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The commercial value of Terfezia claveryi, an edible desert truffle with important gastronomic, nutritional, and antioxidant properties, has led to growing interest in its cultivation. The erratic and slow growth of T. claveryi mycelium in vitro represents an impairment to obtain mycorrhizal plants, and it makes necessary to find a new culture medium able to overcome these drawbacks. In this work, we analyze the effect of cyclodextrins (CDs) on the growth of T. claveryi mycelium. Different parameters, including colony diameter, growth rate, and colony fresh weight, were evaluated, both in the presence and absence of these encapsulant agents. The results obtained confirm the ability of CDs to stimulate the growth of T. claveryi mycelium when present in the culture medium. A similar effect was observed when CDs were added to the culture medium of Tuber melanosporum. Three natural (α-, β-, and γ) and two modified (hydroxypropil-β and methyl-β) CDs were assayed. The best results were obtained with β-cyclodextrin, but no improvement was observed with its chemically modified derivatives. CDs complex the different compounds present in the culture medium which impair mycelial growth. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1558-1564, 2013 [ABSTRACT FROM AUTHOR]

Complex interactions between mycorrhizal helper bacteria (MHBs) and mycorrhizal fungi have rarely been studied in the context of drought. Separately, both MHB inoculation and moderate drought stress have previously shown to enhance desert truffle mycorrhization in Helianthemum almeriense plants, but the combined effect of both of them has not been evaluated yet. The goal of this study is to determine whether mycorrhization between Helianthemum almeriense and the desert truffle Terfezia claveryi can be triggered by applying Pseudomonas mandelii #29 under drought stress and whether this could improve plant water-relations. To investigate this, we evaluated the effect of the combination of MHB inoculation with two different water regimes (well-watered and water-deficit) over the mycorrhizal development, root hydraulic properties, gene expression of AQPs and plant hormones. The results showed that presence of P. mandelii under drought stress caused a synergistic increase of fungal colonization and a higher nutrient uptake. Although drought stress decreased root hydraulic conductivity (Lp r) regardless of whether plants were MHB-inoculated or not, this decrease was buffered in MHB-inoculated plants, concomintantly with regulation of plant hormones, such as abscisic acid, and aquaporin gene expression. Our results indicate that drought-mediated tripartite interactions (P. mandelii #29 x T. claveryi x H. almeriense) are beneficial for the plant to cope with water stress. • P. mandelii #29 is a MHB that increases the mycorrhizal colonization within the host roots especially under drought stress. • This higher mycorrrhizal colonization due to MHB is translated into higher water root hydraulic conductivity (Lp r). • This higher Lp r is associated with a modification of root hormone content and with the regulation of plant aquaporins. • The results indicate that drought-mediated tripartite interactions are beneficial for the plant to cope with water stress. [ABSTRACT FROM AUTHOR]