The nodD1 gene of Sinorhizobium fredii HH103 Restores Nodulation Capacity on Bean in a Rhizobium tropici CIAT 899 nodD1/nodD2 Mutant, but the Secondary Symbiotic Regulators nolR, nodD2 or syrM Prevent HH103 to Nodulate with This Legume

Rhizobial NodD proteins and appropriate flavonoids induce rhizobial nodulation gene expression. In this study, we show that the nodD1 gene of Sinorhizobium fredii HH103, but not the nodD2 gene, can restore the nodulation capacity of a double nodD1/nodD2 mutant of Rhizobium tropici CIAT 899 in bean plants (Phaseolus vulgaris). S. fredii HH103 only induces pseudonodules in beans. We have also studied whether the mutation of different symbiotic regulatory genes may affect the symbiotic interaction of HH103 with beans: ttsI (the positive regulator of the symbiotic type 3 protein secretion system), and nodD2, nolR and syrM (all of them controlling the level of Nod factor production). Inactivation of either nodD2, nolR or syrM, but not that of ttsI, affected positively the symbiotic behavior of HH103 with beans, leading to the formation of colonized nodules. Acetylene reduction assays showed certain levels of nitrogenase activity that were higher in the case of the nodD2 and nolR mutants. Similar results have been previously obtained by our group with the model legume Lotus japonicus. Hence, the results obtained in the present work confirm that repression of Nod factor production, provided by either NodD2, NolR or SyrM, prevents HH103 to effectively nodulate several putative host plants.

GENETIC PARAMETERS IN SEED CHARACTERS OF Ormosia discolor UNDER DIFFERENT AMBIENT CONDITIONS

Ormosia discolor Spruce ex Benth. is a native tree of the Amazon with has fast growth and nodulation capacity, whose seeds are used for craftwork. The objective of this study was to estimate genetic parameters in seed characters of O. discolor at different ambient temperatures and to indicate superior matrices to compose seed lots. Seeds of 20 progenies selected from a population in the state of Amazonas were collected. Three experiments were performed under different ambient temperatures at the Seed Center laboratory/UFAM. Experiment 1 was performed at constant temperature of 30 °C. In experiment 2, seeds were submitted to a temperature of 35 °C. In experiment 3, after five months of freezing, the seeds were submitted to a temperature of 30 °C. The experimental design was completely randomized, consisting of 20 progenies, four replicates, and 25 seeds per plot. The germination characters evaluated were germination rate, mean germination time, and synchronization and speed germination indexes. Genetic and phenotypic variances and correlations, broad-sense heritability, and genetic gain through direct selection were estimated. O.discolor progenies showed significant genetic variability for most of the characters evaluated. High heritability and accuracy values (> 90%) were found for germination rates at all ambient temperatures. Matrices 2, 7, and 16 were superior for germination characters at all temperatures tested, being indicated for seedling production. Eighteen O. discolor seeds are sufficient for biometric analysis with accuracy of 95% in genotype selection.

TECHNOLOGICAL PARAMETERS OF SEEDS APPLIED TO THE SELECTION OF SUPERIOR MOTHER TREES FROM Ormosia discolor SPRUCE EX BENTH

ABSTRACT The study on the native species of fast growth and nodulation capacity, Ormosia discolor, intends to conserve genetic resources and make available seed lots of high vigor for seed orchards. This work evaluates the physical and physiological characteristics of seeds from 20 O. discolor trees as a subsidy for selecting superior mother trees. Twenty matrices selected from a population in the state of Amazonas were inventoried. Physical tests were performed on the seeds collected, including water content, biometrics, the weight of one thousand seeds, and coat permeability test. For vigor estimates and classification regarding seed storage, the seeds were frozen for five months. The germination test was carried out at a constant temperature of 30 °C. It was used a completely randomized design consisting of 20 mother trees, 4 replicates, and 25 seeds per plot. The germination characteristics evaluated were germination percentage, speed index, mean germination time, and synchronization index. Cut seeds are more efficient for determining water content. All biometric variables are representative for the selection of vigorous lots, with emphasis on geometric diameter, surface area, and sphericity of seeds. Species seeds were classified as orthodox and as having physical dormancy. The protrusion of the primary root is the best morphological characteristic for evaluating germination in the laboratory. The mother trees 7, 16, and 10 showed superior characteristics for dendrometric and technological data, being indicated for marking, phenological monitoring, and planting.

Influence de la fertilisation sur la capacité de nodulation de deux espèces de legumineuses, Vigna radiata L.Wilczek et Vigna unguiculata L.Walp (Fabaceae)

La présente étude a été conduite afin d’accroitre la capacité de nodulation des légumineuses. Pour ce faire, un dispositif de 6 traitements avec 3 répétitions a été mis en place. Il s’agit des traitements T1: sans apport de fertilisants; T2: apport d’azote sous forme d’urée; T3: apport de phosphore sous forme de triple superphosphate; T4: apport d’un mélange azote-phosphate dans les mêmes proportions;T5 : apport d’engrais complexe NPK; T6 : sol amendé avec de l’engrais organique sous forme de compost. L’évaluation de la capacité de nodulation a été faite en considérant deux paramètres après la floraison. Il s’agit du nombre et du poids des nodules. Les résultats de l’analyse statistique ont montré que contrairement au type de fertilisant, l’espèce de légumineuse n’influence pas la nodulation. Ainsi, le nombre et le poids de nodule les plus élevés sont obtenus avec la fertilisation organique. En outre, cette présente étude pourrait être étendue sur d’autres légumineusesMots clés : fertilisant, compost, azote phosphore, bactéries rhizobiaEnglish Title: Influence of fertilization on the nodulation capacity of two legume species, Vigna radiata L.Wilczek and Vigna unguiculata L.Walp (Fabaceae)This study was conducted to increase the nodulation capacity of legumes. To do this, a device of 6 treatments with 3 repetitions has been set up. These are T1 treatments: without fertilizer; T2: nitrogen supply in the form of urea; T3: phosphorus supply as triple superphosphate; T4: supply of a nitrogen-phosphate mixture in the same proportions, T5: complex NPK fertilizer input; T6: Soil amended with organic fertilizer in the form of compost. The evaluation of the nodulation capacity was made by considering two parameters after flowering. This is the number and weight of the nodules. The results of the statistical analysis showed that unlike the type of fertilizer, the leguminous species does not influence nodulation. Thus, the highest number and weight of nodules are obtained with organic fertilization. In addition, this present study could be extended to other legumes.Keywords: Fertilizer, compost, phosphorus rhizobia, bacteria.

Recurrent mutualism breakdown events in a legume rhizobia metapopulation

Bacterial mutualists generate major fitness benefits for eukaryotes, reshaping the host phenotype and its interactions with the environment. Yet, microbial mutualist populations are predicted to generate mutants that defect from providing costly services to hosts while maintaining the capacity to exploit host resources. Here, we examined the mutualist service of symbiotic nitrogen fixation in a metapopulation of root-nodulating Bradyrhizobium spp . that associate with the native legume Acmispon strigosus . We quantified mutualism traits of 85 Bradyrhizobium isolates gathered from a 700 km transect in California spanning 10 sampled A. strigosus populations. We clonally inoculated each Bradyrhizobium isolate onto A. strigosus hosts and quantified nodulation capacity and net effects of infection, including host growth and isotopic nitrogen concentration. Six Bradyrhizobium isolates from five populations were categorized as ineffective because they formed nodules but did not enhance host growth via nitrogen fixation. Six additional isolates from three populations failed to form root nodules. Phylogenetic reconstruction inferred two types of mutualism breakdown, including three to four independent losses of effectiveness and five losses of nodulation capacity on A. strigosus . The evolutionary and genomic drivers of these mutualism breakdown events remain poorly understood.

ALotus japonicusE3 ligase interacts with the Nod factor receptor 5 and positively regulates nodulation

SUMMARYPost-translational modification of receptor proteins is involved in activation and de-activation of signaling systems in plants. Both ubiquitination and deubiquitination have been implicated in plant interactions with pathogens and symbionts. Here we presentLjPUB13, a PUB-ARMADILLO repeat E3 ligase that specifically ubiquitinates the kinase domain of the Nod Factor receptor NFR5 and has a direct role in nodule organogenesis events inLotus japonicus. Phenotypic analyses of three LORE1 retroelement insertion plant lines revealed thatpub13plants display delayed and reduced nodulation capacity and retarded growth.LjPUB13expression is spatially regulated during symbiosis withMesorhizobium loti, with increased levels in young developing nodules. Thus,LjPUB13 is an E3 ligase with a positive regulatory role during the initial stages of nodulation inL. japonicus.

CHARACTERISATION OF SOYBEAN RHIZOBIAL STRAINS FROM JAVA AND SUMATRA

To get insight in the structure of soybean rhizobial population native to Indonesian soils, a thorough survey of the occurrence of the soybean rhizobia were conducted in several locations in Java and Sumatra. A total of 51 different isolates of rhizobial strains were characterised phenotypically based on their symbiotic properties, and genetically using amplified ribosomal DNA restriction analysis (ARDRA). Based on their nodulation capacity on both soybean and the native legume mungbean, these rhizobial strains could be divided into a group of 16 strains specific for soybean only and another group of 35 promiscuous strains that nodulated both leguminous plants. Based on ARDRA of PCRamplified 16S rDNA and 16S-23S rDNA spacer fragments, the rhizobial strains isolated from Java differed with those from Sumatra. Six Java isolates and only one Sumatra isolate were classified as Bradyrhizobium japonicum and these similar to that of B. japonicum strain USDA 110. All these B. japonicum strains were highly specific for soybean. One isolate from Java showed a rather unique position. The remaining strains from Java (20), which were symbiotically promiscuous strains, were clustered in another group. This group and another group containing most Sumatra isolates were distinct from B. japonicum USDA 110 and therefore it is tempting to speculate that these represent indigenous soybean rhizobial bacteria. Application of agricultural practices, such as enhancement of rhizobial population, to increase soybean production is still essential and noteworthy in Sumatra.

CHARACTERISATION OF SOYBEAN RHIZOBIAL STRAINS FROM JAVA AND SUMATRA

To get insight in the structure of soybean rhizobial population native to Indonesian soils, a thorough survey of the occurrence of the soybean rhizobia were conducted in several locations in Java and Sumatra. A total of 51 different isolates of rhizobial strains were characterised phenotypically based on their symbiotic properties, and genetically using amplified ribosomal DNA restriction analysis (ARDRA). Based on their nodulation capacity on both soybean and the native legume mungbean, these rhizobial strains could be divided into a group of 16 strains specific for soybean only and another group of 35 promiscuous strains that nodulated both leguminous plants. Based on ARDRA of PCRamplified 16S rDNA and 16S-23S rDNA spacer fragments, the rhizobial strains isolated from Java differed with those from Sumatra. Six Java isolates and only one Sumatra isolate were classified as Bradyrhizobium japonicum and these similar to that of B. japonicum strain USDA 110. All these B. japonicum strains were highly specific for soybean. One isolate from Java showed a rather unique position. The remaining strains from Java (20), which were symbiotically promiscuous strains, were clustered in another group. This group and another group containing most Sumatra isolates were distinct from B. japonicum USDA 110 and therefore it is tempting to speculate that these represent indigenous soybean rhizobial bacteria. Application of agricultural practices, such as enhancement of rhizobial population, to increase soybean production is still essential and noteworthy in Sumatra.

Relevance of Fucose-Rich Extracellular Polysaccharides Produced by Rhizobium sullae Strains Nodulating Hedysarum coronarium L. Legumes

ABSTRACTSpecific and complex interactions between soil bacteria, known as rhizobia, and their leguminous host plants result in the development of root nodules. This process implies a complex dialogue between the partners. Rhizobia synthesize different classes of polysaccharides: exopolysaccharides (EPS), Kdo-rich capsular polysaccharides, lipopolysaccharides, and cyclic β-(1,2)-glucans. These polymers are actors of a successful symbiosis with legumes. We focus here on studying the EPS produced byRhizobium sullaebacteria that nodulateHedysarum coronariumL., largely distributed in Algeria. We describe the influence of the carbon source on the production and on the composition of EPS produced byR. sullaeA6 and RHF strains. High-molecular-weight EPS preserve the bacteria from desiccation. The structural characterization of the EPS produced byR. sullaestrains has been performed through sugar analysis by gas chromatography-mass spectrometry. The low-molecular-weight EPS of one strain (RHF) has been totally elucidated using nuclear magnetic resonance and quantitative time-of-flight tandem mass spectrometry analyses. An unusual fucose-rich EPS has been characterized. The presence of this deoxy sugar seems to be related to nodulation capacity.