Comparative symbiotic performance of native rhizobia of the Flooding Pampa and strains currently used for inoculating Lotus tenuis in this region

Abstract

The Flooding Pampa (FP) is the most important area for cattle breeding in Argentina. In this region, persistence and yield of typical forage legumes are strongly limited by soil salinity and alkalinity, which affect around 30% of the total area. Instead, naturalized Lotus tenuis is the main forage legume in this region. Rhizobial strains currently used for inoculating L. tenuis in the FP are exotic or native from non-saline soils of this region, their taxonomic identity being unknown. Assuming that rhizobia native from the most restrictive environments are well adapted to adverse conditions, the use of such isolates could improve the productivity of L. tenuis in the FP. Hence, the goal of this study was to evaluate the symbiotic efficiency of selected L. tenuis rhizobia native from the FP, as compared with strains currently used for field inoculation of this legume. Under non-stressing conditions, the symbiotic performance of native strains of FP exceeded those ones currently used for L. tenuis. Moreover, the symbiotic performance of the native strain ML103 was considerably high under salt stress, compared with strains currently used as inoculants. Analysis of 16S rRNA gene sequencing revealed that unclassified rhizobia currently used for field inoculation of L. tenuis and native strains grouped with the genus Mesorhizobium. As a whole, results obtained demonstrate that soils of the FP are a source of efficient and diverse rhizobia that could be used as a sustainable agronomic tool to formulate inoculants that improve forage yield of L. tenuis in this region.

Phosphate-solubilization mechanism and in vitro plant growth promotion activity mediated by Pantoea eucalypti isolated from Lotus tenuis rhizosphere in the Salado River Basin (Argentina)

“…The pellet was resuspended in 0·1 ml of sterile MilliQ water and cells were lysed by boiling for 15 min and then centrifuged at 13 500 g for 5 min. Finally, the supernatant was transferred to a clean tube and used as DNA source (Sannazzaro et al. 2010).…”

The Rhizobia-Lotus Symbioses: Deeply Specific and Widely Diverse

“…Among 103 root nodule isolates from L. tenuis trap plants grown in soils of the Salado River Basin (Argentina), a majority were related to genus Mesorhizobium : only 2 isolates seemed closely related to M. loti NZP2213 T , and the rest were more related to M. amorphae, M. mediterraneum, M. tianshanense or to strain NZP2037 ( Estrella et al, 2009 ; see Figure 1A ). Some of those have been classified in the new species M. sanjuanii ( Sannazzaro et al, 2018 ). A large portion of the isolates were grouped within genus Rhizobium , close to typical common bean symbionts R. gallicum, R. etli , and R. tropici ( Figure 1B ).…”

LOTUS spp: BIOTECHNOLOGICAL STRATEGIES TO IMPROVE THE BIOECONOMY OF LOWLANDS IN THE SALADO RIVER BASIN (ARGENTINA)

“…In this sense, the use of inoculants based on efficient native strains could be an affordable and sustainable resource to improve the yield of L. tenuis in this region. As a consequence, we evaluatedinoculants isolated from soils of the region of Salado River Basin (Estrella et al 2009;Sannazzaro et al, 2011). Moreover, low P soils levels is also an important issue in the Salado River Basin, and symbiotic associations could diminished its detrimental effect.…”

“…We isolated and characterized phosphate-solubilizing strains from a constrained environment in the region improve the implantation and persistence of L. tenuis. The most efficient isolate was identified as Pantoea eucalypti(M91 strain), a novel species in terms of plant growth-promoting rhizobacteria (Castagno et al, 2011). Inoculation of L. japonicus with this strain, alters the root, resulting in a herringbone pattern of root branching.…”