INVESTIGADORES
RUIZ Oscar Adolfo
artículos
Título:
Comparative symbiotic performance of native rhizobia of the Flooding Pampa and strains currently used for inoculating Lotus tenuis in this region
Autor/es:
SANNAZZARO A. I.; BERGOTTINI, V.M; PAZ R.C.; CASTAGNO, L N.; MENÉNDEZ A. B.; RUIZ O.A.; PIECKENSTAIN F.L.; ESTRELLA M.J.
Revista:
ANTON LEEUW INT. J. G.
Editorial:
SPRINGER
Referencias:
Año: 2011 vol. 99 p. 371 - 379
ISSN:
0003-6072
Resumen:
The Flooding Pampa (FP) is the most important area for cattle breeding in Argentina. In this region, persistence and yield of forage legumes such as red and white clover (Trifolium pratensis and T. repens) and lucerne (Medicago sativa) are strongly limited by soil salinity and alkalinity, which affect around 30% of the total area. Instead, naturalized narrow-leaf birdsfoot trefoil Lotus tenuis is the main forage legume in this region. As a legume, L. tenuis establishes a symbiotic relationship with soil rhizobia that convert atmospheric nitrogen into other forms that can be assimilated by the plant. Rhizobial strains currently used for inoculating L. tenuis in the FP are either 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 work 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. Non-redundant strains were identified by BOX-PCR fingerprinting among a collection of L. tenuis rhizobia native from saline-alkaline soils. A high genetic diversity was found, and 22 non-redundant strains were selected for infectivity tests. Some strains were highly infective and, under non-stressing conditions, their symbiotic performance exceeded that of strains currently used for field inoculation of L. tenuis. Moreover, the symbiotic performance of the native strain ML103 was considerably high under salt stress, a condition that strongly decreased the performance of strains currently used as inoculants. Free-living salt tolerance was not related to the type of soil from which bacteria were isolated. Thus, evaluating the symbiotic performance of rhizobia under salt stress, rather than their salt tolerance in the free-living state, seems a good criterion to select strains for inoculating L. tenuis in saline soils. Analysis of 16S rRNA RFLPs revealed that native strains are related to different rhizobial genera. On the contrary, the so far unclassified rhizobia currently used for field inoculation of L. tenuis only grouped with reference strains of 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.