Mario Honrubia

Antioxidant Activity of Edible Fungi (Truffles and Mushrooms): Losses during Industrial Processing

The antioxidant properties of two raw truffles (Terfezia claveryi Chatin and Picoa juniperi Vittadini) and five raw mushrooms (Lepista nuda, Lentinus edodes, Agrocybe cylindracea, Cantharellus lutescens, and Hydnum repandum) were tested by subjecting these truffles and mushrooms to different industrial processes (freezing and canning) and comparing them with common food antioxidants (alpha-tocopherol [E-307], BHA [E-320], BHT [E-321], and propyl gallate [E-310]) with regard to their ability to inhibit lipid oxidation. All of the truffles and mushrooms analyzed exhibited higher percentages of oxidation inhibition than did the food antioxidants according to assays based on lipid peroxidation (LOO*), deoxyribose (OH*), and peroxidase (H2O2). Frozen samples exhibited a small reduction in free radical scavenger activity, but the results did not show a significant difference (P < 0.05) with respect to the raw samples, while canned truffles and mushrooms lost some antioxidant activity as a consequence of industrial processing. All of the raw and frozen truffles and mushrooms except frozen Cantharellus improved the stability of oil against oxidation (100 degrees C Rancimat), while canned samples accelerated oil degradation. Antioxidant activity during 30 days of storage was measured by the linoleic acid assay, and all of the samples except canned Terfezia, Picoa, and Hydnum showed high or medium antioxidant activity. The Trolox equivalent antioxidant capacity assay was used to provide a ranking order of antioxidant activity as measured against that of Trolox (a standard solution used to evaluate equivalent antioxidant capacity). The order of raw samples with regard to antioxidant capacity was as follows (in decreasing order): Cantharellus, Agrocybe, Lentinus, Terfezia, Picoa, Lepista, and Hydnum. Losses of antioxidant activity were detected in the processed samples of these truffles and mushrooms.

Changes and effects of a natural fire on ectomycorrhizal inoculum potential of soil in a Pinus halepensis forest

Abstract A typically mediterranean forest of Pinus halepensis wass tudied. During two years following fruiting fungal species, the number of sclerotia in soil, and the percentages and types of mycorrhizas present were determined. In burned stands ascomycetes were typical carbonicolous while basidiomycetes were strongly reduced. The sclerotia extracted from soils were mainly Cenococcum . The number of sclerotia in burned stands was greater than in unburned stands. Seven types of mycorrhizas were recognized in Pinus halepensis root systems from bioassays: Cenococcum , E-strain, Rhizopogon, Suillus, Tuber, Xerocomus , and one non-identified. Nearly 100% of the roots were colonized by mycorrhizal fungi. Ectendomycorrhizas represented 50–90% of the total number. The predominant type is ectendomycorrhizas formed by ascomycetes included in the E-strain group.

Morphological characterization of the mycorrhiza formed by Helianthemum almeriense Pau with Terfezia claveryi Chatin and Picoa lefebvrei (Pat.) Maire

This work presents the first anatomical description of the mycorrhizal systems of Helianthemum almeriense, and of the structure and ultrastructure of the mycorrhizae formed by this plant species with the ascomycetes Terfezia claveryi and Picoa lefebvrei. Four different mycorrhizal systems are described, the club-shaped mycorrhiza being the most abundant. The type of mycorrhiza formed depended on the mycorrhiza culture conditions, but not on the fungal species. For both fungal species, H. almeriense formed an endomycorrhiza in natural field conditions, an ecto- and ectendomycorrhiza without a sheath in pot cultures, and an ectomycorrhiza with a characteristic sheath and Hartig net in in vitro cultures. This is the first report of a typical sheath in Helianthemum-desert truffle mycorrhizal associations. The results support the idea that culture conditions can induce changes in mycorrhiza morphology and that there is no clear barrier between the two main types of mycorrhiza organization in Helianthemum species. The ultrastructural study confirmed the regular presence of T. claveryi intracellular hyphae in direct contact with the host wall, a localization which seems to be a characteristic of the T. claveryi mycorrhiza organization. The P. lefebvrei mycorrhiza organization was characterized by intracellular hyphae with large amounts of electron-dense globules, probably with a lipidic content, and a warty ornamentation on the wall of the root external hyphae.

Microsite and mycorrhizal inoculum effects on the establishment of Quercus coccifera in a semi-arid degraded steppe

Abstract Alpha grass (Stipa tenacissima) steppes are widely distributed within the semi-arid areas of the Mediterranean Basin, and represent a degraded stage of vegetation. We evaluated the effect of S. tenacissima tussocks and nursery inoculation with mycorrhizae on the survival of the native shrub Quercus coccifera. Experiments were carried out in three steppes located in semi-arid southeastern Spain. Survival during the first months after plantation was significantly higher in the surroundings of S. tenacissima tussocks than in open areas between the tussocks. We did not find any effect of nursery inoculation on seedling survival. This effect may be related to the fact that the used fungal strain did not survive the drought summer conditions in the study area. Our results support the idea of a facilitative effect of S. tenacissima on introduced shrubs, which may be related to improved environmental conditions in tussock microsites. However, this effect may not be enough for the establishment of seedlings in years with below-average rainfall and a strong summer drought.

Biotechnology and Cultivation of Desert Truffles

Among the ascomyces truffles, there are several genera with an excellent record as edible fungi, and two of these are of considerable economic importance: Terfezia and Tuber. Of these two genera, only Tuber had been cultivated commercially (for decades), until now. More recently, biotechnological methods on fungal inoculum and mycorrhizal plant production, as well as plantation management, have been developed to cultivate, for the first time, some species of the Terfezia genus (Honrubia et al. 2001, 2005; Morte et al. 2004, 2006). These procedures are presented in this chapter. Here, we attempt to evaluate conclusions on the basis of recent truffle production data from the first field plantations. The genus Terfezia belongs to the so-called “desert truffles” which are a complex family of mycorrhizal hypogeous fungi, mainly containing species of the genera Terfezia, Picoa, Tirmania and Tuber. Their geographical distribution is limited to arid and semiarid lands, mostly in countries around the Mediterranean basin, such as: southern Spain, Portugal, Italy, France, Hungary, Turkey, from Morocco to Egypt, Israel, the Arabian Peninsula, Iran, Iraq, Libya, Syria, and Kuwait. In addition, some desert truffle species have been found in South Africa (Botswana) (Marasas and Trappe 1973), in North America and Japan (Trappe and Sundberg 1977), and China (Wang, unpublished data). Generally, the regions where desert truffles grow have an annual rainfall which ranges from 50 to 380 mm. The truffle season produces good yields if the rainfall ranges from 70 to 120 mm in North African countries and from 100 to 350 mm in countries of southern Europe. The rainfall distribution is very important as far as both quantity and the time of the rainfall are concerned; that is, no later than the beginning of December in North African and Middle Eastern countries and no later than the beginning of October in countries of southern Europe.

Desert Truffle Cultivation in Semiarid Mediterranean Areas

This chapter focusses on showing some taxonomic and ecological characters of the main desert truffle species in Spain as well as the main biotechnological procedures followed to produce mycorrhizal plants with some of these fungal species. The full micropropagation protocol of the host plant Helianthemum violaceum is described for the first time. Five different ways of producing mycorrhizal synthesis between desert truffles and the Helianthemum species are reported, according to the type of fungal inoculum, plant source and culture conditions used. Finally, a management protocol for the established desert truffle plantations is discussed. Irrigation, one of the most important factors considered for successful cultivation, should be applied at the end of the summer during dry years when rainfall is less than 150 mm and for a second time at the beginning of the fruiting season in very dry years.

Seasonal variation of vesicular-arbuscular mycorrhizae in eroded soils from southern Spain

A survey was carried out of the seasonal variations in the number of spores in the soil and of the percentage of root infection. The stage of development of the host plants, environmental variations and physicochemical characteristics of the soil were taken into account. Fifteen plants valid as forage and adaptable to semi-arid conditions and poor soils were selected. In general, the maximum spore density was reached in the fruit-bearing period of the plants. It remained high during autumn, fell to a minimum in winter and tended to increase in spring. Root infection was at a maximum when the plants flowered, after which it decreased to a minimum in summer.

Basidiospore viability in stored slurries

The viability and activity of basidiospores corresponding to 14 species of ectomycorrhizal fungi stored in slurries was studied. The methods used were the aceto-iron-haematoxylin nuclear stain to determine basidiospore viability and the FDA stain to determine basidiospore activity and dormancy. The basidiospores of Cortinarius sp., Hebeloma sp., Inocybe sp., Laccaria bicolor, Laccaria laccata, Lactarius deliciosus, Lactarius sanguifluus, Rhizopogon roseolus, Russula delica, Russula sanguinea, Suillus collinitus, Suillus granulatus, Suillus variegatus and Tricholoma terreum were suspended in slurries in duplicate experiments and half were stored at 3–4 °C and the other half at −15°. Spore viability and activity was tested after 180 days of storage. Loss of viability was least in species of Rhizopogon and Suillus , but data showed an almost total loss of viability in both refrigerated and frozen slurries of all fungi.

Influence of vesicular-arbuscular mycorrhizal infection and P addition on growth and P nutrition of Anthyllis cytisoides L. and Brachypodium retusum (Pers.) Beauv.

The effect of P applications and mycorrhizal inoculation on the growth and P nutrition of Anthyllis cytisoides L. (Fabaceae) and Brachypodium retusum (Pers.) Beauv. (Poaceae) was studied. Both plants are widely distributed and well adapted to semi-arid habitats in southern Spain. In all treatments, even with high P doses, mycorrhizal plants showed a higher concentration of phosphorus in their tissues than non-mycorrhizal plants. Mycorrhizal inoculation enhanced the growth of the plants when no P was applied. At high P addition, non-mycorrhizal plants showed higher growth than mycorrhizal plants. The response of each plant type to P application was somewhat different.

Pure culture studies on Tetracladium

Tetracladium marchalianum , type species of the genus, T. apiense, T. furcatum, T. setigerum, T. breve n. sp., T. palmatum n. sp. and T. maxilliforme have been studied in pure culture. T. marchalianum, T. maxilliforme and T. setigerum are neotypified. A key to species is provided.