Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Similarities and differences of the volatile profiles of six spices explored by Proton Transfer Reaction Mass Spectrometry
Silvis, I.C.J. ; Luning, P.A. ; Klose, N. ; Jansen, M. ; Ruth, S.M. van - \ 2019
Food Chemistry 271 (2019). - ISSN 0308-8146 - p. 318 - 327.
2-Butanone (PubChem CID: 6569) - Acetic acid (PubChem CID: 176) - Aroma - Cinnamaldehyde (PubChem CID: 637511) - Estragole (PubChem CID: 8815) - Fingerprints - Methanol (PubChem CID: 887) - Non-destructive - P-cymene (PubChem CID: 7463) - PTR-TOFMS - Safranal (PubChem CID: 61041) - Volatile compounds

Aroma properties of spices are related to the volatile organic compounds (VOCs) present, which can provide distinct analytical signatures. The aim of the study was to examine similarity and diversity of VOC profiles of six common market spices (black/white pepper, chili paprika, cinnamon, nutmeg and saffron). The key volatiles were identified by PTR-TOFMS. Twelve samples per spice were subjected to PTR-Quadrupole MS (PTR-QMS) and Principal Component Analysis to compare the groups and examine diversity. With PTR-TOFMS, 101 volatile compounds were identified as total sum across all samples by mass and comparing them with literature data. Some spices comprised key character aroma compounds, e.g. cinnamaldehyde in cinnamon. For others, VOC groups, such as terpenes, acids and aldehydes topped the list. The PTR-QMS in combination with variables selection resulted in distinct PCA patterns for each spice. Variation within the spice groups was observed, but varied with the kind of spice. The results are valuable for future authentication studies.

Opbrengsttabellen Nederland 2018
Jansen, Hans ; Oosterbaan, Anne ; Mohren, G.M.J. ; Goudzwaard, L. ; Ouden, J. den; Schoonderwoerd, H. ; Thomassen, E.A.H. ; Schmidt, P. ; Copini, P. - \ 2018
Wageningen : Wageningen Academic Publishers - ISBN 9789086868766 - 172
In deze bundel zijn opbrengsttabellen van 15 boomsoorten opgenomen. In vergelijking met de tot nu toe geldende opbrengsttabellen uit 1996, bevat deze bundel meer soorten, meer dunningregimes, en zijn alle tabellen gebaseerd op Nederlandse meetgegevens. Voor 10 soorten zijn tabellen met zowel een matige als sterke dunning opgenomen. Voor de Japanse Lariks zijn twee regionale tabellen opgenomen. De populier heeft in deze bundel een tabel voor bomen in lijnbeplanting, naast de tabellen voor bos met diverse plantverbanden. Per soort is het rapport van de onderliggende studie weergegeven. Al deze studies volgden in grote lijnen de studie Groei en productie van douglas in Nederland. Becking's dunningproeven ontsloten. In vergelijking met de studies uit 1996, blijkt enerzijds de hoogtegroei per boniteit te verschillen (slechte boniteiten starten lager dan goede boniteiten, maar halen de groei later deels in). Anderzijds blijk de range tussen de beste en slechtste boniteit vaak ruimer dan in de eerdere studies.
Humanitarianism As Buffer : Displacement, aid and the politics of belonging in Abyei, Sudan/South Sudan
Jansen, Bram J. - \ 2018
African Affairs 117 (2018)468. - ISSN 0001-9909 - p. 370 - 391.

This article explores how the humanitarian presence and programs in the disputed border area of Abyei between Sudan and South Sudan can be understood as a buffer between conflicting parties, rather than as mere assistance to a displaced population. It aims to contribute to debates about the spatial impact of humanitarian governance and the politicization of aid in protracted crisis contexts, and specifically in relation to territorial disputes and border struggles. It is based on ethnographic fieldwork in South Sudan between 2011 and 2013. The article argues that the humanitarian response became part of the politics of belonging that lies at the heart of the dispute. The very acts of labelling, categorizing, and maintaining the subjects of aid are highly political, such as the creation of the category of the 'people of Abyei' in contrast to refugees or Internally Displaced People. As a result, the interventions have sustained governance over the territory and can be understood as a humanitarian buffer that may shape the border area of Abyei for many years to come.

Omics analyses of potato plant materials using an improved one-class classification tool to identify aberrant compositional profiles in risk assessment procedures
Kok, Esther ; Dijk, Jeroen van; Voorhuijzen, Marleen ; Staats, Martijn ; Slot, Martijn ; Lommen, Arjen ; Venema, Dini ; Pla, Maria ; Corujo, Maria ; Barros, Eugenia ; Hutten, Ronald ; Jansen, Jeroen ; Voet, Hilko van der - \ 2018
Food Chemistry (2018). - ISSN 0308-8146
Compositional analysis - Genetically modified organism - GMO - Omics profiling - Risk assessment

The objective of this study was to quantitatively assess potato omics profiles of new varieties for meaningful differences from analogous profiles of commercial varieties through the SIMCA one-class classification model. Analytical profiles of nine commercial potato varieties, eleven experimental potato varieties, one GM potato variety that had acquired Phytophtora resistance based on a single insert with potato-derived DNA sequences, and its non-GM commercial counterpart were generated. The ten conventional varieties were used to construct the one-class model. Omics profiles from experimental non-GM and GM varieties were assessed using the one-class SIMCA models. No potential unintended effects were identified in the case of the GM variety. The model showed that varieties that were genetically more distant from the commercial varieties were recognized as aberrant, highlighting its potential in determining whether additional evaluation is required for the risk assessment of materials produced from any breeding technique, including genetic modification.

Heruitgave Opbrengsttabellen Becking & de Vries Nederland 1959
Jansen, J.J. - \ 2018
Wageningen : Wageningen University & Research - 39 p.
Effecten van mosselkweek op sediment-dynamiek in de Waddenzee : uitgebreide samenvatting van het rapport “The effect of mussel farming on sedimentdynamics in the Wadden Sea - case studies evaluating the local effects of mussel seedfisheries and mussel harvest on turbidity and sedimentation”
Jansen, Henrice M. ; Capelle, Jacob J. - \ 2018
IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C047/18) - 67
The effect of mussel farming on sediment dynamics in the Wadden Sea : case studies evaluating the local effects of mussel seed fisheries and mussel harvest on turbidity and sedimentation
Jansen, Henrice M. ; Capelle, Jacob J. - \ 2018
IJmuiden : Wageningen Marine Research (Wageningen Marine Research report C046/18) - 67
Data from: Towards smarter harvesting from natural palm populations by sparing the individuals that contribute most to population growth or productivity
Jansen, M. ; Anten, N.P.R. ; Bongers, F. ; Martínez-Ramos, Miguel ; Zuidema, P.A. - \ 2018
Chamaedorea - forest management - harvest simulations - individual heterogenity - Integral Project Model - leaf harvesting - NFTP - sustainability - Chamaedorea elegans
1. Natural populations deliver a wide range of products that provide income for millions of people and need to be exploited sustainably. Large heterogeneity in individual performance within these exploited populations has the potential to improve population recovery after exploitation and thus help sustaining yields over time. 2. We explored the potential of using individual heterogeneity to design smarter harvest schemes, by sparing individuals that contribute most to future productivity and population growth, using the understorey palm Chamaedorea elegans as a model system. Leaves of this palm are an important non-timber forest product and long-term inter-individual growth variability can be evaluated from internode lengths. 3. We studied a population of 830 individuals, half of which was subjected to a 67 % defoliation treatment for three years. We measured effects of defoliation on vital rates and leaf size – a trait that determines marketability. We constructed integral projection models in which vital rates depended on stem length, past growth rate, and defoliation, and evaluated transient population dynamics to quantify population development and leaf yield. We then simulated scenarios in which we spared individuals that were either most important for population growth or had leaves smaller than marketable size. 4. Individuals varying in size or past growth rate responded similarly to leaf harvesting in terms of growth and reproduction. By contrast, defoliation-induced reduction in survival chance was smaller in large individuals than in small ones. Simulations showed that harvest-induced population decline was much reduced when individuals from size and past growth classes that contributed most to population growth were spared. Under this scenario cumulative leaf harvest over 20 years was somewhat reduced, but long-term leaf production was sustained. A three-fold increase in leaf yield was generated when individuals with small leaves are spared. 5. Synthesis and applications This study demonstrates the potential to create smarter systems of palm leaf harvest by accounting for individual heterogeneity within exploited populations. Sparing individuals that contribute most to population growth ensured sustained leaf production over time. The concepts and methods presented here are generally applicable to exploited plant and animal species which exhibit considerable individual heterogeneity.
Thought for urban food planning : The Oosterwold (NL) experiment to normalise agriculture in urban planning
Jansma, J.E. ; Janssen-Jansen, L. ; Valk, A.J.J. van der; Wertheim-Heck, S.C.O. - \ 2018
In: Proceedings of Annual AESOP congress 10-14 July 2018, Gothenburg - p. 10 - 13.
Proceedings of Annual AESOP congress 10-14 Juli 2018, Gothenburg
Increasing quality of life in pulmonary arterial hypertension : is there a role for nutrition?
Vinke, Paulien ; Jansen, Suzanne M. ; Witkamp, Renger F. ; Norren, Klaske van - \ 2018
Heart Failure Reviews 23 (2018)5. - ISSN 1382-4147 - p. 711 - 722.
Deficiencies - Exercise - Lifestyle - Nutrition - Pulmonary arterial hypertension - Review

Pulmonary arterial hypertension (PAH) is a progressive disease primarily affecting the pulmonary vasculature and heart. PAH patients suffer from exercise intolerance and fatigue, negatively affecting their quality of life. This review summarizes current insights in the pathophysiological mechanisms underlying PAH. It zooms in on the potential involvement of nutritional status and micronutrient deficiencies on PAH exercise intolerance and fatigue, also summarizing the potential benefits of exercise and nutritional interventions. Pubmed/Medline, Scopus, and Web of Science were searched for publications on pathophysiological mechanisms of PAH negatively affecting physical activity potential and nutritional status, and for potential effects of interventions involving exercise or nutritional measures known to improve exercise intolerance. Pathophysiological processes that contribute to exercise intolerance and impaired quality of life of PAH patients include right ventricular dysfunction, inflammation, skeletal muscle alterations, and dysfunctional energy metabolism. PAH-related nutritional deficiencies and metabolic alterations have been linked to fatigue, exercise intolerance, and endothelial dysfunction. Available evidence suggests that exercise interventions can be effective in PAH patients to improve exercise tolerance and decrease fatigue. By contrast, knowledge on the prevalence of micronutrient deficiencies and the possible effects of nutritional interventions in PAH patients is limited. Although data on nutritional status and micronutrient deficiencies in PAH are scarce, the available knowledge, including that from adjacent fields, suggests that nutritional intervention to correct deficiencies and metabolic alterations may contribute to a reduction of disease burden.

Groei en productie van zwarte els in Nederland
Jansen, J.J. ; Oosterbaan, A. ; Mohren, G.M.J. ; Copini, P. ; Ouden, J. den - \ 2018
Wageningen : Wageningen University & Research (FEM Groei en Productie rapport 2018-10) - 47
In the Netherlands growth and yield research on black alder was done on a limited scale from 1965 to 1990. This regards two studies by the Dorschkamp/IBN research institute; together with the permanent sample plots from the timber prognosis system HOSP, this comprises a dataset of 14 plots with 59 recordings. In addition, the information from 518 stands of the Fourth National Forest Inventory was used. For the development of top height htop with age t Jansen’s et al. polymorphic model with site index h50 and four additional parameters fitted best. The diameter at a height of 7 m (d7) was estimated from data of the Fourth National Forest Inven-tory. The diameter development up to stand height of 7 m was described with a model of Jansen et al., a power function in htop and the estimated value for d7. From a stand height of 7 m upwards, the basal area increment (iG) was also described by Jansen’s et al. model based on a power function with t, year of recording (yor), and the stand density of Hart (S %). For S% > 15.7 the basal area increment decreases non-linear with increasing S %. The model contains a correction factor for yor, although this was not significant, as the year of recording (yor), turned out to be not significant. The effect of thinning on the diameter after thinning was modelled with the La Bastide-Faber model. The models were used to construct a yield table with five site classes and one thinning intensity.
Modelling the distribution and compositional variation of plant communities at the continental scale
Jiménez-Alfaro, Borja ; Suárez-Seoane, Susana ; Chytrý, Milan ; Hennekens, Stephan M. ; Willner, Wolfgang ; Hájek, Michal ; Agrillo, Emiliano ; Álvarez-Martínez, Jose M. ; Bergamini, Ariel ; Brisse, Henry ; Brunet, Jörg ; Casella, Laura ; Dítě, Daniel ; Font, Xavier ; Gillet, François ; Hájková, Petra ; Jansen, Florian ; Jandt, Ute ; Kącki, Zygmunt ; Lenoir, Jonathan ; Rodwell, John S. ; Schaminée, Joop H.J. ; Sekulová, Lucia ; Šibík, Jozef ; Škvorc, Željko ; Tsiripidis, Ioannis - \ 2018
Diversity and Distributions 24 (2018)7. - ISSN 1366-9516 - p. 978 - 990.
community distribution models - ecosystem properties - extent of occurrence - generalized dissimilarity modelling - habitat conservation - plant communities - vegetation
Aim: We investigate whether (1) environmental predictors allow to delineate the distribution of discrete community types at the continental scale and (2) how data completeness influences model generalization in relation to the compositional variation of the modelled entities. Location: Europe. Methods: We used comprehensive datasets of two community types of conservation concern in Europe: acidophilous beech forests and base-rich fens. We computed community distribution models (CDMs) calibrated with environmental predictors to predict the occurrence of both community types, evaluating geographical transferability, interpolation and extrapolation under different scenarios of sampling bias. We used generalized dissimilarity modelling (GDM) to assess the role of geographical and environmental drivers in compositional variation within the predicted distributions. Results: For the two community types, CDMs computed for the whole study area provided good performance when evaluated by random cross-validation and external validation. Geographical transferability provided lower but relatively good performance, while model extrapolation performed poorly when compared with interpolation. Generalized dissimilarity modelling showed a predominant effect of geographical distance on compositional variation, complemented with the environmental predictors that also influenced habitat suitability. Main conclusions: Correlative approaches typically used for modelling the distribution of individual species are also useful for delineating the potential area of occupancy of community types at the continental scale, when using consistent definitions of the modelled entity and high data completeness. The combination of CDMs with GDM further improves the understanding of diversity patterns of plant communities, providing spatially explicit information for mapping vegetation diversity and related habitat types at large scales.
Supplementation of fructooligosaccharides to suckling piglets affects intestinal microbiota colonization and immune development
Schokker, Dirkjan ; Fledderus, Jan ; Jansen, Rutger ; Vastenhouw, Stephanie A. ; Bree, Freddy M. de; Smits, Mari A. ; Jansman, Alfons A.J.M. - \ 2018
Journal of Animal Science 96 (2018)6. - ISSN 0021-8812 - p. 2139 - 2153.
Emerging knowledge shows the importance of early life events in programming the intestinal mucosal immune system and development of the intestinal barrier function. These processes depend heavily on close interactions between gut microbiota and host cells in the intestinal mucosa. In turn, development of the intestinal microbiota is largely dependent on available nutrients required for the specific microbial community structures to expand. It is currently not known what the specificities are of intestinal microbial community structures in relation to the programming of the intestinal mucosal immune system and development of the intestinal barrier function. The objective of the present study was to investigate the effects of a nutritional intervention on intestinal development of suckling piglets by daily oral administration of fructooligosaccharides (FOS) over a period of 12 d (days 2–14 of age). At the microbiota community level, a clear “bifidogenic” effect of the FOS administration was observed in the colon digesta at day 14. The former, however, did not translate into significant changes of local gene expression in the colonic mucosa. In the jejunum, significant changes were observed for microbiota composition at day 14, and microbiota diversity at day 25. In addition, significant differentially expressed gene sets in mucosal tissues of the jejunum were identified at both days 14 and 25 of age. At the age of 14 d, a lower activity of cell cycle–related processes and a higher activity of extracellular matrix processes were observed in the jejunal mucosa of piglets supplemented with FOS compared with control piglets. At day 25, the lower activity of immune-related processes in jejunal tissue was seen in piglets supplemented with FOS. Villi height and crypt depth in the jejunum were significantly different at day 25 between the experimental and control groups, where piglets supplemented with FOS had greater villi and deeper crypts. We conclude that oral FOS administration during the early suckling period of piglets had significant bifidogenic effects on the microbiota in the colon and on gene expression in the jejunal mucosa by thus far unknown mechanisms.
High adiposity is associated with higher nocturnal and diurnal glycaemia, but not with glycemic variability in older individuals without diabetes
Noordam, Raymond ; Huurman, Neline C. ; Wijsman, Carolien A. ; Akintola, Abimbola A. ; Jansen, Steffy W.M. ; Stassen, Stephanie ; Beekman, Marian ; Rest, Ondine van de; Slagboom, P.E. ; Mooijaart, Simon P. ; Heemst, Diana van - \ 2018
Frontiers in Endocrinology 9 (2018).
Adiposity - Body composition - Continuous glucose monitoring - Glycemia - Glycemic variability

Background: It is well known that adiposity is a risk factor for insulin resistance and type 2 diabetes mellitus. In the present study, we aimed to investigate the associations of measures of adiposity with indices of glycemia and of glycemic variability over a 72-h period in non-diabetic older adults. Methods: This cross-sectional study was conducted in non-diabetic individuals from the Active and Healthy Aging Study (N = 228), Switchbox (N = 116), and the Growing Old Together Study (N = 94). Body mass index (BMI) and waist circumference were measured, and indices of glycemia and glycemic variability were derived from continuous glucose monitoring (CGM) using the Mini-Med® CGM system. Associations between adiposity and CGM were studied separately for the three cohorts, and derived estimates were subsequently meta-analyzed. Results: After meta-analyzing the results from the separate cohorts, individuals with a higher BMI had higher levels of glycemia. Individuals with BMI between 30 and 35 kg/m2 had 0.28 mmol/L [95% confidence interval (CI): 0.12-0.44] higher 72 h-mean glucose concentration, 0.26 mmol/L (0.10-0.42) higher diurnal glucose (6:00 a.m. to 0:00 a.m.), and 0.39 mmol/L (0.19; 0.59) higher nocturnal glucose (3:00 a.m. to 6:00 a.m.) than participants with a normal weight (BMI 18.5-25 kg/m2). However, no associations were observed between higher BMI and glycemic variability. Results for glycemia and glycemic variability were similarly observed for a high waist circumference. Conclusion: High adiposity associates with constant higher mean glucose levels over the day in non-diabetic older adults.

The persistence of a broad range of antibiotics during calve, pig and broiler manure storage
Berendsen, B.J.A. ; Lahr, J. ; Nibbeling, C. ; Jansen, L.J.M. ; Bongers, I.E.A. ; Wipfler, E.L. ; Schans, M.G.M. van de - \ 2018
Chemosphere 204 (2018). - ISSN 0045-6535 - p. 267 - 276.
Antibiotics - Dissipation - Environment - Fate - Manure - Persistence - Reviewer suggestions

After administration to livestock, a large fraction of antibiotics are excreted unchanged via excreta and can be transferred to agricultural land. For effective risk assessment a critical factor is to determine which antibiotics can be expected in the different environmental compartments. After excretion, the first relevant compartment is manure storage. In the current study, the fate of a broad scope of antibiotics (n = 46) during manure storage of different livestock animals (calves, pigs, broilers) was investigated. Manure samples were fortified with antibiotics and incubated during 24 days. Analysis was carried out by LC-MS. The dissipation of the antibiotics was modelled based on the recommendations of FOCUS working group. Sulphonamides relatively quickly dissipate in all manure types, with a DT90 of in general between 0.2 and 30 days. Tetracyclines (DT90 up to 422 days), quinolones (DT90 100–5800 days), macrolides (DT90 18–1000 days), lincosamides (DT90 135–1400 days) and pleuromutilins (DT90 of 49–1100 days) are in general much more persistent, but rates depend on the manure type. Specifically lincomycin, pirlimycin, tiamulin and most quinolones are very persistent in manure with more than 10% of the native compound remaining after a year in most manure types. For all compounds tested in the sub-set, except the macrolides, the dissipation was an abiotic process. Based on the persistence and current frequency of use, oxytetracycline, doxycycline, flumequine and tilmicosin can be expected to end up in environmental compartments. Ecotoxicological data should be used to further prioritize these compounds.

Bouwen aan vertrouwen: woningbouwprogrammering aan de vooravond van de omgevingswet : eindrapport PROSPER-onderzoek
Wichard, Lars ; Janssen-Jansen, Leonie ; Spit, Tejo - \ 2018
Wageningen : Wageningen Universiteit, Land Use Planning - ISBN 9789463432696 - 79
Databewakers: We moeten niet naïef zijn
Vernede, Raoul ; Brouwer, Maarten ; Jansen, Bert ; Knibbe, Willem Jan - \ 2018
Effects of wild ungulates on the regeneration, structure and functioning of temperate forests: A semi-quantitative review
Ramirez Chiriboga, J.I. ; Jansen, P.A. ; Poorter, L. - \ 2018
Forest Ecology and Management 424 (2018). - ISSN 0378-1127 - p. 406 - 419.
Wild ungulates such as red deer, roe deer and wild boar are key drivers of forest ecosystems. Across the northern hemisphere, their range and abundance is increasing, while at the same time forest conversion and habitat fragmentation have led to a large variation in ungulate density and composition among areas. Understanding ungulate density impacts are important in order to prevent shifts towards undesired states, such as from forest to heathland. Here, we assess the effects of ungulate density on forest regeneration, development and functioning. We carried out a systematic literature review of 433 published studies in temperate forests, and used the data to model dose-response curves of the effects of ungulate density on three sets of forest attributes; tree regeneration (abundance, species richness and composition), forest structure (horizontal and vertical), and forest functioning (nutrient cycling in soil, timber and food production). Ungulate density averaged 23.6 km−2 across studies. Ungulates had a negative effect on forest regeneration, structure and functioning in 70% of the evaluated cases. The dose-response curves had a sigmoidal, rather than a unimodal shape. Critical tipping points, where ungulates started to have a negative effect on forest regeneration, were found at an ungulate metabolic weight density of 115 kg km−2 for forest regeneration, 141 kg km−2 for forest structure, and 251 kg km−2 for forest functioning, which is roughly equivalent to 10, 13 and 23 roe deer per km−2. Forest regeneration was most sensitive to immediate browsing and trampling impacts of small seedlings, while forest functioning was least sensitive because of time lags. However, these effects may build up over time. We suggest research priorities for studying ungulate-plant interactions in temperate forests, and make management recommendations how to balance wildlife with a functioning forest.
Provenance, Ideology and the Public Interest in Planning
Janssen-Jansen, Leonie ; Lloyd, Greg - \ 2018
In: The Routledge Handbook of Institutions and Planning in Action / Salet, Willem, Routledge - ISBN 9781138085732
Comparative genomics of the nonlegume Parasponia reveals insights into evolution of nitrogen-fixing rhizobium symbioses
Velzen, R. van; Holmer, R. ; Bu, F. ; Rutten, L.J.J. ; Zeijl, A.L. van; Liu, W. ; Santuari, L. ; Cao, Q. ; Sharma, Trupti ; Shen, Defeng ; Purwana Roswanjaya, Yuda ; Wardhani, T. ; Seifi Kalhor, M. ; Jansen, Joelle ; Hoogen, D.J. van den; Güngör, Berivan ; Hartog, M.V. ; Hontelez, J. ; Verver, Jan ; Yang, Wei-Cai ; Schijlen, E.G.W.M. ; Repin, Rimi ; Schilthuizen, M. ; Schranz, M.E. ; Heidstra, R. ; Miyata, Kana ; Fedorova, E. ; Kohlen, W. ; Bisseling, A.H.J. ; Smit, S. ; Geurts, R. - \ 2018
Proceedings of the National Academy of Sciences of the United States of America 115 (2018)20. - ISSN 0027-8424 - p. E4700 - E4709.
Nodules harboring nitrogen-fixing rhizobia are a well-known trait of legumes, but nodules also occur in other plant lineages, with rhizobia or the actinomycete Frankia as microsymbiont. It is generally assumed that nodulation evolved independently multiple times. However, molecular-genetic support for this hypothesis is lacking, as the genetic changes underlying nodule evolution remain elusive. We conducted genetic and comparative genomics studies by using Parasponia species (Cannabaceae), the only nonlegumes that can establish nitrogen-fixing nodules with rhizobium. Intergeneric crosses between Parasponia andersonii and its nonnodulating relative Trema tomentosa demonstrated that nodule organogenesis, but not intracellular infection, is a dominant genetic trait. Comparative transcriptomics of P. andersonii and the legume Medicago truncatula revealed utilization of at least 290 orthologous symbiosis genes in nodules. Among these are key genes that, in legumes, are essential for nodulation, including NODULE INCEPTION (NIN) and RHIZOBIUM-DIRECTED POLAR GROWTH (RPG). Comparative analysis of genomes from three Parasponia species and related nonnodulating plant species show evidence of parallel loss in nonnodulating species of putative orthologs of NIN, RPG, and NOD FACTOR PERCEPTION. Parallel loss of these symbiosis genes indicates that these nonnodulating lineages lost the potential to nodulate. Taken together, our results challenge the view that nodulation evolved in parallel and raises the possibility that nodulation originated ∼100 Mya in a common ancestor of all nodulating plant species, but was subsequently lost in many descendant lineages. This will have profound implications for translational approaches aimed at engineering nitrogen-fixing nodules in crop plants.
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