Are Northwestern Patagonian “mallín” wetland meadows reservoirs of Ochetophila trinervis infective Frankia?

Abstract

Mallín" (plural mallines) is a particular kind of wetland occurring in Patagonian steppe and forests. In Northwest Patagonia, mallines are humid meadows with high net primary production. It was previously found that a mallín soil in the steppe devoid of actinorhizal plants had a higher Frankia nodulation capacity in Ochetophila trinervis (sin. Discaria trinervis) than other soils in the region. Under the hypothesis that mallín wetland meadows are reservoir of infective Frankia, we studied the Frankia nodulation capacity in O. trinervis of 12 mallín and their neighbouring steppe soils, by using plant bioassays. A qualitative plant bioassay showed that infective Frankia was present in most soils. The number of nodules per plant in seedlings inoculated with mallín soils was negatively correlated with soil water content while the opposite was true for plants inoculated with soils from neighbouring steppe. A quantitative bioassay was performed with eight representative soils, selected according to the number of nodules per plant produced in the qualitative assay and to the presence or not of different actinorhizal plants at the sites. Frankia nodulation units per cm 3 of soil (NU) in mallín soils were higher than those in steppe. Water and organic matter content of soils were correlated with the higher nodulation capacity of mallines, which may account for the saprotrophic growth of Frankia in soils. The symbiosis was effective in plants inoculated with all soil samples. These results suggest that Northwestern Patagonian mallín wetland meadows are reservoirs of infective and effective Frankia propagules in O. trinervis.

Alien vs. native plants in a Patagonian wetland: elemental ratios and ecosystem stoichiometric impacts

“…The roots were cleared in KOH 10% (w/v) acidified with HCl 5% (v/v) and stained with trypan blue (Brundrett et al 1994); they were then cut into 1-cm pieces. Typical structures of arbuscular mycorrhizal (AM) colonization (hyphae, arbuscules, vesicles, coils) and of dark septate fungi (DSF) (dark hyphae, microsclerotia, hyaline hyphae) were identified and quantified according to their presence-absence in the microscope field (Cardoso et al 2010) using a direct microscope Olympus BX50 at 4009.…”

Ochetophila-infective Frankia colonization patterns of volcanic ash in Patagonia

“…Survival is considered a critical ecological process which involves the interaction of organisms that form part of the biological legacies and the disturbance processes (Dale et al 2005). Soilborne Frankia from Patagonia can survive for very long periods in air-dried soils and in submerged soils with seasonal drought (Chaia et al 2007;Cardoso et al 2010). The precise mechanisms of the survival capacity of Frankia in Patagonian soils under harsh conditions are beyond the scope of this study, though they might be due to mechanisms of avoidance such as hyphal growth into deeper soil, or tolerance to desiccation (Burleigh and Dawson 1994b) and to other environmental stresses (such as changes in pH, salinity and temperature) explained by molecular and protein key determinants (Ghedira et al 2018;Diagne et al 2020).…”

“…The members of the genus Frankia belong to the phylum Actinobacteria that nodulate actinorhizal plants. Soilborne Frankia populations are common in northwest Patagonia and may associate with native Rhamnaceae plants (Chaia et al 2006;Cardoso et al 2010). This kind of symbiosis plays an important role in the region due to the amount of nitrogen fixed by the bacteria and supplied to the host plants (Chaia et al 2019).…”

Vertebrate faeces as sources of nodulating Frankia in Patagonia

“…The occurrence of strains infecting Ochetophila trinervis (sin. Discaria trinervis) in soils without actinorhizal plants may due to water transport because Frankia has been found in sediments of glacial lakes (Chaia et al 2005) and in wetland meadow soils in valley bottoms subjected to periodical flooding (Cardoso et al 2010). Ochetophila trinervis, is a plant that has potential in the reclamation of disturbed land in this part of Patagonia (Reyes et al 2011).…”