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Kalaharituber pfeilii
Kalaharituber growing on roots of Stipagrostis ciliata var. capensis. Photo by Prof. Joanna Dames, Rhodes University.

Within the framework of the Mycorrhizal Genomics Initiative (MGI) and the 1000 Fungal Genomes (1KFG) projects, we are sequencing a phylogenetically and ecologically diverse suite of mycorrhizal fungi, which include the major clades of symbiotic species associating with plants. Analyses of these genomes will provide insights into the diversity of mechanisms for the mycorrhizal symbiosis, including arbuscular, ericoid-, orchid- and ectomycorrhizal associations.

The Kalahari truffle

The Kalaharituber pfeilii (Pezizaceae) is a desert truffle found in the arid regions of southern Africa, extending from the Northern Cape Province, South Africa into Botswana, Namibia and Angola. The Kalahari truffle (n'abba or sand potato) is an important food for local people as well as a source of income. The truffles grow close to the surface and are tracked by visible cracks formed in the soil by the up-growing hypogeous fruit body. The fruiting season occurs towards the end of the wet season when the weather conditions are favorable.

A number of host plants are suspected to form a mycorrhizal relationship with the Kalahari truffle and have been cited to include watermelon (Citrullus lanatus), Sorghum bicolor, Cynodon dactylon, Eragrostis spp, Grewia flava and Acacia species. This unique truffle is reported to form mycorrhizal association with the vanishing Acacia trees that are important wood-plants for the indigenous people. Recent research at Rhodes University, South Africa investigated the truffle association with Stipagrostis ciliata var. capensis using molecular techniques. Other host plant interactions require further investigation. This truffle is the only one reported to form ectomycorrhizal (ECM) associations with both dicot and monocot plants. It is important to understand this unique characteristic since it represents a juncture between the non-plant specific arbuscular mycorrhizas and the host specific ECMs. Reported changes in the distribution of the truffle could be related to climate change resulting in habitat and vegetation changes as well as increased livestock farming. Understanding the biology of this truffle and their interaction with various host plants are therefore essential.

The truffle shows remarkable tolerance to extreme desert conditions. The genomic data obtained from this fungus, combined with the sequencing data from other desert truffles belonging to the Pezizaceae such as Terfezia boudieri and Terfezia claveryi, will enable us to reveal the mechanisms underlying the remarkable drought resistance of these organisms.

The MGI is a large collaborative effort aiming for master publication(s) describing the evolution of the mycorrhizal symbioses. Researchers who wish to publish analyses using data from unpublished MGI genomes are respectfully required to contact the PIs and JGI to avoid potential conflicts on data use and coordinate other publications with the MGI master paper(s).

Genome Reference(s)