Hannes Andres Gamper

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Gamper

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Hannes Andres

ORCID

0000-0002-8185-3472

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Publications1 - 5 of 5

Geographical patterns of root nodule bacterial diversity in cultivated and wild populations of a woody legume crop
Ramoneda, Josep; Le Roux, Johannes J.; Frossard, Emmanuel; et al. (2020)
FEMS Microbiology Ecology
There is interest in understanding how cultivation, plant genotype, climate and soil conditions influence the biogeography of root nodule bacterial communities of legumes. For crops from regions with relict wild populations, this is of even greater interest because the effects of cultivation on symbiont communities can be revealed, which is of particular interest for bacteria such as rhizobia. Here, we determined the structure of root nodule bacterial communities of rooibos (Aspalathus linearis), a leguminous shrub endemic to South Africa. We related the community dissimilarities of the root nodule bacteria of 18 paired cultivated and wild rooibos populations to pairwise geographical distances, plant ecophysiological characteristics and soil physicochemical parameters. Using next-generation sequencing data, we identified region-, cultivation- and farm-specific operational taxonomic units for four distinct classes of root nodule bacterial communities, dominated by members of the genus Mesorhizobium. We found that while bacterial richness was locally increased by organic cultivation, strong biogeographical differentiation in the bacterial communities of wild rooibos disappeared with cultivation of one single cultivar across its entire cultivation range. This implies that expanding rooibos farming has the potential to endanger wild rooibos populations through the homogenisation of root nodule bacterial diversity. © FEMS 2020.
Lessons from invasion biology: Can eco-evolutionary experience sustain benefits from mycorrhizal fungi and rhizobia in plant production?
Ramoneda, Josep; Le Roux, Johannes; Frossard, Emmanuel; et al. (2019)
AoB Plants
Mutualistic plant–microbial functioning relies on co-adapted symbiotic partners as well as conducive environmental conditions. Choosing particular plant genotypes for domestication and subsequent cultivar selection can narrow the gene pools of crop plants to a degree that they are no longer able to benefit from microbial mutualists. Elevated mineral nutrient levels in cultivated soils also reduce the dependence of crops on nutritional support by mutualists such as mycorrhizal fungi and rhizobia. Thus, current ways of crop production are predestined to compromise the propagation and function of microbial symbionts, limiting their long-term benefits for plant yield stability. The influence of mutualists on non-native plant establishment and spread, i.e. biological invasions, provides an unexplored analogue to contemporary crop production that accounts for mutualistic services from symbionts like rhizobia and mycorrhizae. The historical exposure of organisms to biotic interactions over evolutionary timescales, or so-called eco-evolutionary experience (EEE), has been used to explain the success of such invasions. In this paper, we stress that consideration of the EEE concept can shed light on how to overcome the loss of microbial mutualist functions following crop domestication and breeding. We propose specific experimental approaches to utilize the wild ancestors of crops to determine whether crop domestication compromised the benefits derived from root microbial symbioses or not. This can predict the potential for success of mutualistic symbiosis manipulation in modern crops and the maintenance of effective microbial mutualisms over the long term.
Soil microbial community coalescence and fertilization interact to drive the functioning of the legume-rhizobium symbiosis
Ramoneda, Josep; Le Roux, Johannes; Stadelmann, Stefanie; et al. (2021)
Journal of Applied Ecology
1. Soil microbial community coalescence, where entire microbial communities mix and interact under new conditions, is a widespread phenomenon whose applicability for targeted root microbiome assembly has not been studied. Whether soil mixing can lead to predictable outcomes for community assembly and functioning of specific functional groups, for example, N2-fixing rhizobia, remains unknown. 2. Using a legume shrub adapted to nutrient-poor soils, we tested the effects of community coalescence on plant nutrition and growth, and its influence on the rhizobial root nodule symbiosis. We grew seedlings of rooibos [Aspalathus linearis (Burm.f.) Dahlg.] in individual rhizosphere soils collected from cultivated and wild rooibos plants and their mixtures, and included a fertilization treatment. Portions of the taxonomic gyrB and the symbiotic nodA gene makers were sequenced to characterize rhizobial communities present in rooibos root nodules under the different soil conditions. 3. Overall, community coalescence by soil mixing had positive effects on plant nutrition and growth, and interacted with fertilizer addition to concurrently change rhizobial taxonomic evenness and promote higher relative N2 fixation. We identified particular rhizobia preferentially associated with rooibos plants that showed higher N fractions from N2 fixation, raised in mixed fertilized soils. 4. These findings indicate that soil bacterial community coalescence and fertilization can have synergistic effects on plant performance, while promoting the assembly of alternative symbiotic rhizobial communities that provide improved nutritional benefits to host plants. 5. Synthesis and applications. The combination of soil mixing and fertilizer addition may be an important, but hitherto overlooked measure to improve the functioning of rhizobium symbioses in legume crops. Microbial community coalescence should gain recognition as a potentially effective mechanism to improve the functioning of plant microbiomes.
Mycorrhizal fungi-mediated uptake of tree-derived nutrients by crops – the role of tree-maintained versus crop-associated fungal mycelia
Dierks, Janina; Gamper, Hannes Andres; Blaser-Hart, Wilma J.; et al. (2024)
Soil Biology and Biochemistry
Arbuscular mycorrhizal (AM) fungi translocate nutrients within agroforestry systems but the role of common mycorrhizal fungal networks (CMNs) is unclear. We compared AM fungi-mediated nutrient transfer from mango versus faidherbia trees to maize plants to understand how to foster the AM symbiosis for enhanced agroecosystem sustainability. In mesocosms we applied 15N and 33P tracers via tree stem injection or root-free soil labeling compartments to test tree-to-maize versus soil-to-maize nutrient transfer via AM fungi. Maize plants grew in large in-growth cores with intact versus broken mycelia. Soil-to-maize transfer was assessed with and without trees to compare nutrient transfer via tree-maintained AM fungi i.e. CMNs versus maize-associated AM fungi. Tracer application via stem injection neither corroborated nor falsified our hypothesis of tree-to-maize nitrogen and phosphorus transfer. Soil-to-maize nutrient transfer occurred but was not enhanced by the presence of mango or faidherbia trees. Competition with maize plants for nitrogen but not phosphorus was greater with mango than faidherbia trees. Results from our experimental set-up provide neither evidence nor disproval for CMNs between two-year-old trees and ten-week-old maize plants. In the absence of trees and tree-maintained AM fungal mycelia maize plants developed their own AM fungal mycelia that mediated uptake of nutrients from beyond the maize plants’ rooting zones.
The rooibos symbiotic root microbiome: does increased rhizobial and arbuscular mycorrhyzal fungal (AMF) diversity improve plant performance?
Ramoneda, Josep; Gamper, Hannes Andres; Frey, Beat; et al. (2018)

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