Soil Microfungi of Israeli Deserts: Adaptations to Environmental Stress

Abstract

This chapter presents the results of mycological studies conducted in the soils of Israeli deserts covering more than 60% of the country, with annual rainfall ranging from more than 300 mm in the northwest to about 25 mm in the extreme south. In spite of hostility, the desert soils maintained a comparatively rich culturable fungal diversity—more than 420 species. This diversity has displayed remarkable adaptive strategies to harsh desert stresses reflected in diverse phenotypic and biological traits: (a) melanin-containing fungi with large, thick-walled, and multicellular conidia dominated the majority of topsoil communities and lost their dominant position either to the species with picnidial fruit bodies in the less UV-radiated area located 190 m below sea level or to thermophilic Aspergillus fumigatus in the extremely hot localities; (b) melanized species with protective spore morphology prevailed also in the deep layers of bare playa profiles characterized by high salinity and strongly limited water infiltration; (c) mesic Penicillium spp. dominated in the middle depths of sandy and playa profiles due to the ability of their abundantly produced small spores to penetrate during water infiltration; (d) aspergilli (mainly A. fumigatus) and sexual ascomycetes with perithecial fruit bodies comprised a basic part of thermotolerant mycobiota; (e) in most hostile environments, the structure of microfungal communities was subjected to relatively small spatiotemporal variations, while the density of fungal isolates fluctuated drastically, with highly positive dependence on organic matter content; and (f) distinct genetic structure and mode of reproduction characterized the population of A. nidulans from southern Negev.