Defining the wheat microbiome: towards microbiome-facilitated crop production

Wheat is one of the world’s most important crops, but its production relies heavily on agrochemical inputs which are notoriously harmful to the environment. It is well known that a multitude of microbes interact with eukaryotic organisms, including plants, and the sum of microbes and their functions associated with a given host is termed the microbiome. Plant-microbe interactions can be beneficial, neutral or harmful to the host plant. Over the last decade, with the development of next generation DNA sequencing technology, our understanding of the plant microbiome structure has dramatically increased. Considering that defining the wheat microbiome is key to leverage crop production in a sustainable way, here we describe how different factors drive microbiome assembly in wheat, including crop management, edaphic-environmental conditions and host selection. In addition, we highlight the benefits to take a multidisciplinary approach to define and explore the wheat core microbiome to generate solutions based on microbial (synthetic) communities or single inoculants. Advances in plant microbiome research will facilitate the development of microbial strategies to guarantee a sustainable intensification of crop production

Phosphorus efficiency for symbiotic N2 fixation of common bean <em>(Phaseolus vulgaris</em>) is affected by the form of phosphorus application in hydroaeroponic culture

International audiencePhosphorus uptake and utilisation by common beans (Phaseolus vulgaris) is essential for proper growth, and ensuring high yield and improved quality of the crop. To study the effects of the phosphorus application forms on the phosphorus use efficiency (PUE), for symbiotic nitrogen fixation (SNF), six common bean recombinant inbred lines (RIL) from the cross of BAT477 × DOR364 were inoculated by Rhizobium tropici CIAT 899, and submitted to five organic and inorganic treatments of P in hydroaeroponic culture in glasshouse in the south of France. The results showed significant differences in shoot and nodule biomass among inorganic and organic P sources with all RILs studied. In particular a significant increase was observed in shoot P content with bochevo and apatite compared to phytate and glycero P whereas RILs 83, 75 and 147 registered as a higher P uptake. A greater PUE was observed for RILs 34, 75 and 115 than other RILs with organic P especially under 75P (deficient P). A significant release of H+ was observed with organic P supply whereas bochevo buffered the pH which was suitable for nodulation and plant growth. In conclusion, the organic P forms could contribute to P uptake by nodulated common bean. Whereas bochevo was the most efficient source of P because of its positive effect on pH in hydroaeroponic culture

Synergy of anaerobic digestion and pyrolysis processes for sustainable waste management: A critical review and future perspectives

International audienceThe worldwide growing population, challenged by an ever-increasing global demand for food production, is also concomitant with increased waste production, particularly organic wastes. During the last decades, several waste processing technologies have been developed such as anaerobic digestion and pyrolysis. Recently, there has been an increased interest in creating industrial synergies by combining technologies in order to increase the efficacy of the process and improve waste management in the circular economy. In this review, we report on the importance of coupling anaerobic digestion and pyrolysis while providing evidence on the synergistic effects that may occur within such a combined waste bi-functional process. Specific attention has been paid to multiple symbiosis features that exist when coupling both processes, mainly 1) maximizing energy recovery through pyrolysis of solid digestate or feeding of the aqueous bio-oil phase in anaerobic digestion, 2) biogas purification by biochar or activated biochar, and 3) improving anaerobic digestion process stability by biochar addition to the system. In addition, the effects of coupling anaerobic digestate with biochar on soil biochemical properties and crop production were also presented. Improving the dual symbiosis of coupling anaerobic digestion and pyrolysis is likely to be a sustainable based approach that holds promise for wiser and more eco-efficient processing of organic wastes for versatile applications

Growth, nutrients concentrations, and enzymes involved in plants nutrition of alfalfa populations under saline conditions

International audienceIn order to assess the effect of salinity constraint on some agro-physiological and biochemical traits in Medicago sativa L., four Alfalfa populations (Tafilalet 1, Tafilalet 2, Demnate and Tata), originated from mountains and oasis of Morocco, were tested. The plants were grown under greenhouse conditions in pots filled with sand and peat under three salt treatments (0, 100 and 200 mM NaCl). Thereafter, plants were harvested 45 days after salt treatment and some agro-physiological and biochemical parameters related to salt tolerance, such as plant biomass, water content, membrane permeability, nutrients contents, nitrate reductase and acid phosphatase activities, were measured. Results showed that increase in NaCl concentration gradually reduced plant biomass, which displayed significant differences among the tested populations. Thus, Tata population appeared to be the most tolerant population to salinity, Tafilalet 1 population was the least tolerant one, while Tafilalet 2 and Demnate displayed moderate salinity tolerance. Variations in plant growth were associated with changes in physiological and biochemical parameters. Indeed, salinity caused a decrease in relative water content, perturbation of membrane permeability, and nutrients concentrations. Results also showed that salinity inhibited nitrate reductase activity in leaves of all tested populations, but acid phosphatase activity was increased in both leaves and roots of stressed plants. Salt tolerance of alfalfa populations was associated with high inorganic ion accumulation and the maintenance of membrane integrity and an adequate level in terms of nitrate reductase and acid phosphatase activities

Determination and partial purification of phosphatases and phytases enzymes in rhizobia strains isolated from <em>Phaseolus vulgaris</em>

International audienceThe impact of phosphorus on plant growth and symbiotic N2 fixation in common bean (P. vulgaris) plants was investigated in previous work with the estimation of phosphatase and phytases activities in nodules. The interactions between common bean genotypes and rhizobia strains were studied under controlled conditions in hydroponic culture. Three strains were isolated from nodules of common bean plants collected from farmer’s fields in the Marrakech region. The fourth strain was Rhizobium tropici CIAT899 used as a reference. Bean plants inoculated with these local rhizobial strains showed higher nodulation and an increase in phytase and phosphatase activities in their nodules under phosphorus sub-deficiency especially for RhM11 strain. The studied bean-rhizobia symbioses differ in their adaptation to phosphorus sub-deficiency conditions. We have not distinguished if the enzyme activity derived from the plant cell fraction of nodules or from the rhizobia. The present work was established to determine if the rhizobia strains possess the ability to produce phosphatases and phytases. Four strains isolated from Marrakech region were studied (RhM11, RhM13 and RhM14) in comparison with Rhizobium tropici CIAT 899 used as reference strain. The phosphatase activity was established by the method of Asmar and Gissel-Nielsen (1997), whereas the phytase activity was determined according to the method of Araujo et al. 2008. The strains were able to produce acid phosphatases and phytases. Their ability to produce phosphatases was higher than production of phytases. The extracellular phosphatase activity is very low compared to that produced by intracellular phosphatase in all strains. The highest phosphatase activity was noted for RhM11 and CIAT 899 strains (5.40 nmol min-1 g-1 and 4.62 nmol min-1 g-1; respectively). It may be concluded that the studied rhizobia strains play an important role in P. vulgaris-rhizobia symbiosis under phosphorus subdeficiency conditions

Identification at the species and symbiovar levels of strains nodulating Phaseolus vulgaris in saline soils of the Marrakech region (Morocco) and analysis of the otsA gene putatively involved in osmotolerance

9 páginas, 5 figuras, 1 tabla. -- The definitive version is available at http://www.elsevier.com/wps/find/journaldescription.cws_home/701801/descriptionSalinity is an increasing problem in Africa affecting rhizobia-legume symbioses. In Morocco, Phaseolus vulgaris is cultivated in saline soils and its symbiosis with rhizobia depends on the presence of osmotolerant strains in these soils. In this study, 32 osmotolerant rhizobial strains nodulating P. vulgaris were identified at the species and symbiovar levels by analysing core and symbiotic genes, respectively. The most abundant strains were closely related to Rhizobium etli and R. phaseoli and belonged to symbiovar phaseoli. A second group of strains was identified as R. gallicum sv gallicum. The remaining strains, identified as R. tropici, belonged to the CIAT 899T nodC group, which has not yet been described as a symbiovar. In representative strains, the otsA gene involved in the accumulation of trehalose and putatively in osmotolerance was analysed. The results showed that the phylogeny of this gene was not completely congruent with those of other core genes, since the genus Ensifer was more closely related to some Rhizobium species than others. Although the role of the otsA gene in osmotolerance is not well established, it can be a useful protein-coding gene for phylogenetic studies in the genus Rhizobium, since the phylogenies of otsA and other core genes are coincident at the species level.This research was funded by the AECID Spanish-Moroccan projects n◦A/018163/08 and A/025374/09, as well as the IFS project F/2826-3F. MF was supported by an AECID fellowship from the Spanish Ministry of External Affairs and Cooperation (MAEC). MHRB was the recipient of a JAE-Doc researcher contract from CSIC.Peer reviewe