Phylogenomic Review of Root Nitrogen-Fixing Symbiont Population Nodulating Northwestern African Wild Legumes

The present review discusses the phylogenomic diversity of root nitrogen-fixing bacteria associated to wild legumes under North African soils. The genus Ensifer is a dominant rhizobium lineage nodulating the majority of the wild legumes, followed by the genus Rhizobium and Mesorhizobium. In addition, to the known rhizobial genera, two new Microvirga and Phyllobacterium genera were described as real nodulating and nitrogen-fixing microsymbiotes from Lupinus spp. The promising rhizobia related to nitrogen fixation efficiency in association with some legumes are shared. Phylogenetic studies are contributing greatly to our knowledge of relationships on both sides of the plant-bacteria nodulation symbiosis. Multiple origins of nodulation (perhaps even within the legume family) appear likely. However, all nodulating flowering plants are more closely related than previously suspected, suggesting that the predisposition to nodulate might have arisen only once. The origins of nodulation, and the extent to which developmental programs are conserved in nodules, remain unclear, but an improved understanding of the relationships between nodulin genes is providing some clues

Draft Genome Sequence of Phyllobacterium endophythicum mTS5, Isolated from Lupinus micranthus in Tunisia

We report here the draft genome sequence of Phyllobacterium endophyticum mTS5, isolated from a Lupinus micranthus root nodule. The genome consists of 5,454,168 bp, with a GC content of 57%, and contains 5,676 protein-coding sequences

Characterization of Rhizobial Bacteria Nodulating Astragalus corrugatus and Hippocrepis areolata in Tunisian Arid Soils

Fifty seven bacterial isolates from root nodules of two spontaneous legumes (Astragalus corrugatus and Hippocrepis areolata) growing in the arid areas of Tunisia were characterized by phenotypic features, 16S rDNA PCR-RFLP and 16S rRNA gene sequencing. Phenotypically, our results indicate that A. corrugatus and H. areolata isolates showed heterogenic responses to the different phenotypic features. All isolates were acid producers, fast growers and all of them used different compounds as sole carbon and nitrogen source. The majority of isolate grew at pHs between 6 and 9, at temperatures up to 40°C and tolerated 3% NaCl concentrations. Phylogenetically, the new isolates were affiliated to four genera Sinorhizobium, Rhizobium, Mesorhizobium and Agrobacterium. About 73% of the isolates were species within the genera Sinorhizobium and Rhizobium. The isolates which failed to nodulate their host plants of origin were associated to Agrobacterium genus (three isolates)

Detection of Bactrocera oleae (Diptera: Tephritidae) DNA in the gut of the soil species Pseudoophonus rufipes (Coleoptera: Carabidae)

Pest control service provided by natural enemies of Bactrocera oleae, the key pest of the olive tree, is nowadays recognized as fundamental. B. oleae has developed resistance to common insecticides, and negative effects both on consumers' health and non-target species arc the major drawbacks of conventional control strategics. Carabid beetles are potential B. oleae pupae predators, but their predation on field still need to be assessed. We tested adult Pseudoophonus rufipes, a species known to be active in olive orchard when pest pupae are abundant in the soil, in order to detect B. oleae pupae consumption at different post feeding times for both male and female carabids. An already existing protocol was used for detecting B. oleae mtDNA sequences of the cytochrome oxidase subunit I gene in carabids' gut, and its versatility improved. B. oleae mtDNA was detected up to 20 h after pupa ingestion with a high percentage of success, without significant differences between sexes and pair primers used. Prey DNA extraction was tested from both dissected and non-dissected carabids, obtaining comparable results. The trapping system used to collect carabids for molecular assays and the new elements introduced in the protocol represent cost-effective solutions that may be beneficial for future laboratory trials and, mostly, for the analysis of field-collected predators. Fostering the investigation of soil predators in olive orchard may increase the design of conservation control strategies against B. oleae.Scuola Superiore Sant’Anna, Pisa, Italy (PhD Programme in Agrobiodiversity)

Soil Properties shape species diversity and community composition of native arbuscular mycorrhizal fungi in Retama raetam roots growing on arid ecosystems of Tunisia

The aim of this study was to identify the major environmental factors affecting the Arbuscular Mycorrhizal Fungi (AMF) diversity and community composition in the roots of Retama raetam growing on arid ecosystems of Tunisia AM Fungi were assessed by cloning and sequencing of the AMF SSU rRNA gene and therefore checked against NCBI GenBank and MaarjAA4 database. Thirteen operational taxonomic units (OTUs) were identified in R. raetam roots and AMF community was dominated by Glomeraceae. Of the totality of OTUs, ten matched previously known virtual taxa (VTX) and 3 OTUs were treated as novel VT and grouped into 3 putative new AMF taxa (pNTX). Correlation analysis reported that high available phosphorus content and high electrical conductivity in the soil decrease AMF richness and diversity. Interestingly, Principal Component Analysis (PCA) and Monte Carlo permutation tests on Canonical Correspondence Analysis (CCA) indicated that soil physic-chemical properties such as soil total nitrogen (TN), soil-available P, EC, and soil texture affected the AMF community composition. No significant relation was found between AMF distribution and soil organic carbon (OC) and soil pH. Our findings provide insights into the nature of AMF communities colonizing R. raetam roots and help to link fungal distribution to specific soil properties, which could be exploited in the identification of a wider variety of fungal strains as potential inoculants for rehabilitation and restoration program