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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Potatoes, pathogens and pests : effects of genetic modifi cation for plant resistance on non-target arthropods
Lazebnik, Jenny - \ 2017
University. Promotor(en): Joop van Loon; Marcel Dicke. - Wageningen : Wageningen University - ISBN 9789463431620 - 151
solanum tuberosum - potatoes - oomycetes - phytophthora infestans - genetic engineering - transgenic plants - disease resistance - risk assessment - nontarget organisms - arthropods - insect pests - herbivores - trophic levels - ecological risk assessment - greenhouse experiments - field experimentation - aardappelen - oömyceten - genetische modificatie - transgene planten - ziekteresistentie - risicoschatting - niet-doelorganismen - geleedpotigen - insectenplagen - herbivoren - trofische graden - ecologische risicoschatting - kasproeven - experimenteel veldonderzoek

Currently, fungicides are necessary to protect potato crops against late blight, Phytophthora infestans, one of the world’s most damaging crop pathogens. The introgression of plant resistance genes from wild potato species targeted specifically to the late blight pathogen into susceptible potato varieties may alleviate the environmental impact of chemical control. Genetically modified plants are subject to an environmental risk assessment, and this includes testing for risks to the non-target arthropod community associated with the crop. The thesis begins with a review about the main plant defense responses and their role in influencing sequential interactions between herbivores and plant pathogens. The experimental chapters each focus on different aspects of the interaction between potato plants (both resistant and susceptible), the target pathogen (P. infestans) and several non-target insects. With each chapter, the scope widens: from the molecular gene expression in potato leaves in response to sequential attacks, to field scale biodiversity analyses. At the molecular level, one of the main findings was that the genomic position of the Rpi-vnt1 insertion conferring resistance to P. infestans influenced potato gene expression measured in leaves, when interacting with the non-target insect pests Myzus persicae (Green peach aphid) and Leptinotarsa decemlineata (Colorado potato beetle). Insect performance differed between the resistant GM and susceptible non-GM comparator. In the following chapter, the differences in insect performance were tested across a range of conventionally bred cultivars varying in resistance to P. infestans. Differences in M. persicae performance between several cultivars greatly outweighed the differences previously detected between the GM and non-GM comparator. These results are crucial in shaping the way risk is assessed in the context of GM crops, and these results are supported in our experiments assessing effects on biodiversity with pitfall traps in the field. The third trophic level was also addressed by comparing the performance of the parasitoid Aphidius colemani reared on GM and non-GM fed aphids, both with an without exposure to P. infestans. Differences in parasitoid performance were only found on the susceptible cultivar when inoculated with P. infestans. In the last experimental chapter the risk assessment is taken to the field comparing pitfall trap catches over two years and in two countries. Different methods for statistical analysis of biodiversity data were compared to arrive at recommendations for such analysis in the framework of environmental risk assessments. Drawing on these lessons, the discussion ends with ideas for the development of protocols for environmental risk assessments in the light of expected scientific progress in agricultural biotechnology.

Susceptibility genes : an additional source for improved resistance
Sun, Kaile - \ 2017
University. Promotor(en): Richard Visser, co-promotor(en): Evert Jacobsen; Yuling Bai. - Wageningen : Wageningen University - ISBN 9789463431415 - 174
solanum tuberosum - potatoes - solanum lycopersicum - tomatoes - genes - susceptibility - plant pathogenic fungi - phytophthora infestans - disease resistance - plant breeding - aardappelen - tomaten - genen - vatbaarheid - plantenziekteverwekkende schimmels - ziekteresistentie - plantenveredeling

Potato is affected by several diseases. Although, resistance can be obtained by introgression of major resistance genes from wild species, this has rarely been durable. Hence, other sources of resistance are highly needed. New research with a focus on loss of function mutations has led to the identification of disease susceptibility (S) genes in plants. The research in this thesis was aimed at the identification and characterization of potato S genes involved in the interaction with Phytophthora infestans and Botrytis cinerea. We selected 11 Arabidopsis thaliana S genes and silenced their potato orthologs by RNAi in the potato cultivar Desiree. The silencing of six genes resulted in resistance to P. infestans. Moreover, silencing of StDND1 reduced the infection of B. cinerea. Microscopic analysis showed that spore attachment and/or germination of P. infestans and B. cinerea was hampered on the leaf surface of StDND1-silenced potato plants. On StDMR1- and StDMR6-silenced potato plants, hyphal growth of P. infestans was arrested by the hypersensitive response-like cell death. Our results demonstrate that impairment of plant S genes may open a new way for breeding potatoes with resistance to pathogens like P. infestans and B. cinerea.

Fungicide evaluation to rate efficacy to control leaf late blight for the EuroBlight table Results 2006-2015
Evenhuis, A. ; Bain, R. ; Hausladen, H. ; Nielsen, B.J. ; Berg, W. van den; Schepers, H.T.A.M. - \ 2016
Lelystad : Applied Plant Research - 46 p.
solanum tuberosum - potatoes - plant pathogenic fungi - oomycetes - phytophthora infestans - fungicides - protocols - field experimentation - europe - aardappelen - plantenziekteverwekkende schimmels - oömyceten - fungiciden - protocollen - experimenteel veldonderzoek - europa
Hevige phytophthora-uitbraak 2016 benadrukt noodzaak resistente rassen
Lammerts Van Bueren, E. ; Hutten, R.C.B. ; Engelen, C.J.M. - \ 2016
Aardappelwereld 2016 (2016)9. - ISSN 0169-653X - p. 32 - 33.
phytophthora infestans - aardappelen - biologische landbouw - ziekteresistentie - resistentie van variëteiten - rassen (planten) - plantenveredeling - potatoes - organic farming - disease resistance - varietal resistance - varieties - plant breeding
De biologische aardappelteelt heeft het in 2016 weer zwaar te verduren gehad met de hevige uitbraak van Phytophtora infestans. Door aanhoudende regenval in juni en juli waren veel telers genoodzaakt om hun percelen met aangetaste aardappelen al vroeg in het seizoen te branden. Gecombineerd met de late pootdatum hebben velen een (te) lage opbrengst van hun vatbare rassen dit jaar. "DIt bevestigt nog maar weer eens de noodzaak van resistente rassen", zo stellen Edith Lammerts van Bueren, Ronald Hutten en Christel Engelen, van het project Bioimpuls waar de deelnemers hard aan nieuwe resistente rassen werken.
Resistente aardappel hoopt op genade
Hoog, A. van 't; Haverkort, A.J. - \ 2015
WageningenWorld (2015)4. - ISSN 2210-7908 - p. 10 - 15.
akkerbouw - aardappelen - resistentieveredeling - rassen (planten) - schimmelbestrijding - phytophthora infestans - gewasbescherming - arable farming - potatoes - resistance breeding - varieties - fungus control - plant protection
Met Wageningse gentechnologie zijn aardappels te ontwikkelen die amper bestrijdingsmiddelen nodig hebben tegen de aardappelziekte Phytophthora. Toepassing zou binnen vijf jaar resistente aardappelrassen kunnen opleveren, maar genetische modificatie ligt gevoelig en iedereen wacht met smart op bericht uit Brussel. ‘We hebben nog vier maanden voordat het pootgoed begint te verrotten.’
Results of potato late blight demonstrations in Garut and Pangalengan, Indonesia, October 2014-January 2015
Schepers, H.T.A.M. ; Gunadi, N. ; Putter, H. de; Moekasan, T.K. ; Prabaningrum, L. ; Karjadi, A.K. - \ 2015
Wageningen : Wageningen UR (vegIMPACT 18) - 19 p.
vegIMPACT - arable farming - potatoes - solanum tuberosum - blight - phytophthora infestans - demonstration farms - plant protection - indonesia - akkerbouw - aardappelen - vuur (plantenziektekundig) - demonstratiebedrijven, landbouw - gewasbescherming - indonesië
Demo plots with potato varieties Atlantic and Granola were laid out in Garut and Pangalengan from October 2014 to January 2015. The objective of the demo plots described in this report are to investigate the influence of three factors on the efficacy of three factors in late blight control strategies:Test the influence of fungicide product choice on the efficacy of late blight control in the most susceptible variety Atlantic; Test the influence of spray volume on the efficacy to control late blight both in Atlantic and Granola; Test the influence of the adjuvant Agristick at normal and reduced spray volumes both in Atlantic and Granola.
Aardappel in een Biodivers teeltsysteem: resultaten 2010-2014
Wijk, C.A.P. van; Sukkel, W. ; Gruppen, R. - \ 2015
Lelystad : PPO AGV - 39
aardappelen - solanum tuberosum - teeltsystemen - biodiversiteit - biologische landbouw - bodemweerbaarheid - gewasopbrengst - rotatie - phytophthora infestans - groenbemesters - ruiterpaden - minimale grondbewerking - rijpadensysteem - potatoes - cropping systems - biodiversity - organic farming - soil suppressiveness - crop yield - rotation - green manures - bridle paths - minimum tillage - controlled traffic farming
Om de effecten van hogere biodiversiteit onder veldomstandigheden te toetsen is onderzoek gestart met een biologische teeltsysteem met veel biodiversiteitmaatregelen in een vaste rotatie van diverse gewassen. Belangrijke biodiversiteitsmaatrelen daarin zijn teelt op kleinere percelen (smalle stroken) en niet kerende grondbewerking, maar ook toepassing van rasmengsels. Dit systeem (aangeduid met systeem Biodivers) wordt vergeleken met een standaard biologisch teeltsysteem op grote percelen (aangeduid met systeem Bio-standaard). De rotatiegewassen in beide systemen zijn aardappel, grasklaver, kool, zomertarwe, peen en mixteelt van veldboon en zomertarwe. De nadere omschrijving van beide systemen staat in hoofdstuk 2. Daar worden de toegepaste biodiversiteitsmaatregelen per gewas toegelicht en de opzet van onderzoek en pilots nader beschreven.
Progress Report China Potato GAP project; Late blight control, seed quality, storage facilities and sustainability studies in Heilongjiang province and communications
Kempenaar, C. ; Kessel, G.J.T. ; Wustman, R. ; Pronk, A.A. ; Haverkort, A.J. ; Ruijter, F.J. de; Lyu, D. ; Wan, S. ; Fan, G. ; Bai, Y. ; Min, F. ; Guo, M. ; Zhang, S. ; Yang, S. ; Gao, Y. - \ 2015
Wageningen : Plant Research International (Report / Plant Research International 608) - 73
potatoes - seed potatoes - solanum tuberosum - good practices - phytophthora infestans - disease resistance - decision support systems - seed quality - land use - water use efficiency - storage - storage equipment - china - aardappelen - pootaardappelen - ziekteresistentie - beslissingsondersteunende systemen - zaadkwaliteit - landgebruik - watergebruiksrendement - opslag - voorzieningen voor de opslag
In this report we describe the mid-term results of the R&D program of the PPS Potato GAP China. The aim of the Potato GAP China PPS is to exchange information on GAP in potato production and storage, and to set up experiments and demonstration farms in China with Dutch technology and know-how. This last objective, the setup of Centres of Dutch potato Expertise in China, has not been achieved yet, but still has high priority in 2015. In this report, we describe the results of experiments, investigations and communications within the PPS in 2013 and 2014. The R&D topics are potato late blight disease monitoring and control, potato seed quality evaluation, potato storage investigation and sustainability evaluation of potato production.
Influence of adjuvants on the deposition of mancozeb
Schepers, H.T.A.M. ; Evenhuis, A. ; Topper, C.G. - \ 2014
Wageningen : Wageningen UR (vegIMPACT report 5) - 14
solanum tuberosum - aardappelen - plantenziekten - oömycota - phytophthora infestans - fungiciden - mancozeb - hulpstoffen - depositie - indonesië - potproeven - nederland - potatoes - plant diseases - oomycota - fungicides - adjuvants - deposition - indonesia - pot experimentation - netherlands
Late Blight demonstrations December 2013-February 2014
Schepers, H.T.A.M. ; Gunadi, N. ; Putter, H. de; Wustman, R. ; Moekasan, T.K. ; Laksminiwati, P. ; Karjadi, A.K. - \ 2014
Wageningen : Wageningen UR (vegIMPACT report 4) - 16
solanum tuberosum - aardappelen - solanum lycopersicum - tomaten - plantenziekten - phytophthora infestans - oömycota - gewasbescherming - fungiciden - experimenteel veldonderzoek - demonstratiebedrijven, landbouw - indonesië - potatoes - tomatoes - plant diseases - oomycota - plant protection - fungicides - field experimentation - demonstration farms - indonesia
Late blight caused by Phytophthora infestans is one of the most important diseases worldwide. Also in Indonesia control of late blight is very important in potato and tomato, especially in the rainy season. In order to learn more about the important factors that determine late blight control - such as product choice, application frequency, spray volume and use of adjuvants - two demo plots were laid out in the potato growing regions of Garut and Pangalengan. The treatments in the demo-plots consisted of different fungicide application strategies.
Phytophthora infestans RXLR effector AVR1 and its host target Sec5
Du, Y. - \ 2014
University. Promotor(en): Francine Govers, co-promotor(en): Klaas Bouwmeester. - Wageningen : Wageningen University - ISBN 9789462571310 - 188
phytophthora infestans - oömycota - plantenziekteverwekkende schimmels - virulentie - genen - plant-microbe interacties - ziekteresistentie - verdedigingsmechanismen - vatbaarheid - uitschakelen van genexpressie - oomycota - plant pathogenic fungi - virulence - genes - plant-microbe interactions - disease resistance - defence mechanisms - susceptibility - gene silencing


Late blight, caused by the oomycete Phytophthora infestans, is one of the most devastating potato diseases worldwide. To successfully colonize its host, P. infestans secretes a plethora of RXLR effectors that translocate into host cells to modulate plant defense. The RXLR effectors form the largest and most diverse effector family in oomycete plant pathogens, and include several that were demonstrated to trigger host resistance mediated by intracellular host immune receptors. Chapter 1 is a summary focussing on the molecular mechanisms underlying host–pathogen interactions. It introduces the multi-layered innate immune system of plants, as well as the strategies that pathogens exploit to circumvent and suppress host defense. Furthermore, it highlights the importance of vesicle-trafficking during plant defense.

The central subject of this thesis is AVR1, one of the race-specific avirulence (AVR) factors of P. infestans. AVR1 triggers plant resistance mediated by its corresponding potato Nucleotide-binding Leucine-rich repeat (NLR) resistance protein R1. P. infestans isolates that are avirulent on R1-containing potato cultivars always contain AVR1, while virulent isolates lack AVR1 but contain a related gene that we baptized as AVR1-like. AVR1 has all hallmarks of a typical RXLR effector; it contains a signal peptide, an RXLR domain and a C-terminal effector domain that contains two W motifs and one Y motif. In addition, it has, at the very end a stretch of 38 amino acids in length that we named the Tail (T)-region. AVR1-like, or in short A-L, shares high sequence similarity with AVR1. However, due to a premature stop codon the 38 amino acid T-region is missing.

Chapter 2 explores the conserved motifs and regions in the C-terminal effector domain of AVR1 that are required to trigger R1-mediated hypersensitive response (HR). Various truncated and chimeric constructs of AVR1 and A-L were generated and assayed for their ability to elicit R1-mediated HR. Results show that the T-region of AVR1 plays an important role in HR activation. Furthermore, we revealed that R1 recognizes two epitopes in AVR1, one located in the C-terminal region containing the conserved W and Y motifs, and one comprised by the T region.

In Chapter 3 the subcellular localization of AVR1 and R1 was investigated. Both were demonstrated to be nucleocytoplasmic proteins. We artificially modified the nucleocytoplasmic partitioning of AVR1 and R1 using nuclear localization and export signals (NLS/NES), and studied the effect on R1-AVR1 recognition. This revealed that nuclear localization of both AVR1 and R1 is important to induce R1-mediated immunity. In addition, we showed that AVR1-mediated suppression of CRN2-induced cell death is dependent on cytosolic localization of AVR1.

In Chapter 4, we investigated how AVR1 modulates host defense. In a yeast two-hybrid screening we identified the exocyst subunit Sec5 as a host target for AVR1. Interaction between AVR1 and Sec5 was confirmed in planta by co-immunoprecipitation and bimolecular fluorescent complementation. Although A-L shares high sequence similarity with AVR1, we found that it is not able to interact with Sec5. Sec5 was shown to be required for proper plant defense against P. infestans. The role of Sec5 in plant response upon pathogen attack was further supported by its role in callose deposition and in secretion of the pathogenesis-related protein PR-1, which indicates that Sec5 plays a crucial role in vesicle trafficking during host defense. AVR1 is able to suppress callose deposition while A-L is not, which suggests that P. infestans manipulates host vesicle trafficking by secretion of AVR1 to target Sec5. Overall, our findings unravelled a novel strategy that oomycete pathogens exploit in order to modulate host defense.

In Chapter 5 we further analysed the potential virulence activities of AVR1 and A-L. Both AVR1 and A-L were able to promote P. infestans colonization, indicating that both are genuine P. infestans virulence factors. Moreover, AVR1 was found to suppress not only callose deposition, but also Sec5-dependent cell death induced by the P. infestans elicitors INF1 and CRN2. In contrast, A-L was neither able to suppress Sec5-dependent nor Sec5-independent cell death. The conserved C-terminal motifs and regions required for virulence activity of AVR1 were investigated using AVR1 truncated constructs. In addition, the conserved C-terminal motifs and regions of AVR1 required for Sec5 interaction were studied by Y2H assays. Although the T-region of AVR1 was found to be sufficient to facilitate P. infestans colonization and suppression of CRN2-induced cell death, it could not fully accommodate the interaction of AVR1 with Sec5. Instead, both the Y motif and the T-region of AVR1 appear to be required for Sec5 targeting.

Next to Sec5, the role of other exocyst subunits in Phytophthora resistance was studied (Chapter 6). The evolutionary relationships of exocyst subunits from three Solanaceous plants, i.e. Nicotiana benthamiana, tomato and potato, were investigated in comparison to their Arabidopsis orthologs. Virus-induced gene silencing in N. benthamiana of the majority of the exocyst subunit genes (exo84s were not yet included) showed that, except for some Exo70 members, all other tested exocyst subunits are required for plant defense against P. infestans and callose deposition. In addition, all of the analysed exocyst subunit gene-silenced tomato plants showed gain of susceptibility to both P. infestans and Phytophthora capsici.

In Chapter 7, our findings obtained in this thesis on the mechanisms of AVR1-triggered host immunity and susceptibility are discussed in a broader perspective with emphasis on the current developments in the field of effector biology.

Cisgenese drukt kosten phytophthorabestrijding
Kessel, G.J.T. - \ 2014
Boerderij 99 (2014)49. - ISSN 0006-5617 - p. 61 - 61.
akkerbouw - aardappelen - gewasbescherming - genetische gewasbescherming - resistentie van variëteiten - phytophthora infestans - plantenveredeling - cisgenese - kosten - opbrengst - veldproeven - arable farming - potatoes - plant protection - genetic control - varietal resistance - plant breeding - cisgenesis - costs - outturn - field tests
Wageningen UR test op aardappelen die via cisgenese zijn voorzien van een of meer genen, die ze beter bestand maken tegen phytophthora. Bij cisgenese worden soorteigen genen uit wilde aardappelplanten gebruikt. (Bij transgenese gaat het om soortvreemde genen.)
The discursive other dynamics in plant scientists' talk on Phytophthora with experts and the public
Mogendorff, K.G. - \ 2014
University. Promotor(en): Cees van Woerkum; Bart Gremmen, co-promotor(en): Hedwig te Molder. - Wageningen : Wageningen University - ISBN 9789462570467 - 150 p.
communicatie - genetische modificatie - planten - technologie - discoursanalyse - openbare mening - genomica - plantkunde - wetenschappers - deskundigen - phytophthora infestans - discussie - antropologie - psychologie - communication - genetic engineering - plants - technology - discourse analysis - public opinion - genomics - botany - scientists - experts - discussion - anthropology - psychology
This dissertation investigates the interactional effects of Dutch plant science experts' talk in different interaction settings: public meetings, expert board meetings and ethnographic interviews. The main research approach deployed is discursive psychology : a methodology that focuses not on what is said but on what is accomplished with talk. The central topic of all the talk analysed in this thesis is Phytophthora Infestans: a major plant disease in staple crops that helped bring about the Irish famine in the 19th century. Phytophthora is still a large problem. To fight Phytophthora, plant experts have been developing different technologies, some of which, such as genetic modification, are met with public controversy.
Participatory potato breeding model involving organic farmers and commercial breeding companies in the Netherladns
Lammerts Van Bueren, E. ; Engelen, C.J.M. ; Hutten, R.C.B. - \ 2014
In: Proceedings of the 7th Organic Seed Growers Conference. - - p. 69 - 73.
biologische plantenveredeling - aardappelen - cultivars - phytophthora infestans - biologische landbouw - akkerbouw - organic plant breeding - potatoes - organic farming - arable farming
Organic farmers urgently need cultivars resistant to Phytophthora infestans. Such cultivars also need to be adapted to other traits important for organic farming systems. One goal in the first five years of this ten-year, public-private partnership was to establish a program within the Dutch potato breeding system that includes farmer breeders working in close collaboration with six commercial breeding companies and two research institutes. To meet the goals we have involved 14 organic farmer breeders through setting up a yearly breeding course. A pre-breeding program is now running to introgress late blight resistance from wild relatives into cultivated material, and to make crossings with advances genitors to distribute seeds to farmer and commercial breeders for selection. In this paper a short overview is given of the results of 2009-2013.
Elicitin-triggerd apoplastic immunity against late blight in potato
Du, J. - \ 2014
University. Promotor(en): Richard Visser; Evert Jacobsen, co-promotor(en): Vivianne Vleeshouwers. - Wageningen : Wageningen University - ISBN 9789462570092 - 140 p.
solanum tuberosum - aardappelen - plantenziekteverwekkende schimmels - phytophthora infestans - ziekteresistentie - genen - schimmeleiwit - genetische merkers - bio-informatica - plantenveredeling - potatoes - plant pathogenic fungi - disease resistance - genes - fungal protein - genetic markers - bioinformatics - plant breeding
R gene stacking by trans- and cisgenesis to achieve durable late blight resistance in potato
Zhu, S. - \ 2014
University. Promotor(en): Evert Jacobsen; Richard Visser, co-promotor(en): Jack Vossen. - Wageningen : Wageningen University - ISBN 9789461735706 - 164
solanum tuberosum - aardappelen - phytophthora infestans - oömycota - plantenziekteverwekkende schimmels - ziekteresistentie - genen - cisgenese - transgene planten - plantenveredeling - genetische modificatie - potatoes - oomycota - plant pathogenic fungi - disease resistance - genes - cisgenesis - transgenic plants - plant breeding - genetic engineering

Among the many diseases of potato (Solanum tuberosum L.), which is the third food crop in the world after wheat and rice, late blight caused by the oomycete pathogen Phytophthora infestans, is one of the most serious diseases. In the last century, major resistance (R) genes were introgressed mainly from the wild species Solanum demissum into the cultivated potato Solanum tuberosum. However, introgression of late blight resistance genes by interspecific crosses followed by backcrosses, proved to be associated with linkage drag problems. The desired R gene is then closely linked with one or more unfavorable genes. Moreover, the obtained resistance in the varieties could be easily overcome by fast evolving virulence among P.infestans isolates. The introduction of the A2 mating type from Mexico to Europe resulted in genetically more diverse and complex P.infestans offspring, since initially only the A1 mating type existed. Therefore, new strategies for breeding varieties with durable and broad spectrum resistance needed to be developed.

Previous research indicated that varieties containing single major R genes did not show durable resistance. Therefore, the potato breeding and research community abandoned the introgression of major R genes and started breeding for horizontal resistance by combining multiple partial resistance genes. This quantitative resistance breeding approach was also not successful because the levels of resistance were too low, breeding was too complicated and the spectrum was not as broad as anticipated. Nowadays, the introgression of major R genes regained interest and two ways of resistance breeding can be distinguished: 1. molecular marker assisted resistance breeding or 2. genetic modification (GM) of existing varieties with cloned major R genes.

In this thesis, the time-saving GM approach has been investigated to achieve durable resistance against potato late blight in existing varieties by stacking of major R genes via transgenesis and cisgenesis (Chapters 2, 3, 4). These R genes are so called cisgenes and are unmodified copies of genes from the same or crossable species, harboring their own promoter and terminator sequences.

The main difference between cisgenesis and transgenesis is the resulting (end) product. The end products for the latter case are transformants, which contain transgenes, that can come from a very different species, such as the selection marker gene nptII coding for antibiotic resistance from bacteria. However, the end products of cisgenesis, called cisformants, only harbor cisgenes (which are natural genes from the same or crossable species). These cisformants are selected by PCR for the presence of R gene(s) and for the absence of vector backbone sequences. In our study, functionality of the individual R genes, in trans- and cisformants containing stacked R genes, was determined by detached leaf assays (DLA) using avirulent isolates and by agro-infiltration with Avr genes matching every single R gene. Their foliar resistance was also tested in the field, and their resistance in tubers was tested in the lab.

In order to ensure durability, an accurate and robust system must be available to monitor virulence in P.infestans populations. Differential sets with plants containing single R genes are important and developed in many crops in order to facilitate both resistance breeding and genetic research on pathogen populations in different locations worldwide. The existing conventional differential potato set of Mastenbroek was updated and a start was made to develop a GM differential set with cloned R genes in individual transformants of cv Desiree (Chapter 5).

In Chapter 2, R genes with broad and complementary resistance spectrum were selected as a first step for R gene stacking. Selection for these R genes was performed using DLA with 44 selected late blight isolates. Out of four R genes (Rpi-sto1, Rpi-vnt1.1, Rpi-blb3, and R3a), three were selected for stacking experiments, Rpi-sto1 from S. stoloniferum, Rpi-vnt1.1 from S. venturii and Rpi-blb3 from S. bulbocastanum. Cv Desiree transformants containing these three single R genes conferred resistance to 40, 43 and 37 out of 44 isolates, respectively. The R3a containing transformant conferred resistance to only five out of 44 isolates. These three broad spectrum R genes were then combined in one binary vector pBINPLUS containing nptII as kanamycin resistance marker. Transformants containing nptII and the three R genes showed foliar resistance in DLA against two isolates PIC99189 (avrsto1, Avrvnt1, avrblb3) and EC1 (Avrsto1, avrvnt1, Avrblb3). Furthermore, the functions of these three individualR genes were confirmed using the cross reacting Avr genes from the pathogen, since no isolates were available to distinguish the function of each R gene individually due to the broad resistance spectrum. The resistance spectrum of transformants containing the three R genes Rpi-sto1, Rpi-vnt1.1 and Rpi-blb3 showed after DLA the expected sum of resistance spectrum from all three individual R genes and no indications for epistatic effects were observed (Chapter 2). These triple R genes containing transformants showed also full resistance in the field after inoculation with IPO-C (Avrsto1, Avrvnt1, avrblb3) both in 2011 and 2012. Furthermore, these three R genes were inherited to the next generation as a cluster and retained their functionality after crossing. Generally, resistance in tubers of these plants showed also the summed spectrum of all individual R genes in both generations, as was the case in the foliar resistance test. It was remarkable that transgenic Desiree plants, harboring Rpi-sto1 or Rpi-blb3,showed increased resistance in tubers, while their functional homologs Rpi-blb1 and R2, did not show resistance in tubers of conventionally bred materials. The integration of T-DNA borders and vector backbone sequences was also investigated. Around 45% of the triple R gene containing transformants harbored one or two T-DNA copies, without the integration of T-DNA borders and vector backbone (Chapter 3).

The introduction of multiple R genes was also applied to produce cisformants, plants containing only cisgenes. Three approaches were taken: 1) two cisgenes were introduced through one marker free transformation vector, 2) two cisgenes were introduced through two separate marker free vectors by co-transformation, 3) co-transformation of two vectors, one only containing nptII, and the other one is a marker free transformation vector harboring three cisgenes. This co-transformation was followed by sexual crossing to remove selection marker nptII. All three approaches were successful in the production of cisformants. The first approach produced a high percentage (73%) of cisformants but, in contrast to transgenic plants, the percentage of plants showing full resistance in DLA was relatively low (42%). The second approach produced only 4% of cisformants with stacked R genes, due to the high incidence of vector backbone sequence integration from two vectors used for co-transformation. All transformants obtained by the third approach showed full late blight resistance, which was very efficient compared to the first two approaches. This must be due to the use of the nptII selection marker. After crossing, the integration of both T-DNAs appeared to be unlinked in all tested transformants. Therefore, cisformants with active R genes could be obtained. The resistance level in tubers of cisformants was more frequently sufficient in plants with integration of two or more T-DNA copies, as it was also observed in the triple R gene transformants (Chapter 3). Not only the R genes from cisformants obtained using the third approach but also the cisformants from the first approach showed clustered inheritance in a crossing population, while the R genes segregated independently in the crossing population from a cisformant obtained using the second approach (Chapter 4).

The potato late blight differential set is used to characterize the virulence of P.infestans isolates, consisting of eleven plants which are expected to represent eleven different late blight R genes. Most differential plants were found to be susceptible to current late blight isolates, with the exception of the MaR8 and MaR9 plants. It had already been described that additional R genes were present in some members of this differential set. In Chapter 5, all eleven differential plants were tested for a hypersensitive reaction towards seven Avr genes. Only in three differential plants (MaR1, MaR2 and MaR4) no additional R genes were found, while for example MaR3,MaR8 andMaR9 contained multiple R genes. The conventional differential set was extended with F1 and BC1 segregants harboring a reduced number of these R genes and potentially containing only one R gene (R3a, R3b, R8 or R9, respectively) and with plants containing recently cloned R genes (Rpi-blb3, Rpi-sto1, Rpi-blb1, Rpi-pta1, Rpi-blb2, Rpi-vnt1.1 and Rpi-chc1). A disadvantage of the (extended) conventional differential set is that their genetic background is different which is complicating the use of this set. Moreover, for none of the extended differential plants it can be ruled out that different additional R genes are present. Therefore, a GM differential set consisting of ten transformants of cv Desiree, each harboring a single R gene was compiled. This GM differential set is more reliable for characterization of P.infestans isolates and for the functional test of individual R genes, due to the isogenic background. As a proof of concept, the conventional and the GM differential sets were compared using recently collected isolates from Dutch fields in detached leaf assays. It was found that plants containing Rpi-blb3, Rpi-blb1, Rpi-chc1, R8, R9, Rpi-vnt1.1 and Rpi-blb2 showed a broader resistance spectrum as compared to R1, R3a, R3b andR4. Furthermore, the application of the GM differential set to monitor virulence towards the different R genes in local late blight populations using trap fields was investigated. The extended conventional and the GM differential sets are on continuously growing lists, which can be in the future updated with better performing, genetically more isogenic plants harboring novel R genes, or when new R genes are transformed into cv Desiree.

In the general discussion (chapter 6), related topics from different experimental chapters are discussed simultaneously, some additional experimental data are provided and a broader view on the research area is given.

In summary, five main conclusions can be drawn from this work: 1. broad spectrum resistance in leaf and tuber with stable inheritance can be achieved by gene stacking via transgenesis and cisgenesis; 2. The frequency of cisformants with sufficient resistance at foliage and tuber level is lower than in transformants; 3. Avr genes are highly needed to test for functionality of all stacked R genes in trans- or cisformants; 4. the GM differential set can be used to accurately characterize P.infestans isolates and to assess the employability of certain R genes in particular geographic locations; and 5. genetic transformation is a unique way to improve existing susceptible potato varieties such as the cvs Bintje and Russet Burbank which are grown at relatively large areas worldwide.

Jaarrond bestrijdingsstrategie Phytophthora
Schepers, H.T.A.M. ; Evenhuis, B. - \ 2014 2014 (2014)28 juli.
akkerbouw - gewasbescherming - phytophthora infestans - aardappelen - pootaardappelen - fabrieksaardappelen - ziektebestrijding - consumptieaardappelen - plantenziektebestrijding - ziektepreventie - arable farming - plant protection - potatoes - seed potatoes - starch potatoes - disease control - table potatoes - plant disease control - disease prevention
Voorkomen is beter dan genezen. Dit geldt bij uitstek voor de aardappelziekte, veroorzaakt door Phytophthtora infestans. Het uitgangspunt voor de Phytophthora-bestrijdingsstrategie is het stapelen van zoveel mogelijk preventieve maatregelen, indien noodzakelijk aangevuld met curatieve maatregelen. Dit geeft, over het hele seizoen bekeken, de meest (kosten)effectieve en minst milieubelastende beheersing van de aardappelziekte in de zetmeel-, poot- en consumptieaardappelteelt.
Technologiestijlen in de aardappelteelt : mogelijkheden voor een breder innovatiebeleid
Ruivenkamp, G.T.P. - \ 2013
Wageningen : Wageningen Universiteit, Sociologie en Antropologie van Ontwikkeling - 21
akkerbouw - aardappelen - veldgewassen - gewasbescherming - chemische bestrijding - milieueffect - innovaties - maatschappelijk verantwoord ondernemen - beleidsonderzoek - phytophthora infestans - arable farming - potatoes - field crops - plant protection - chemical control - environmental impact - innovations - corporate social responsibility - policy research
Oriënterend onderzoek naar initiatieven van verschillende maatschappelijke organisaties om het bestrijdingsmiddelen gebruik in de aardappelteelt te reduceren
Vergelijkende genoomanalyse geeft inzicht in de evolutie en biologie van pathogene oömyceten
Seidl, M.F. ; Govers, F. - \ 2013
Gewasbescherming 44 (2013)4. - ISSN 0166-6495 - p. 109 - 112.
genomica - oömyceten - pathogenen - biologie - evolutie - moleculaire genetica - plantenziekteverwekkende schimmels - bio-informatica - plantenziekten - phytophthora infestans - genomics - oomycetes - pathogens - biology - evolution - molecular genetics - plant pathogenic fungi - bioinformatics - plant diseases
Hoewel oömyceten nog maar kortgeleden het genomica-tijdperk zijn binnengetreden hebben de nieuwe ‘-omics’-technieken al geleid tot een overvloed aan kwantitatieve data. Vergelijkende en geïntegreerde genomica is cruciaal om deze schatkist met data te ontsluiten. In het proefschrift ‘Exploring Evolution and Biology of Oomycetes: Integrative and Comparative Genomics’ zijn met succes de eerste stappen gezet om deze data te gebruiken om zodoende de evolutie en biologie van oömyceten verder te ontrafelen en dit heeft reeds geleid tot waardevole nieuwe inzichten.
Green breeding : bioimpuls programme 2009-2013: perspectives on Phytophthora-resistant potato varieties
Scholten, O.E. ; Lammerts Van Bueren, E. - \ 2013
Wageningen UR etc.
biologische plantenveredeling - plantenveredeling - resistentieveredeling - aardappelen - phytophthora infestans - genetisch bepaalde resistentie - onderzoeksprojecten - biologische landbouw - akkerbouw - organic plant breeding - plant breeding - resistance breeding - potatoes - genetic resistance - research projects - organic farming - arable farming
The heavy outbreaks of Phytophthora in 2007, and again in 2012, reconfirmed the need for resistant potato varieties for the organic sector. Until recently no such varieties were available. In 2009 the Bioimpulsprogramme was launched to give more priority to breeding organic, Phytophthora-resistant varieties. In this 10-year programme, wild potato species are crossed with cultivated potato to develop new resistant varieties. Although this classical breeding strategy is a long road, the advantage is that you can select for multiple traits along the way. This brochure presents the results of the first four years of the programme.
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