IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

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17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Session Details: Wednesday 30 November 2011 Plenary Session 5 0900 - 1030 Authors: Doreen Fischer 1 , Barbara Pfitzner 1 , Veronica M. Reis 2 , Jean L. Simoes-Araújo 2 , Michael Schmid 1 , Esperanza Martinez-Romero 3 , Jose I. Baldani 2 , Anton Hartmann 1 1 Helmholtz Zentrum Munich, German Research Center for Environmental Health, Research Unit Microbe-Plant Interactions, Neuherberg, Germany 2 EMBRAPA-CNPAB Seropedica, Seropédica, RJ, Brazil 3 Centro de Ciencias Genomicas, Universidad Nacional Autonoma de Mexico, UNAM, Cuernavaca, Morelos, Mexico Presentation Title: Molecular characterization of the active diazotrophic community in uninoculated and inoculated field-grown sugarcane (Saccharum sp.) Presentation Time: 1000 – 1030 Certain cultivars of sugar cane are known for their high potential of supporting biological nitrogen fixation. Although many different diazotrophic bacteria have been isolated from sugar cane and demonstrated to colonize roots, stems and leaves of these plants in considerable number, no clear evidence exists about the type of diazotrophic bacteria which fixes nitrogen in planta and about the locations of nitrogen fixation activity. To identify active diazotrophs in field grown sugarcane, 16S rRNA and nifH transcript analyses were applied. This should help to better understand the basis of the biological nitrogen fixation (BNF) activity in a high nitrogen fixing sugarcane variety. A field experiment using the sugarcane variety RB 867515 was conducted in Seropédica, RJ, Brazil, receiving the following treatments: unfertilised and fertilised controls without inoculation, unfertilised with inoculation. The five-strain mixture of diazotrophic bacteria containing Gluconacetobacter diazotrophicus, Burkholderia tropica, Herbaspirillum seropedicae, Herbaspirillum rubrisubalbicans and Azospirillum amazonense, developed by EMBRAPA-CNPAB, was used as inoculum. Root and leaf sheath samples were harvested in the third year of cultivation (after receiving an inoculum at the beginning of the season) to analyse the 16S rRNA and nifH transcript diversity. In addition to nifH expression from Gluconacetobacter spp. and Burkholderia spp., a wide diversity of nifH transcripts from previously uncharacterised Ideonella / Herbaspirillum related phylotypes in sugarcane shoots as well as Bradyrhizobium sp. and Rhizobium sp. in roots were found. These results were confirmed using 16S cDNA analysis. From the inoculated bacteria, only nifH transcripts from G. diazotrophicus and B. tropica were detected in leaf sheaths and roots at the time of harvest in late summer, respectively. Thus, well known as well as yet uncultivated diazotrophs were found active in sugarcane roots and stems using molecular analyses. Two strains of the inoculum mix were found active at the late summer harvest. 66 2011
17 th International Congress on Nitrogen Fixation Fremantle, Western Australia 27 November – 1 December 2011 Session Details: Wednesday 30 November 2011 The Cape Floristic Region (CFR) has a mosaic of soil types derived from parent materials including sandstone, granite, limestone and shale. It has high species diversity, varying among soil types and environmental gradients. Among legumes, particular lineages appear to be restricted to one or few substrates, raising questions on whether their species distribution is predetermined by symbiotic bacteria. We hypothesized that rhizobial isolates from indigenous legumes would cluster phylogenetically according to soil types and/or host legume. Rhizobia were isolated from nodules collected from 87 species in over 12 genera belonging to tribes Crotalarieae, Indigofereae, Phaseoleae, Podalyrieae and Psoraleae. Sequenced data using the 16S rRNA gene revealed the presence of both α- (Bradyrhizobium, Mesorhizobium, Rhizobium, Synorhizobium) and β-rhizobia (Burkholderia), the latter nearly exclusive to the tribe Podalyrieae. Mesorhizobium was isolated from Aspalathus, Otholobium, Psoralea, Indigofera and Argyrolobium species collected from all substrates, while Bradyrhizobium species were isolated from Indigofera and Tephrosia species collected from granite and sandstone-derived soils. Burkholderia species were isolated from Podalyria, Amphithalia and Rafnia species collected from granite, coastal sand and limestone derived soils. These data were confirmed by immunogold labeling of the bacteria in nodule sections with an antibody specific to Burkholderia (Elliott et al. 2007a). Furthermore, a GFP-tagged strain of B. tuberum STM678, which has previously been shown to nodulate species of Cyclopia (tribe Podalyrieae native to the CFR; Elliott et al. 2007b), could effectively nodulate species of Podalyria and Virgilia. The phylogenies of the rhizobia isolates from the 16S rRNA gene sequence and of the host legumes from literature are discussed in relation to the evolutionary relationships of the symbiotic partners. The available data suggest that the soil types do not influence the distribution of rhizobia in the CFR. Elliott, G. N. et al. 2007a. New Phytol. 173:168-180. Elliott, G. N. et al. 2007b Ann. Bot. 100:1403-1411. Concurrent Session 10 – Ecology of RNB 1100 – 1230 Authors: Oscar Dlodlo 1 , A. Muthama Muasya 1 , Janet I. Sprent 2 , Euan K. James 3 , Wen-Ming Chen 4 , Samson B.M. Chimphango 1 1 University of Cape Town, Botany Department, Private Bag X3 Rondebosch, South Africa. 2 Division of Plant Sciences, University of Dundee at JHI, Invergowrie, Dundee DD2 5DA, UK 3 James Hutton Institute, EPI Division, Invergowrie, Dundee DD2 5DA, UK 4 Dept. of Seafood Science, National Kaohsiung Marine University, Kaohsiung City 811, Taiwan Presentation Title: Characterization of the cape floristic region rhizobia using 16S rRNA gene sequences and their distribution in different soil types Presentation Time: 1100 – 1120 67 2011
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INVENTING THE FUTURE IN INOCULANTS
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17 ICNF Organising Committee Graham
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