Effect of soil salinity on the root nodule microbiome of Lotus tenuis in the Flooding Pampa, Argentina

FIGUEROA-GALOIS IP; ESTRELLA MJ; PIECKENSTAIN FL; STALDER MS; RAMOS-DUARTE VA; SANNAZZARO AI

Quilmes

Congreso; 3er Congreso Latinoamericano de Ecología Microbiana; 2023

International Society of Microbial Ecology

Legumes can improve soil nutritional status by the nitrogen incorporation through the biological fixation process. This process occurs in root nodules in a highly specific association with some soil bacteria called rhizobia. In addition to rhizobia, endophytes non-rhizobia (ENR) have been found inside nodules by culture-independent methods such amplicon sequencing. Therefore, recent studies are focused on the role of ENR in the legume-rhizobia symbiosis. Lotus tenuis is a temperate perennial pasture which tolerates salinity and waterlogging conditions. Thus, L. tenuis is considered of high value to livestock production in Argentina. This research describes the microbiota inside root nodules of L. tenuis in two soils with contrasting salinity in the Flooding Pampa, Argentina: midland and saline lowland soils.We assessed the structure of the root nodule bacterial community of Lotus tenuis by 16S rRNA gene sequencing on the DNBSEQ platform. Raw sequences were filtered and annotated using Mothur software v.1.31.2. Alpha and beta diversities were calculated to identify diversity within and between samples respectively. Soil samples were also subjected to physicochemical analyses.1,388 OTUs with a similarity of 97% were identified. Alpha-diversity (Shannon index) was significantly lower (P = 0.001) in the saline lowland compared to the midland. 2 phyla, 3 classes, 5 orders, 8 families and 24 genera were significantly differentially abundant (P < 0.05) in some of the two soil conditions according to Wilcoxon rank-sum test. The genera Mesorhizobium, Ramlibacter and Amycolatopsis were identified as biomarkers in the midland by LEfSe (Linear discriminant analysis Effect Size) software analysis; on the other hand, Aminobacter, Adhaeribacter, Rhodococcus and Gemmobacter were biomarkers in the saline lowland. Electrical conductivity and ion contents (viz., Ca and Mg) were significantly different between the two soil conditions.Our results clearly show changes in the structure and proportion of bacterial communities between midland and saline lowland. Furthermore, some bacterial taxa were identified as biomarkers in some of the two soils. This study is a first approach to the understanding of the role of ENR in the legume-rhizobia symbiosis in soils with contrasting salinity.