medium outperformed the MEA for both fungal species with an apical growth rate (APG) of (0.05 ± 0.01) cm/h for T. boudieri and T. nivea in PDA, against (0.04 ± 0.00) cm/h for T. boudieri and T. nivea in MEA. Additionally, the wet weight of mycelial biomass production (WWMBP) was measured using the same culture media (PDA) and (MEA). The wet weight of mycelial biomass produced by T. boudieri and T. nivea were nearly identical in PDA medium. The same result was exhibited for T. nivea in MEA. In addition, the T. boudieri and T. nivea species sown in solid media showed a considerable apical growth rate and wet weight of mycelial biomass production (WWMBP). The success of the cultivation process of T. boudieri and T. nivea will enable the potential use of them as ectomycorrhizal inoculum in reforestation programs with their host plant and ultimately the production of edible mushrooms in the field.

Terfezia claveryi Chatin is an obligate ectomycorrhizal hypogeous desert truffle, very rich in active compounds. Our objectives are to promote the hydro-methanolic extract by spectrophotometrically evaluating of bioactive contents and their biological activities. DPPH, ABTS, FRAP and TAC were carried out to estimate the antioxidant potential. The lysis, the anti-hemolytic, the anti-inflammatory and the α-amylase inhibitory properties were investigated. The total phenolic compounds are the majority components 82.27 ± 1.44 (µg GAE/mg extract). Through GC–MS, a total of 06 compounds were identified. The IC 50 value of DPPH and ABTS were respectively (251.03 ± 6,31 µg/mL), (177.64 ± 0.91 µg /mL), and the TAC value was (26.14 ± 0.22 µg AAE /mg extract). The results highlighted a low hemolytic activity 2.37 ± 0.20% at 2 mg/mL and a strong protective effect against AAPH radical-induced hemolysis, HT 50 (min) was 209.56 ± 0.62 (min) compared to the ascorbic acid 224.15 ± 0.65 (min) at 200 µg/mL. Tests conducted revealed a promoting potential to inhibit BSA denaturation, the level of protection at 700 and 1500 (µg/mL) was 69.41% and 83.53%, while diclofenac was 92.16% and 98.43% respectively. Truffles research remain an unexplored field, and this research provides valuable findings. According to the data collected in the current investigation, the hydro-methanolic extract of T. claveryi exhibits in vitro, anti-inflammatory and anti-hemolytic benefits and can be suitable for use in the context of a natural source to protect against inflammation and the side effects linked to oxidative stress. Graphical abstract

Desert truffles are edible hypogeous (forming fruit bodies below ground) fungi that grow in semi-arid and arid areas. They are highly valued for both their culinary and medicinal properties in the Mediterranean basin, the Middle East and the Gulf areas. Desert truffles form mycorrhizae mostly with plants belonging to the Cistaceae family, mainly with Helianthemum species. These truffles are still, usually, collected from the wild, but loss of habitats due to urbanization, desertification, intensive agriculture and global warming, along with an urgent need to develop new crops adapted to arid conditions, are currently hastening efforts towards their domestication. Here, we sum up the successful research leading to cultivation of this crop, based on plots that were established in sandy to silt soils with high pH values and low mineral contents. We report suitable methods for production of mycorrhized seedlings and preferred planting methods. We found that under natural conditions yields are affected by water availability, so irrigation regimes to ensure good yields were sought. Although good yields were indeed obtained in some years, fluctuations in yields over the years were significant; the reasons for this are not entirely clear and are currently under study. This crop is particularly well suited to relatively marginal conditions but prospects for establishment of desert truffles as a niche crop for arid and semi-arid areas depend on further improvements in yields.

Mattirolomyces is an edible commercial sequestrate genus that is globally distributed. From the five described taxa of this genus, Mattirolomyces terfezioides is the most common species in Asia. Our recent attempts to locate M. terfezioides outside its current distribution area in China documented its first records in areas of poplar trees with the lowest known temperature and precipitation averages ever recorded for this species. This peculiar ecology was not reflected on the species-morphological features nor on its phylogenetic position in the genus. The first attempt to apply the phylogenetic network approach to Mattirolomyces revealed its geographic origin in the Asian-Pacific areas prior to frequent long-distance migration events. Based on data from recent study areas, we found that the collections from Inner Mongolia and the Shanxi province were similar to European collections. Asian haplotypes were less distant from the outgroup comparing to collections from Europe, supporting the hypothesis that M. terfezioides was originated from this Chinese area and was subsequently transported to Europe. Exploring M. terfezioides ecology and its mycorrhiza potential to grow in association with poplars would be of great importance for planning cultivation projects of this valuable desert truffle species in Central and Eastern China, a currently underexploited economic sector that deserves further ecological and M. terfezioides mycorrhizal synthesis investigations.

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.