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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Patterns of Transmission Ratio Distortion in Interspecific Lettuce Hybrids Reveal a Seks Independent Gametophytic Barrier
Giesbers, A.K.J. ; Boer, E. den; Ulen, Jacqueline ; Kaauwen, M.P.W. van; Visser, R.G.F. ; Niks, R.E. ; Jeuken, M.J.W. - \ 2019
Genetics 211 (2019)1. - ISSN 0016-6731 - p. 263 - 276.
Interspecific crosses can result in progeny with reduced vitality or fertility due to genetic incompatibilities between species, a phenomenon known as hybrid incompatibility (HI). HI is often caused by a bias against deleterious allele combinations, which results in transmission ratio distortion (TRD). Here, we determined the genome-wide distribution of HI between wild lettuce, Lactuca saligna, and cultivated lettuce, L. sativa, in a set of backcross inbred lines (BILs) with single introgression segments from L. saligna introgressed into a L. sativa genetic background. Almost all BILs contained an introgression segment in a homozygous state except a few BILs, for which we were able to obtain only a single heterozygous introgression. Their inbred progenies displayed severe TRD with a bias toward the L. sativa allele and complete nontransmission of the homozygous L. saligna introgression, i.e., absolute HI. These HI might be caused by deleterious heterospecific allele combinations at two loci. We used an multilocus segregating interspecific F2 population to identify candidate conspecific loci that can nullify the HI in BILs. Segregation analysis of developed double-introgression progenies showed nullification of three HI and proved that these HI are explained by nuclear pairwise incompatibilities. One of these digenic HI showed 29% reduced seed set and its pattern of TRD pointed to a sex-independent gametophytic barrier. Namely, this HI was caused by complete nontransmission of one heterospecific allele combination at the haploid stage, surprisingly in both male and female gametophytes. Our study shows that two-locus incompatibility systems contribute to reproductive barriers among Lactuca species.
Brief communication: Strengthening coherence between climate change adaptation and disaster risk reduction
Mysiak, J. ; Castellari, Sergio ; Kurnik, Blaz ; Swart, R.J. ; Pringle, Patrick ; Schwarzenbach, R. ; Wolters, H. ; Jeuken, A. ; Linden, Paul van der - \ 2018
Natural Hazards and Earth System Sciences 18 (2018)11. - ISSN 1561-8633 - p. 3137 - 3143.
Reducing disaster risks and adapting to climate change are ever more important policy goals in Europe and worldwide. The commitment to the 2030 Agenda for Sustainable Development and complementary multilateral frameworks, including the Sendai Framework for Disaster Risk Reduction 2015-2030 and the Paris Agreement on Climate Change, has galvanised pursuits for policy coherence. The report »Climate change adaptation and disaster risk reduction in Europe: enhancing coherence of the knowledge base, policies and practices« of the European Environment Agency identified several ways how coherence and resilience can be built through knowledge sharing, collaboration and investments.
Bidirectional backcrosses between wild and cultivated lettuce identify loci involved in nonhost resistance to downy mildew
Giesbers, Anne K.J. ; Boer, Erik Den; Braspenning, David N.J. ; Bouten, Thijs P.H. ; Specken, Johan W. ; Kaauwen, Martijn P.W. van; Visser, Richard G.F. ; Niks, Rients E. ; Jeuken, Marieke J.W. - \ 2018
Theoretical and Applied Genetics 131 (2018)8. - ISSN 0040-5752 - p. 1761 - 1776.

Key message: The nonhost resistance of wild lettuce to lettuce downy mildew seems explained by four components of a putative set of epistatic genes. Abstract: The commonplace observation that plants are immune to most potential pathogens is known as nonhost resistance (NHR). The genetic basis of NHR is poorly understood. Inheritance studies of NHR require crosses of nonhost species with a host, but these crosses are usually unsuccessful. The plant-pathosystem of lettuce and downy mildew, Bremia lactucae, provides a rare opportunity to study the inheritance of NHR, because the nonhost wild lettuce species Lactuca saligna is sufficiently cross-compatible with the cultivated host Lactuca sativa. Our previous studies on NHR in one L. saligna accession led to the hypothesis that multi-locus epistatic interactions might explain NHR. Here, we studied NHR at the species level in nine accessions. Besides the commonly used approach of studying a target trait from a wild donor species in a cultivar genetic background, we also explored the opposite, complementary approach of cultivar introgression in a wild species background. This bidirectional approach encompassed (1) nonhost into host introgression: identification of L. saligna derived chromosome regions that were overrepresented in highly resistant BC1 plants (F1 × L. sativa), (2) host into nonhost introgression: identification of L. sativa derived chromosome regions that were overrepresented in BC1 inbred lines (F1 × L. saligna) with relatively high infection levels. We demonstrated that NHR is based on resistance factors from L. saligna and the genetic dose for NHR differs between accessions. NHR seemed explained by combinations of epistatic genes on three or four chromosome segments, of which one chromosome segment was validated by the host into nonhost approach.

Nonhost wild lettuce as a donor for resistance to downy mildew in cultivated lettuce
Giesbers, Anne K.J. - \ 2018
Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Marieke Jeuken; Rients Niks. - Wageningen : Wageningen University - ISBN 9789463438797 - 147
Regioscan Zoetwatermaatregelen : beperken watervraag landbouw door kleinschalige maatregelen
Delsman, J.R. ; Reinhard, A.J. ; Winkel, T. te; Loon, A.H. van; Boekel, E.M.P.M. van; Bartholomeus, R.P. ; Massop, H.T.L. ; Mulder, H.M. ; Polman, N.B.P. ; Schasfoort, F.E. ; Jeuken, A.B.M. - \ 2018
Landschap : tijdschrift voor Landschapsecologie en Milieukunde 2018 (2018)1. - ISSN 0169-6300 - p. 66 - 73.
Omdat zoetwatertekorten steeds talrijker worden, zoeken waterbeheerders met landbouwers naar manieren om de vraag te verminderen. Onbekend is in hoeverre kleinschalige maatregelen kunnen bijdragen aan de regionale zoetwateropgave en tegen welke kosten. De Regioscan Zoetwatermaatregelen geeft ruimtelijk inzicht in de rendabiliteit van maatregelen voor agrariërs, en effecten op gebiedsniveau. Het instrument ondersteunt hiermee de dialoog tussen waterbeheerder en boer. Vooralsnog lijken baten van kleinschalige zoetwatermaatregelen alleen in specifieke gebieden op te wegen tegen de kosten.
GrassVESS: a modification of the visual evaluation of soil structure method for grasslands
Emmet-Booth, J.P. ; Bondi, G. ; Fenton, O. ; Forristal, P.D. ; Jeuken, E. ; Creamer, R.E. ; Holden, N.M. - \ 2018
Soil Use and Management 34 (2018)1. - ISSN 0266-0032 - p. 37 - 47.
grassland soil quality - root-mat evaluation - soil structure - Sustainable soil management - visual soil evaluation
Visual evaluation of soil structure (VESS) is used for assessing arable management impact on soil quality. When used on pastures, operators have identified limitations because VESS does not consider a surface root-mat typical of managed grassland. The structure of the root-mat may be indicative of nutrient use efficiency, pollution potential and subsurface compaction. The objectives of this research were to develop GrassVESS for grassland soil management, to compare it with VESS and quantitative physical indicators and to assess its utility for soil management. GrassVESS maintained the methodological strengths of VESS, but uses a flow chart, grassland images and a new root-mat score. A focus group found GrassVESS to be quicker, dealt better with technical information and made root-mat evaluation easier. The range of structural quality scores assigned by the focus group for a site was less for GrassVESS than VESS, suggesting the procedure is more reproducible, thus suitable for use by a range of stakeholders. GrassVESS was also deployed at 30 grassland sites across Ireland. Results indicated that GrassVESS generated the same overall diagnoses as VESS, but the GrassVESS root-mat structural quality score was better related to bulk density, total porosity at 5–10 cm and a visual estimation of damaged sward area. It was concluded that GrassVESS has improved the VESS method for the specific assessment of grassland soil structural quality and could be used in real-time farm management decision support.
Effector-mediated discovery of a novel resistance gene against Bremia Lactucae in a nonhost lettuce species
Giesbers, A.K.J. ; Pelgrom, Alexandra ; Visser, R.G.F. ; Niks, R.E. ; Ackerveken, Guido Van Den; Jeuken, M.J.W. - \ 2017
New Phytologist 216 (2017)3. - ISSN 0028-646X - p. 915 - 926.
Candidate effectors from lettuce downy mildew (Bremia lactucae) enable high-throughput germplasm screening for the presence of resistance (R) genes. The nonhost species Lactuca saligna comprises a source of B. lactucae R genes that has hardly been exploited in lettuce breeding. Its cross-compatibility with the host species L. sativa enables the study of inheritance of nonhost resistance (NHR). We performed transient expression of candidate RXLR effector genes from B. lactucae in a diverse Lactuca germplasm set. Responses to two candidate effectors (BLR31 and BLN08) were genetically mapped and tested for co-segregation with disease resistance. BLN08 induced a hypersensitive response (HR) in 55% of the L. saligna accessions, but responsiveness did not co-segregate with resistance to Bl:24. BLR31 triggered an HR in 5% of the L. saligna accessions, and revealed a novel R gene providing complete B. lactucae race Bl:24 resistance. Resistant hybrid plants that were BLR31 nonresponsive indicated other unlinked R genes and/or nonhost QTLs. We have identified a candidate avirulence effector of B. lactucae (BLR31) and its cognate R gene in L. saligna. Concurrently, our results suggest that R genes are not required for NHR of L. saligna.
VPRO Tegenlicht: Tijdperk van de mens : Hoe de mens in het Antropoceen zelf verantwoordelijkheid kan nemen
Jeuken, M.J.W. - \ 2017
Adaptation pathways in planning for uncertain climate change : Applications in Portugal, the Czech Republic and the Netherlands
Zandvoort, Mark ; Campos, Inês S. ; Vizinho, André ; Penha-Lopes, Gil ; Lorencová, Eliška Krkoška ; Brugge, Rutger van der; Vlist, Maarten J. van der; Brink, Adri van den; Jeuken, Ad B.M. - \ 2017
Environmental Science & Policy 78 (2017). - ISSN 1462-9011 - p. 18 - 26.
Adaptation pathways - Climate adaptation - Design choices - Planning tools - Policy-making - Uncertainty

Adaptation pathways are developed to design adaptive policies to handle climate change uncertainty. Use of this tool varies across planning practices and adaptation challenges and adjusting the tool to particular practices can foster its adequate use. To gain insight into the use of adaptation pathways, we compared four initiatives (one each in Portugal and the Czech Republic and two in the Netherlands) with regard to design choices made. We found six design choices which need to be considered when adjusting adaptation pathways. Design choices about the geographic scale, inclusion of sectors, the generation and delineation of adaptation options, specification of possible pathways, the related performance metrics and the type of assessment are interdependent, but they are also influenced by contextual aspects. Analysis of the institutional diversity, planning culture and framing shows that the use of adaptation pathways is flexible enough to be adjusted for diverging planning practices. However, the tool is best suited to deliver local adaptation solutions, and adequate use depends on consensus about the adaptation problem, setting objective thresholds and determining uncertainty about future change. We conclude that understanding the customised use of tools for local planning practices is essential for adaptive policy design.

How Regime Shifts in Connected Aquatic Ecosystems Are Affected by the Typical Downstream Increase of Water Flow
Gerven, Luuk P.A. Van; Kuiper, Jan J. ; Janse, Jan H. ; Janssen, Annette B.G. ; Jeuken, Michel ; Mooij, Wolf M. ; Klein, Jeroen J.M. De - \ 2016
Ecosystems 20 (2016)4. - ISSN 1432-9840 - p. 733 - 744.
All over the world freshwater ecosystems like ponds, ditches and lakes suffer from nutrient-driven regime shifts from submerged plants to dominance by algae or free-floating plants. Although freshwaters are often connected and part of a network, most of our current knowledge on regime shifts comes from studies of isolated ecosystems. The few studies that have assessed the spatial manifestation of regime shifts overlooked the hydrological fact that the water flow through connected waters typically increases in the downstream direction. Here, we use a complex ecosystem model to show that this increase in flow does not lead to spatial differences in ecosystem state. We support these findings with a simple, analytically tractable, nutrient retention model on connected waterbodies. The model shows that all bodies have the same nutrient concentration despite spatial gradients in the flow of water as well as nutrients carried by the water. As a consequence, each connected waterbody is equally vulnerable to a regime shift, implying a regime shift to be system-wide. Furthermore, it appeared that each connected waterbody behaves the same as an isolated waterbody, implying that the vast body of theory on isolated systems, like alternative stable states theory, can still be useful for connected systems. Although these findings are violated when there is heterogeneity in lateral runoff or waterbody characteristics—leading to spatial differences in ecosystem state and therefore to differences in the vulnerability to a regime shift—they show that the typical downstream build-up of water flow does not necessarily lead to differences in ecological state, and thereby provide a basic concept to better understand the ecology of connected freshwaters.
Rationalization of genes for resistance to Bremia lactucae in lettuce
Parra, Lorena ; Maisonneuve, Brigitte ; Lebeda, Ales ; Schut, Johan ; Christopoulou, Marilena ; Jeuken, Marieke ; McHale, Leah ; Truco, Maria Jose ; Crute, Ian ; Michelmore, Richard - \ 2016
Euphytica 210 (2016)3. - ISSN 0014-2336 - p. 309 - 326.
Dm gene - Lactuca spp. - Lettuce downy mildew - Plant breeding - Quantitative trait locus - Resistance genes

Lettuce downy mildew caused by Bremia lactucae is the most important disease of lettuce worldwide. Breeding for resistance to this disease is a major priority for most lettuce breeding programs. Many genes and factors for resistance to B. lactucae have been reported by multiple researchers over the past ~50 years. Their nomenclature has not been coordinated, resulting in duplications and gaps in nominations. We have reviewed the available information and rationalized it into 51 resistance genes and factors and 15 quantitative trait loci along with supporting documentation as well as genetic and molecular information. This involved multiple rounds of consultation with many of the original authors. This paper provides the foundation for naming additional genes for resistance to B. lactucae in the future as well as for deploying genes to provide more durable resistance.

GLOBIO-Aquatic, a global model of human impact on the biodiversity of inland aquatic ecosystems
Janse, J.H. ; Kuiper, J.J. ; Weijters, M.J. ; Westerbeek, E.P. ; Jeuken, M.H.J.L. ; Bakkenes, M. ; Alkemade, R. ; Mooij, W.M. ; Verhoeven, J.T.A. - \ 2015
Environmental Science & Policy 48 (2015). - ISSN 1462-9011 - p. 99 - 114.
Catchment - Cyanobacteria - Eutrophication - Hydrological disturbance - Lakes - Land use change - Rivers - Scenario analysis - Wetlands

Biodiversity in freshwater ecosystems - rivers, lakes and wetlands - is undergoing rapid global decline. Major drivers are land use change, eutrophication, hydrological disturbance, climate change, overexploitation and invasive species. We developed a global model for assessing the dominant human impacts on inland aquatic biodiversity. The system consists of a biodiversity model, named GLOBIO-Aquatic, that is embedded in the IMAGE model framework, i.e. linked to models for demography, economy, land use changes, climate change, nutrient emissions, a global hydrological model and a global map of water bodies. The biodiversity model is based on a recompilation of existing data, thereby scaling-up from local/regional case-studies to global trends. We compared species composition in impacted lakes, rivers and wetlands to that in comparable undisturbed systems. We focussed on broad categories of human-induced pressures that are relevant at the global scale. The drivers currently included are catchment land use changes and nutrient loading affecting water quality, and hydrological disturbance and climate change affecting water quantity. The resulting relative mean abundance of original species is used as indicator for biodiversity intactness. For lakes, we used dominance of harmful algal blooms as an additional indicator. The results show that there is a significant negative relation between biodiversity intactness and these stressors in all types of freshwater ecosystems. In heavily used catchments, standing water bodies would lose about 80% of their biodiversity intactness and running waters about 70%, while severe hydrological disturbance would result in losses of about 80% in running waters and more than 50% in floodplain wetlands. As an illustration, an analysis using the OECD 'baseline scenario' shows a considerable decline of the biodiversity intactness in still existing water bodies in 2000, especially in temperate and subtropical regions, and a further decline especially in tropical regions in 2050. Historical loss of wetland areas is not yet included in these results. The model may inform policy makers at the global level in what regions aquatic biodiversity will be affected most and by what causes, and allows for scenario analysis to evaluate policy options.

Pathways to achieve a set of ambitious global sustainability objectives by 2050 : Explorations using the IMAGE integrated assessment model
Vuuren, D.P. van; Kok, Marcel ; Lucas, P.L. ; Prins, Anne Gerdien ; Alkemade, Rob ; Berg, Maurits van den; Bouwman, Lex ; Esch, Stefan van der; Jeuken, Michel ; Kram, Tom ; Stehfest, Elke - \ 2015
Technological Forecasting and Social Change 98 (2015). - ISSN 0040-1625 - p. 303 - 323.
Global change - Integrated assessment - Modelling - Sustainable development

In 2012, governments worldwide renewed their commitments to a more sustainable development that would eradicate poverty, halt climate change and conserve ecosystems, and initiated a process to create a long-term vision by formulating Sustainable Development Goals (SDGs). Although progress in achieving a more sustainable development has been made in some areas, overall, actions have not been able to bend the trend in critical areas (including those related to the so-called food-water-energy nexus). Here, we analyze how different combinations of technological measures and behavioral changes could contribute to achieving a set of sustainability objectives, taking into account the interlinkages between them. The objectives include eradicating hunger, providing universal access to modern energy, preventing dangerous climate change, conserving biodiversity and controlling air pollution. The analysis identifies different pathways that achieve these objectives simultaneously, but they all require substantial transformations in the energy and food systems, that go far beyond historic progress and currently formulated policies. The analysis also shows synergies and trade-offs between achieving the different objectives, concluding that achieving them requires a comprehensive approach. The scenario analysis does not point at a fundamental trade-off between the objectives related to poverty eradication and those related to environmental sustainability. The different pathways of achieving the set of long-term objectives and their implications for short-term action can contribute to building a comprehensive strategy to meet the SDGs by proposing near-term actions.

Zelfvoorzienend in zoetwater: zoek de mogelijkheden : kleinschalige oplossingen voor een robuustere regionale zoetwatervoorziening
Jeuken, A. ; Tolk, L. ; Stuyt, L.C.P.M. ; Delsman, J. ; Louw, P. de; Baaren, E. van; Paalman, M. - \ 2015
Amersfoort : Stowa (Rapport / STOWA 2015-30) - ISBN 9789057736940 - 73 p.
watervoorziening - watertekort - zoet water - waterbeheer - watergebruik - zelfvoorziening - klimaatverandering - water supply - water deficit - fresh water - water management - water use - self sufficiency - climatic change
In deze STOWA publicatie ‘Zoek het zelf uit’: Kleinschalige oplossingen voor een robuustere regionale zoetwatervoorziening wordt een overzicht gegeven van de maatregelen die waterbeheerders en watergebruikers in de regio kunnen treffen om de zelfvoorzienendheid op het gebied van zoetwater te vergroten. Dit sluit aan bij de ambities die in het Deltaprogramma zijn geformuleerd om de watertekorten die in de toekomst worden verwacht naast de maatregelen in het hoofdwatersysteem met lokale maatregelen in de regio te ondervangen. Er is een groot aantal van dit soort maatregelen beschikbaar om de neerslag die in een gebied valt beter te benutten, waarmee de zelfvoorzienendheid kan worden vergroot. Een flink aantal pilot studies loopt nog of zijn in het recente verleden afgerond.
Genetic investigation of the nonhost resistance of wild lettuce, Lactuca saligna, to lettuce downy mildew, Bremia lactucae
Boer, E. den - \ 2014
University. Promotor(en): Richard Visser, co-promotor(en): Marieke Jeuken; Rients Niks. - Wageningen : Wageningen University - ISBN 9789462572072 - 186
lactuca saligna - schimmelziekten - bremia lactucae - ziekteresistentie - terugkruisen - inteeltlijnen - genetische kartering - lactuca sativa - fungal diseases - disease resistance - backcrossing - inbred lines - genetic mapping


Downy mildew (Bremia lactucae) in lettuce (Lactuca sativa) is a devastating foliar disease causing high losses in lettuce cultivation. The wild lettuce and nonhost species, Lactuca saligna, is absolute resistant to downy mildew and cross-fertile with L. sativa, albeit with a low success rate and occasional reduced fertility and/or vitality in later inbred generations. This exceptional availability of hybrid plant offsprings creates a unique opportunity to study nonhost resistance by a genetic approach.

The L. saligna nonhost resistance genes might be more durable than the classical monogenic race-specific R genes that are mainly used in lettuce breeding. The identification of genes conferring nonhost resistance is a crucial step in its understanding and usage in breeding.

In this thesis the quantitative resistances of three backcross introgression lines (BILs), carrying an individual 30 to 50 cM long introgression segment from L. saligna in a L. sativa background, were fine mapped. Disease evaluation of sub-BILs with smaller introgression segments revealed that the resistance of all three BILs was explained by 17 sub-QTLs with a smaller and plant stage dependent effect, some segments reducing, others even promoting downy mildew infection.

Further the potential of stacking quantitative resistances of eight BILs per combinations of two was tested under field conditions. Only three out of ten double-combinations resulted in an increased resistance level compared to their parental individual lines, from which one had additive and two had epistatic interactions between the introgressions.

As the studies on individual QTL effects of BILs did not reveal potential genetic interactions that could explain the complete resistance of L. saligna, a novel approach was set out to search for indications of epistatic interactions. ‘Selective genotyping’ was applied on the phenotypic disease extremes of large F2 offsprings, in which multi-locus interactions between L. saligna alleles are still prevalent. In a kind of bulked segregant analysis approach four major resistance regions were identified. Preliminary results showed epistatic interactions between the regions on Chromosome 6 and 1 and between Chromosome 6 and 7.

During the development of sub-BILs, a digenic hybrid incompatibility was observed: plants carrying a L. saligna segment on Chromosome 6 always required a L. saligna segment on Chromosome 4. Segregation analysis suggested a prezygotic reproductive barrier by non-transmission of one specific hybrid gametophyte (male and female).

In cooperation with the research group of Guido van den Ackerveken of University Utrecht a lettuce germplasm screening was conducted for candidate downy mildew effector proteins, which interact with resistance genes in lettuce and trigger a defence response. One of two responsive effector proteins, ‘BLG01’, triggered a hypersensitive cell death response in most tested L. saligna accessions and its response was mapped on Chromosome 9.

Despite the complex interactions between resistance QTLs, this thesis research has delivered many insights that are important steps forward towards understanding the incompatible interaction between B. lactucae and L. saligna and its future application in resistance breeding.

Serving many at once: How a database approach can create unity in dynamical ecosystem modelling
Mooij, W.M. ; Brederveld, R.J. ; Klein, J.J.M. de; DeAngelis, D.L. ; Downing, A.S. ; Faber, M. ; Gerla, D.J. ; Hipsey, M.R. ; Hoen, J. 't; Janse, J.H. ; Janssen, A.B.G. ; Jeuken, M. ; Kooi, B.W. ; Lischke, B. ; Petzoldt, T. ; Postma, L. ; Schep, S.A. ; Scholten, H. ; Teurlincx, S. ; Thiange, C. ; Trolle, D. ; Dam, A.A. van; Gerven, L.P.A. van; Nes, E.H. van; Kuiper, J.J. - \ 2014
Environmental Modelling & Software 61 (2014). - ISSN 1364-8152 - p. 266 - 273.
shallow lakes - simulation - eutrophication - management - package - pclake
Simulation modelling in ecology is a field that is becoming increasingly compartmentalized. Here we propose a Database Approach To Modelling (DATM) to create unity in dynamical ecosystem modelling with differential equations. In this approach the storage of ecological knowledge is independent of the language and platform in which the model will be run. To create an instance of the model, the information in the database is translated and augmented with the language and platform specifics. This process is automated so that a new instance can be created each time the database is updated. We describe the approach using the simple Lotka-Volterra model and the complex ecosystem model for shallow lakes PCLake, which we automatically implement in the frameworks OSIRIS, GRIND for MATLAB, ACSL, R, DUFLOW and DELWAQ. A clear advantage of working in a database is the overview it provides. The simplicity of the approach only adds to its elegance. © 2014 The Authors.
Effects of stacked quantitative resistances to downy mildew in lettuce do not simply add up
Boer, E. den; Pelgrom, K.T.B. ; Zhang, N. ; Visser, R.G.F. ; Niks, R.E. ; Jeuken, M.J.W. - \ 2014
Theoretical and Applied Genetics 127 (2014)8. - ISSN 0040-5752 - p. 1805 - 1816.
backcross inbred lines - lactuca-saligna - bremia-lactucae - epistatic interactions - trait loci - 3 qtls - nonhost resistance - isogenic lines - heading date - wild lettuce
Key message In a stacking study of eight resistance QTLs in lettuce against downy mildew, only three out of ten double combinations showed an increased resistance effect under field conditions. Abstract Complete race nonspecific resistance to lettuce downy mildew, as observed for the nonhost wild lettuce species Lactuca saligna, is desired in lettuce cultivation. Genetic dissection of L. saligna’s complete resistance has revealed several quantitative loci (QTL) for resistance with field infection reductions of 30–50 %. To test the effect of stacking these QTL, we analyzed interactions between homozygous L. saligna CGN05271 chromosome segments introgressed into the genetic background of L. sativa cv. Olof. Eight different backcross inbred lines (BILs) with single introgressions of 30–70 cM and selected predominately for quantitative resistance in field situations were intercrossed. Ten developed homozygous lines with stacked introgression segments (double combinations) were evaluated for resistance in the field. Seven double combinations showed a similar infection as the individual most resistant parental BIL, revealing epistatic interactions with ‘less-than-additive’ effects. Three double combinations showed an increased resistance level compared to their parental BILs and their interactions were additive, ‘less-than-additive’ epistatic and ‘more-than-additive’ epistatic, respectively. The additive interaction reduced field infection by 73 %. The double combination with a ‘morethan-additive’ epistatic effect, derived from a combination between a susceptible and a resistant BIL with 0 and 30 % infection reduction, respectively, showed an average field infection reduction of 52 %. For the latter line, an attempt to genetically dissect its underlying epistatic loci by substitution mapping did not result in smaller mapping intervals as none of the 22 substitution lines reached a similar high resistance level. Implications for breeding and the inheritance of L. saligna’s complete resistance are discussed.
De strijd om het zaad
Jeuken, Marieke - \ 2013

Interview TV programma VPRO tegenlicht

Assessing the impacts of livestock production on biodiversity in rangeland ecosystems
Alkemade, R. ; Reid, R.S. ; Berg, M. van den; Leeuw, J. de; Jeuken, M. - \ 2013
Proceedings of the National Academy of Sciences of the United States of America 110 (2013)52. - ISSN 0027-8424 - p. 20900 - 20905.
land-use changes - south-africa - diversity - conservation - assemblages - grassland - management - scenarios - responses - savanna
Biodiversity in rangelands is decreasing, due to intense utilization for livestock production and conversion of rangeland into cropland; yet the outlook of rangeland biodiversity has not been considered in view of future global demand for food. Here we assess the impact of future livestock production on the global rangelands area and their biodiversity. First we formalized existing knowledge about livestock grazing impacts on biodiversity, expressed in mean species abundance (MSA) of the original rangeland native species assemblages, through metaanalysis of peer-reviewed literature. MSA values, ranging from 1 in natural rangelands to 0.3 in man-made grasslands, were entered in the IMAGE-GLOBIO model. This model was used to assess the impact of change in food demand and livestock production on future rangeland biodiversity. The model revealed remarkable regional variation in impact on rangeland area and MSA between two agricultural production scenarios. The area of used rangelands slightly increases globally between 2000 and 2050 in the baseline scenario and reduces under a scenario of enhanced uptake of resource-efficient production technologies increasing production [high levels of agricultural knowledge, science, and technology (high-AKST)], particularly in Africa. Both scenarios suggest a global decrease in MSA for rangelands until 2050. The contribution of livestock grazing to MSA loss is, however, expected to diminish after 2030, in particular in Africa under the high-AKST scenario. Policies fostering agricultural intensification can reduce the overall pressure on rangeland biodiversity, but additional measures, addressing factors such as climate change and infrastructural development, are necessary to totally halt biodiversity loss.
Tipping from the Holocene to the Anthropocene: How threatened are major world deltas?
Renaud, F.G. ; Syvitski, J.P.M. ; Werners, S.E. ; Kremer, H. ; Kuenzer, C. ; Ramesh, R. ; Jeuken, A. - \ 2013
Current Opinion in Environmental Sustainability 5 (2013)6. - ISSN 1877-3435 - p. 644 - 654.
social-ecological systems - sea-level rise - climate-change - mississippi delta - northern india - river - thresholds - discharge - sediment - impact
Coastal deltas are landforms that typically offer a wide variety of benefits to society including highly fertile soils for agricultural development, freshwater resources, and rich biodiversity. For these reasons, many deltas are densely populated, are important economic hubs, and have been transformed by human interventions such as agricultural intensification, modification of water and sediment fluxes, as well as urbanization and industrialization. Additionally, deltas are increasingly affected by the consequences of climate change including sea level rise, and by other natural hazards such as cyclones and storm surges. Five examples of major deltas (Rhine-Meuse, Ganges, Indus, Mekong, and Danube) illustrate the force of human interventions in shaping and transforming deltas and in inducing shifts between four different social-ecological system (SES) states: Holocene, modified Holocene, Anthropocene and ‘collapsed’. The three Asian deltas are rapidly changing but whereas SES in the Ganges and Indus deltas are in danger of tipping into a ‘collapsed’ state, SES in the Mekong delta, which is at the crossroads of various development pathways, could increase in resilience in the future. The Rhine-Meuse and Danube delta examples show that highly managed states may allow, under specific conditions, for interventions leading to increasingly resilient systems. However, little is known about the long-term effects of rapid human interventions in deltas. It is therefore critical to increase the knowledge-base related to SES dynamics and to better characterize social tipping points or turning points in order to avoid unacceptable changes.
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