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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Test sorghumrassen op vier proeflocaties
Agtmaal, Maaike van; Deru, Joachim ; Eekeren, Nick van; Pannecoucque, J. - \ 2019
V-focus (2019)2. - ISSN 1574-1575 - p. 20 - 22.
Achtergronden bij informatie in de BOOT-lijst factsheets
Verloop, Koos ; Agtmaal, Maaike van; Busink, Wim ; Eekeren, Nick van; Groenendijk, Piet ; Jansen, Stefan ; Noij, Gert-Jan ; Zanen, Marleen - \ 2018
Wageningen : Stichting Wageningen Research, Wageningen Plant Research, Business unit Agrosysteemkunde (Rapport WPR 842) - 133
Vanuit het Bestuurlijk Overleg Open Teelt en Veehouderij (BOOT) is de zogenaamde BOOT-lijst opgesteld met maatregelen die emissie naar water vanuit landbouwbedrijven verlagen. De praktijkrijpe maatregelen worden via het Deltaplan Agrarisch Waterbeheer (DAW) verder uitgerold. Factsheets over 24 van de maatregelen geven inzicht in het productievoordeel, het milieuvoordeel en de kosten en in de praktische inpasbaarheid. Dit rapport voorziet in achtergrondinformatie en onderbouwing van de factsheets en geeft aan in hoeverre er consensus is over de gepresenteerde inzichten. Bij veel maatregelen is er behoefte aan versterking van de empirische onderbouwing. Adviezen over te nemen maatregelen kunnen aan overtuigingskracht winnen als resultaten van veldonderzoek beschikbaar zijn. Een aantal maatregelen heeft betrekking op verandering van bodemaspecten (zoals het bodem organische stofgehalte) zonder dat de relatie van deze doelen met waterkwaliteit voldoende duidelijk is uitgewerkt. De effectiviteit van deze maatregelen op uiteindelijke waterkwaliteitsdoelen moet scherper in het vizier komen.
Volatile-mediated suppression of plant pathogens is related to soil properties and microbial community composition
Agtmaal, Maaike van; Straathof, Angela L. ; Termorshuizen, Aad ; Lievens, Bart ; Hoffland, Ellis ; Boer, Wietse de - \ 2018
Soil Biology and Biochemistry 117 (2018). - ISSN 0038-0717 - p. 164 - 174.
Fusarium oxysporum - Phytopathology - Pythium intermedium - Rhizoctonia solani - Soil microbial ecology - Soil-borne plant pathogens - Volatile organic compounds

There is increasing evidence that the soil microbial community produces a suite of volatile organic compounds that suppress plant pathogens. However, it remains unknown which soil properties and management practices influence volatile-mediated pathogen suppression. The aim of this study was to relate soil properties to growth suppression of three plant pathogens by soil volatiles. We measured the effect of volatiles emitted from a broad range of agricultural soils on the in vitro growth of the plant pathogenic fungi Rhizoctonia solani and Fusarium oxysporum, and the oomycete Pythium intermedium. Growth suppression of pathogens by soil volatiles could be linked to various soil properties, and some aspects of microbial community composition and field history, using multiple linear regression. Volatile-mediated suppression of mycelial development occurred for each pathogen type, but the magnitude of inhibition differed among soils as well as pathogens. On average R. solani and P. ultimum appeared more sensitive to volatile suppression than F. oxysporum. Suppression of R. solani by volatiles was positively correlated with organic matter content, microbial biomass and proportion of litter saprotrophs in the microbial community, but negatively correlated with pH, microbial diversity (Shannon), and the proportion of Acidobacteria in the community. R. solani, F. oxysporum, and P. intermedium suppression by volatiles was affected by various management practices occurring in the soil's field history, such as reduced tillage, the presence of certain crops in the crop rotation, and the application of solid manure. P. intermedium suppression was also negatively correlated with soil sulphur content. This study identifies pathogen-specific drivers of growth-suppressive volatiles, a critical step in integrating soil volatiles into prediction and management of soil-borne plant diseases.

Exploring the reservoir of potential fungal plant pathogens in agricultural soil
Agtmaal, M. van; Straathof, Angela ; Termorshuizen, Aad ; Teurlincx, Sven ; Hundscheid, Maria ; Ruyters, Stefan ; Busschaert, Pieter ; Lievens, Bart ; Boer, Wietse de - \ 2017
Applied Soil Ecology 121 (2017). - ISSN 0929-1393 - p. 152 - 160.
Community dynamics - Fungi - Oomycetes - Soil-borne plant pathogens - Surviving propagules

Soil-borne pathogens cause great crop losses in agriculture. Because of their resilience in the soil, these pathogens persist in a population reservoir, causing future outbreaks of crop diseases. Management focus is usually on the most common pathogens occurring, but it is likely that a mixed population of pathogens together affect crops. Next generation sequencing of DNA from environmental samples can provide information on the presence of potential pathogens. The aim of this study was to obtain insight into the factors that drive the composition of potential plant pathogen populations in agricultural soils. To this end, the alpha and beta diversity of fungal OTUs that were assigned as potential plant pathogens for 42 agricultural soils were assessed. The presented study is the first inventory of the pool of pathogens and its correlating factors. The results of this inventory indicate that the composition of pathogens in soil is driven by pH, soil type, crop history, litter saprotrophic fungi and spatial patterns. The major driving factors differed between potential root- and shoot-infecting fungi, suggesting interactions among environmental factors and pathogen traits like reproduction, survival and dispersal. This information is important to understand risks for disease outbreaks and to recommend management strategies to prevent such outbreaks.

Data from: Soil pathogen-aphid interactions under differences in soil organic matter and mineral fertilizer
Gils, S.H. van; Tamburini, Giovanni ; Marini, Lorenzo ; Biere, Arjen ; Agtmaal, M. van; Tyc, Olaf ; Kos, M. ; Kleijn, D. ; Putten, W.H. van der - \ 2017
Wageningen University & Research
Rhizoctonia solani - Sitobion avenae - Triticum aestivum
There is increasing evidence showing that microbes can influence plant-insect interactions. In addition, various studies have shown that aboveground pathogens can alter the interactions between plants and insects. However, little is known about the role of soil-borne pathogens in plant-insect interactions. It is also not known how environmental conditions, that steer the performance of soil-borne pathogens, might influence these microbe-plant-insect interactions. Here, we studied effects of the soil-borne pathogen Rhizoctonia solani on aphids (Sitobion avenae) using wheat (Triticum aestivum) as a host. In a greenhouse experiment, we tested how different levels of soil organic matter (SOM) and fertilizer addition influence the interactions between plants and aphids. To examine the influence of the existing soil microbiome on the pathogen effects, we used both unsterilized field soil and sterilized field soil. In unsterilized soil with low SOM content, R. solani addition had a negative effect on aphid biomass, whereas it enhanced aphid biomass in soil with high SOM content. In sterilized soil, however, aphid biomass was enhanced by R. solani addition and by high SOM content. Plant biomass was enhanced by fertilizer addition, but only when SOM content was low, or in the absence of R. solani. We conclude that belowground pathogens influence aphid performance and that the effect of soil pathogens on aphids can be more positive in the absence of a soil microbiome. This implies that experiments studying the effect of pathogens under sterile conditions might not represent realistic interactions. Moreover, pathogen-plant-aphid interactions can be more positive for aphids under high SOM conditions. We recommend that soil conditions should be taken into account in the study of microbe-plant-insect interactions.
Soil pathogen-aphid interactions under differences in soil organic matter and mineral fertilizer
Gils, Stijn van; Tamburini, Giovanni ; Marini, Lorenzo ; Biere, Arjen ; Agtmaal, Maaike van; Tyc, Olaf ; Kos, Martine ; Kleijn, David ; Putten, Wim H. van der - \ 2017
PLoS ONE 12 (2017)8. - ISSN 1932-6203 - 14 p.

There is increasing evidence showing that microbes can influence plant-insect interactions. In addition, various studies have shown that aboveground pathogens can alter the interactions between plants and insects. However, little is known about the role of soil-borne pathogens in plant-insect interactions. It is also not known how environmental conditions, that steer the performance of soil-borne pathogens, might influence these microbe-plant-insect interactions. Here, we studied effects of the soil-borne pathogen Rhizoctonia solani on aphids (Sitobion avenae) using wheat (Triticum aestivum) as a host. In a greenhouse experiment, we tested how different levels of soil organic matter (SOM) and fertilizer addition influence the interactions between plants and aphids. To examine the influence of the existing soil microbiome on the pathogen effects, we used both unsterilized field soil and sterilized field soil. In unsterilized soil with low SOM content, R. solani addition had a negative effect on aphid biomass, whereas it enhanced aphid biomass in soil with high SOM content. In sterilized soil, however, aphid biomass was enhanced by R. solani addition and by high SOM content. Plant biomass was enhanced by fertilizer addition, but only when SOM content was low, or in the absence of R. solani. We conclude that belowground pathogens influence aphid performance and that the effect of soil pathogens on aphids can be more positive in the absence of a soil microbiome. This implies that experiments studying the effect of pathogens under sterile conditions might not represent realistic interactions. Moreover, pathogen-plant-aphid interactions can be more positive for aphids under high SOM conditions. We recommend that soil conditions should be taken into account in the study of microbe-plant-insect interactions.

Non-random species loss in bacterial communities reduces antifungal volatile production
Hol, G. ; Garbeva, P. ; Hordijk, C. ; Hundscheid, M.P.J. ; Klein Gunnewiek, P.J.A. ; Agtmaal, M. van; Boer, W. de - \ 2015
Ecology 96 (2015)8. - ISSN 0012-9658 - p. 2042 - 2048.
The contribution of low-abundance microbial species to soil ecosystems is easily overlooked because there is considerable overlap between metabolic abilities (functional redundancy) of dominant and subordinate microbial species. Here we studied how loss of less abundant soil bacteria affected the production of antifungal volatiles, an important factor in the natural control of soil-borne pathogenic fungi. We provide novel empirical evidence that the loss of soil bacterial species leads to a decline in the production of volatiles that suppress root pathogens. By using dilution-to-extinction for seven different soils we created bacterial communities with a decreasing number of species and grew them under carbon-limited conditions. Communities with high bacterial species richness produced volatiles that strongly reduced the hyphal growth of the pathogen Fusarium oxysporum. For most soil origins loss of bacterial species resulted in loss of antifungal volatile production. Analysis of the volatiles revealed that several known antifungal compounds were only produced in the more diverse bacterial communities. Our results suggest that less abundant bacterial species play an important role in antifungal volatile production by soil bacterial communities and, consequently, in the natural suppression of soil-borne pathogens.
Legacy effects of anaerobic soil disinfestation on soil bacterial community composition and production of pathogen-suppressing volatiles
Os, G.J. van; Agtmaal, M. van; Hol, G. ; Hundscheid, M.P.J. ; Runia, W.T. ; Hordijk, C. ; Boer, W. de - \ 2015
Frontiers in Microbiology 6 (2015). - ISSN 1664-302X
pythium root-rot - soilborne plant-diseases - microbial-populations - organic amendments - biological-control - bulbous iris - fungistasis - growth - biocontrol - diversity
There is increasing evidence that microbial volatiles (VOCs) play an important role in natural suppression of soil-borne diseases, but little is known on the factors that influence production of suppressing VOCs. In the current study we examined whether a stress-induced change in soil microbial community composition would affect the production by soils of VOCs suppressing the plant-pathogenic oomycete Pythium. Using pyrosequencing of 16S ribosomal gene fragments we compared the composition of bacterial communities in sandy soils that had been exposed to anaerobic disinfestation (AD), a treatment used to kill harmful soil organisms, with the composition in untreated soils. Three months after the AD treatment had been finished, there was still a clear legacy effect of the former anaerobic stress on bacterial community composition with a strong increase in relative abundance of the phylum Bacteroidetes and a significant decrease of the phyla Acidobacteria, Planctomycetes, Nitrospirae, Chloroflexi, and Chlorobi. This change in bacterial community composition coincided with loss of production of Pythium suppressing soil volatiles (VOCs) and of suppression of Pythium impacts on Hyacinth root development. One year later, the composition of the bacterial community in the AD soils was reflecting that of the untreated soils. In addition, both production of Pythium-suppressing VOCs and suppression of Pythium in Hyacinth bioassays had returned to the levels of the untreated soil. GC/MS analysis identified several VOCs, among which compounds known to be antifungal, that were produced in the untreated soils but not in the AD soils. These compounds were again produced 15 months after the AD treatment. Our data indicate that soils exposed to a drastic stress can temporarily lose pathogen suppressive characteristics and that both loss and return of these suppressive characteristics and that both loss and return of these suppressive characteristics coincides with shifts in the soil bacterial community composition. Our data are supporting the suggested importance of microbial VOCs in the natural buffer of soils against diseases caused by soil-borne pathogens.
Suppression of soil-borne plant pathogens
Agtmaal, M. van - \ 2015
Wageningen University. Promotor(en): Wietse de Boer; J.A. van Veen. - Wageningen : Wageningen University - ISBN 9789462572911 - 151
plantenziekteverwekkers - bodempathogenen - bodembacteriën - desinfecteren - landbouwgronden - modellen - rizosfeer - ziektewerende gronden - plant pathogens - soilborne pathogens - soil bacteria - disinfestation - agricultural soils - models - rhizosphere - suppressive soils

Soil borne plant pathogens considerably reduce crop yields worldwide and are difficult to control due to their ”masked” occurrence in the heterogeneous soil environment. This hampers the efficacy of chemical - and microbiological control agents. Outbreaks of crop diseases are not only dependent on the presence of pathogen propagules in the soil, but are also influenced by soil-related properties like physico-chemical characteristics, microbial activity and community composition. Strong competition for limited available carbon substrates restricts or prevents germination and pre-infective growth of pathogens. This competition can occur directly by rapid exploitation of substrates, so called resource competition, or indirectly via inhibitory secondary metabolites, called interference competition

The overall effect of all competition based mechanisms and the abiotic environment on disease development is known as “general disease suppression” and is the sum of all factors that reduce disease. The aim of this thesis was to study different aspects of general disease suppression, in order to get more insight into the interplay between microbial communities, pathogen dynamics, and substrate availability in different agricultural soils.

The first objective was to study the role of microbial volatile organic compounds in natural disease suppression in agricultural soils. In chapter 2 a series of simultaneous experiments were performed on a agricultural soil that received different management practises. We showed a strong correlation between root infection and -biomass production in a bioassay and the suppressive effects of microbial volatiles on the in vitro growth of the pathogen Pythium intermedium. No or weak volatile suppression coincided with significant lower root biomass and a higher disease index, whereas a strong volatile suppression related to high biomass and a low disease index. Furthermore, the composition of the original soil bacterial community showed a drastic shift due to the legacy effects of management practices, coinciding with the loss of volatile suppression. By comparing the emission profiles and the bacterial community composition of the differently managed soils, candidate inhibitory compounds and volatile producing bacterial groups could be identified. Altogether these results indicate that volatile organic compounds can have an important role in general disease suppression.

To follow up on volatile suppression chapter 3 investigates the influence of soil-related (abiotic and biotic) variables on volatile mediated in vitro growth inhibition of different plant pathogens via an extensive soil survey including 50 Dutch arable agricultural fields. The volatile mediated suppression of three phylogenetic different soil borne pathogens (Rhizoctonia solani, Fusarium oxysporum and Pythium intermedium) was linked to a wide range of soil-related variables with univariate and multivariate regression models. The overall suppression of different pathogens was linked to microbial activity and organic substrates. However, different pathogens showed different sensitivity to volatile suppression. Furthermore, the soil-related factors corresponding to volatile mediated suppression were pathogen specific. In total, the results described in this chapter show that part of volatile suppression for a particular pathogen is based on general microbial activity, but our data shows as well that the individual response is pathogen specific.

Chapter 4 explores the reservoir of potential plant pathogens harboring agricultural soils before the start of the growth season, together with the environmental drivers of this pool of pathogens. By investigating the pathogenic seedbank in relation to its environment we assessed which soil-related variables could explain differences among site pathogen community composition. Pathogens differing in phylogeny or mode of infection were related to different soil variables. For example the among-site differences in the presence of oomycetes could not be related to their environmental context. On the other hand the variation in root and shoot fungal pathogen community composition was linked to soil physico-chemical properties and non-pathogen microbial community composition, with potentially a significant role of litter saprophytes therein.

As the presence of pathogen propagules in soil is not necessarily related to disease incidence, chapter 5 investigates the dynamics of root pathogens in the presence of a root in a model rhizosphere. We developed a qPCR based assay to test the growth response of a pathogen (Pythium intermedium) to the presence of root exudates over time. This exposure to root exudates showed soil specific pathogen dynamics. This finding may indicate that in situ (microbial) processes can successfully prevent pathogen development in some of the soils but not in others. Thus this method has the potential to provide an alternative way to assess the susceptibility of a soil to certain soil-borne diseases.

The results of this thesis gave new insights into different aspects of disease suppression in agricultural soils which could serve as a fundament to develop environmentally-friendly control methods based on natural occurring ecological processes. Ideas for the implementation of this study and future research are discussed in chapter 6.

Remote beneficials in soil; potential role of bacterial volatiles in suppression of soil-borne fungal pathogens
Agtmaal, M. van; Hundscheid, M.P.J. ; Straathof, A.L. ; Boer, W. de - \ 2013
Gewasbescherming 44 (2013)5. - ISSN 0166-6495 - p. 136 - 136.
A nematode venom allergen protein interacts with a cathepsin-like cysteine protease in the host and is required for plant parasitism
Lozano, J. ; Wilbers, R.H.P. ; Gawronski, P. ; Agtmaal, M. van; Overmars, H.A. ; Klooster, J. van t; Wit, P.J.G.M. de; Goverse, A. ; Bakker, J. ; Smant, G. - \ 2009
In: ISMPMI International Congress abstracts, Quebec City, Canada, 19-23 July 2009. - Quebec : MPMI - p. 350 - 350.
A nematode venom allergen protein interacts with a cathepsin-like cysteine protease in the host and is required for the plant parasitism
Lozano, J. ; Wilbers, R.H.P. ; Gawronski, J.H. ; Agtmaal, M. van; Qin Ling, ; Overmars, H.A. ; Klooster, J.W. van t; Wit, P.J.G.M. de; Goverse, A. ; Bakker, J. ; Smant, G. - \ 2009
In: BioExploit Science Meeting. Exploitation of natural plant biodiversity for the pesticide-free production of food, 31 March-4 April 2009. - - p. 21 - 21.
Waxy variegation in transgenic potato.
Pereira, A. ; Aarts, M. ; Agtmaal, S. van; Stiekema, W.J. ; Jacobsen, E. - \ 1991
Maydica 36 (1991). - ISSN 0025-6153 - p. 323 - 326.
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