UNRAVELING THE IDENTITY OF EFFICIENT RHIZOBIA ASSOCIATED TO Lotus tenuis IN ARGENTINA

TORRES TEJERIZO, G. A.; SANNAZZARO, A.; HANSEN, L.; ESTRELLA, M.J.; PISTORIO, M.

Pucón

Workshop; Tercer Taller Latinoamericano de Rizobacterias Promotoras del Crecimiento Vegetal (PGPR2016); 2016

Universidad de la Frontera

Lotus tenuis is a keystone legume in the Salado River Basin in Buenos Aires Province, the most important region devoted to beef and dairy cattle production in Argentina. We had previously obtained a rhizobial collection from the mentioned region, showing that the great majority of the isolates from L. tenuis nodules were related to the genus Mesorhizobium. Two strains from different soils (BD68 from lowlands and BSA136 from saline-alcaline lowlands), that were highly efficient in Nitrogen fixation, were chosen for further studies given their potential for the development of L. tenuis inoculants. To obtain the draft genomes of both strains, Illumina sequencing libraries were constructed and sequenced. The Illumina reads were assembled by the GS de novo Assembler software and the genomes were annotated applying the Prokka pipeline.A comparative analysis of the 16S rRNA sequences of representative rhizobia showed that BD68 clustered with the M. loti/M. erdamanii/M. huakuii group and BSA136 was closely related to M. metallidurans. However, when we analyzed the sequences of other housekeeping genes we found that both isolates clearly separated from the forementioned species. We also performed in silico analysis of the similarity to related strains that have been completely sequenced. The comparison between BD68, BSA136 and each of the strains from the corresponding cluster in the 16S rRNA tree showed that our isolates presented ANIm (average-nucletide-identity) values under the 95-96% proposed threshold for the definition of a new species. Particularly, the ANIm value between BD68 and M. loti R7A was 93% while M. metallidurans and BSA136 featured an ANIm of 92%. These results suggest that our isolates constitute two new species within the genus Mesorhizobium.