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Promoting the forage Lotus tenuis is an appealing alternative to meet the needs for cattle production in the Flooding Pampa region, Argentina. This agricultural practice requires herbicides application to remove plant species competing with L. tenuis . The use of chemical compounds, in addition to the removal of native vegetation, eventually may change the diversity of other ecosystem components such as bacterial communities. The objectives of this work were to examine the effect of L. tenuis promotion on the bacterial community composition and on specific water-related soil variables, and to detect specific bacterial taxa responding to the L. tenuis promotion. In order to achieve these objectives, here we studied three different rangeland sites of the Flooding Pampa region. At each site, two paddocks were compared, one managed to promote the forage legume L. tenuis , and the other lacking of management history and hence, covered by natural grasses. To asses bacterial diversity we used 454-FLX pyrosequencing technology of the V4 region of the 16S rRNA gene, on genomic DNA extracted from soil samples. We obtained 135.918 sequences, representing 3187 Operational Taxonomic Units (OTUs) distributed in 12 phyla and 45 classes. Overall, the main identified components of the bacterial community at the Phylum level were Acidobacteria, followed by Verrucomicrobia, Planctomycetes and Chloroflexi. Our results suggest that 5-6 years of land use with L. tenuis promotion does not affect the microbial community structure in this ecosystem. NMDS ordination in two dimensions based on Bray–Curtis distances and PERMANOVA test did not show differences in bacterial community composition between paddocks promoted or not with L. tenuis, although differences among sites were detected. In parallel, Pearson’s correlation analysis suggested that L. tenuis promotion would indirectly affect members of classes Acidobacteria and Anaerolineae, through altering water-related soil properties. [ABSTRACT FROM AUTHOR]

Soil alkalinity is one of the most serious agricultural problems limiting crop yields. The legume Lotus tenuis is an important forage acknowledged by its ability to naturally grow in alkaline soils. To gain insight into the molecular responses that are activated by alkalinity in L. tenuis plants, subtractive cDNA libraries were generated from leaves and roots of these plants. Total RNAs of non-stressed plants (pH 5.8; E.C. 1.2), and plants stressed by the addition of 10 mM of NaHCO3 (pH 9.0; E.C. 1.9), were used as source of the driver and the tester samples, respectively. RNA samples were collected after 14 and 28 days of treatment. A total of 158 unigenes from leaves and 92 unigenes from roots were obtained and classified into 11 functional categories. Unigenes from these categories (4 for leaves and 8 for roots), that were related with nutrient metabolism and oxidative stress relief were selected, and their differential expression analyzed by qRT-PCR. These genes were found to be differentially expressed in a time dependent manner in L. tenuis during the alkaline stress application. Data generated from this study will contribute to the understanding of the general molecular mechanisms associated to plant tolerance under long-term alkaline stress in plants. [ABSTRACT FROM AUTHOR]

Abstract: The accumulation of putrescine (Put) and increased arginine decarboxylase (ADC, EC 4.1.1.19) activity levels in response to osmotic stress has been reported; however, the biological meaning of this increase remains unclear. To obtain new insights into these questions, we studied the drought response of a transgenic Lotus tenuis line that expresses the oat ADC gene, which is driven by the stress-inducible pRD29A promoter. This line contains high levels of Put with no changes in spermidine and spermine contents, even under water deficits. Our results indicate that the biochemical and morphological responses to dehydration correlate with the Put level and provide evidence that Put controls the ABA content in response to drought by modulating ABA biosynthesis at the transcriptional level. [Copyright &y& Elsevier]

Highlights: [•] Lotus seedlings are highly tolerant to water stress from deficit to waterlogging. [•] Lotus seedlings tolerate salinity and regulate Na+ concentration in tissue. [•] Lotus establishes early associations with AM fungi and Rhizobium. [•] Lotus seedlings acquire early imprints to respond better to future stress episodes. [Copyright &y& Elsevier]

Abstract: Lotus tenuis Wald et Kit and Lotus corniculatus L. are conspicuous elements of the agricultural landscape for cattle production. In South America, commercial L. tenuis stocks usually present contaminations with L. corniculatus, what brings about an important economical injure to the forage producers. A way to reduce or avoid loses is to assess the purity degree of L. tenuis seed lots before seeding. Methods so far described for the diagnosis of Lotus species when flowers are not available are lengthy, time consuming, need the implementation of sophisticated laboratories and are relatively expensive. It has been shown that Lotus species accumulate variable proanthocyanidins amounts, which can be easily visualized by a simple and rapid staining method. In this work, we demonstrate that the leaf PA content is a specific trait of L. tenuis and L. corniculatus and hence, it allows the unambiguous differentiation between both species, even at an early phenological stage. [Copyright &y& Elsevier]