Abstract
Fungal endophytes have shown to affect plant growth and to confer stress tolerance to the host; however, effects of endophytes isolated from water plants have been poorly investigated. In this study, fungi isolated from stems (stem-E) and roots (root-E) of Mentha aquatica L. (water mint) were identified, and their morphogenetic properties analysed on in vitro cultured Arabidopsis (L.) Heynh., 14 and 21 days after inoculation (DAI). Nineteen fungi were analysed and, based on ITS analysis, 17 isolates showed to be genetically distinct. The overall effect of water mint endophytes on Arabidopsis fresh (FW) and dry weight (DW) was neutral and positive, respectively, and the increased DW, mainly occurring 14 DAI, was possibly related to plant defence mechanism. Only three fungi increased both FW and DW of Arabidopsis at 14 and 21 DAI, thus behaving as plant growth promoting (PGP) fungi. E-treatment caused a reduction of root depth and primary root length in most cases and inhibition-to-promotion of root area and lateral root length, from 14 DAI. Only Phoma macrostoma, among the water mint PGP fungi, increased both root area and depth, 21 DAI. Root depth and area 14 DAI were shown to influence DWs, indicating that the extension of the root system, and thus nutrient uptake, was an important determinant of plant dry biomass. Reduction of Arabidopsis root depth occurred to a great extent when plants where treated with stem-E while root area decreased or increased under the effects of stem-E and root-E, respectively, pointing to an influence of the endophyte origin on root extension. M. aquatica and many other perennial hydrophytes have growing worldwide application in water pollution remediation. The present study provided a model for directed screening of endophytes able to modulate plant growth in the perspective of future field applications of these fungi.
Highlights
Plants are sessile organisms characterized by developmental plasticity, which allows them to adapt to environmental conditions
Fungal endophytes were isolated from stems and roots of 20 individuals of M. aquatica growing in a water stream siding Demonte river, in the Valle Stura di Demonte, Cuneo, Italy (44°18.3500N, 7°22.2960E; 680 m a.s.l.)
ITS sequence data analysis led to the genetic differentiation of 17 isolates, among these, nine fungi showed a 100% identity with sequences deposited in GenBank (Table 1) and corresponded to the following species: Aureobasidium pullulans G
Summary
Plants are sessile organisms characterized by developmental plasticity, which allows them to adapt to environmental conditions. Endophytic Fungi Modulating Plant Growth alone, but are a component of the “holobiont”, “the host organism and all its symbiotic microbiota” [1] with associated microorganisms having a remarkable role in plant adaptation and survival [1]. A large group of plant-associated microorganisms is represented by endophytic fungi According to Brundrett [3], mycorrhizal associations differ from the non-mycorrhizal ones because of the construction of a specialized interface to transfer nutrients between hosts. Whilst the development of mycorrhizal fungi is restricted to roots, non-mycorrhizal endophytes may grow into the roots (e.g. the dark septate endophytes (DSE) [4]) or the stem-leaf system, or both [2]
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