Abstract
Betula aetnensis is an endemic tree of high conservation value, which thrives on the nutrient-poor volcanic soils of Mount Etna. Since plant–microbe interactions could play a crucial role in plant growth, resource uptake, and resistance to abiotic stresses, we aimed to characterize the root and rhizosphere microbial communities. Individuals from natural habitat (NAT) and forest nursery (NURS) were surveyed through microscopy observations and molecular tools: bacterial and fungal automated ribosomal intergenic spacer analysis (ARISA), fungal denaturing gradient gel electrophoresis (DGGE). B. aetnensis was found to be simultaneously colonized by arbuscular (AM), ectomycorrhizal (ECM), ericoid (ERM) fungi, and dark septate endophytes (DSE). A high diversity of the bacterial community was observed whilst the root fungal assemblage of NAT plants was richer than that of NURS. Root and rhizosphere fungal communities from NAT plants were characterized by Illumina MiSeq sequencing. Most of the identified sequences were affiliated to Helotiales, Pezizales, and Malasseziales. Ascomycota and Basidiomycota dominated roots and rhizosphere but differed in community structure and composition. ECM in the roots mainly belonged to Tylospora and Leccinum, while Rhizopogon was abundant in the rhizosphere. The Helotiales, including ERM (mostly Oidiodendron) and DSE (mostly Phialocephala), appeared the dominant component of the fungal community. B. aetnensis harbors an extraordinarily wide array of root-associated soil microorganisms, which are likely to be involved in the adaptation and resistance mechanisms to the extreme environmental conditions in volcano Etna. We argue that nursery-produced seedlings could lack the necessary microbiota for growth and development in natural conditions.
Highlights
Betula aetnensis Raf. (Family Betulaceae) is a tree species endemic to Sicily, where it mostly thrives on the north-eastern slopes of volcano Etna, from 1400 to 2100 m a.s.l. [1,2].Betula aetnensis is thought to be originated from Betula pendula Roth., a European-wide distributed birch [3]
Soils from the natural habitat were not identical sampled in the same area and they were much poorer than soils from the forest nursery (NURS)
Such large differences are due to the fact that the soils for the forest nursery came from lava flows older than those in the natural habitat, and were more developed and fertile, as well as deeper
Summary
Betula aetnensis Raf. (Family Betulaceae) is a tree species endemic to Sicily, where it mostly thrives on the north-eastern slopes of volcano Etna, from 1400 to 2100 m a.s.l. [1,2].Betula aetnensis is thought to be originated from Betula pendula Roth., a European-wide distributed birch [3]. Despite its taxonomic rank is still under debate, B. aetnensis is considered a separated taxon in the Italian flora [4]. This species has an excellent ability to colonize volcanic substrates, where it plays a prominent role as a typical pioneer species at the beginning of the primary succession, showing high ecological importance. The adaptation to such harsh habitats by B. aetnensis reflects its
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