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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    OsJAR1 is required for JA-regulated floret opening and anther dehiscence in rice
    Xiao, Y. ; Charnikhova, T. ; Mulder, P.P.J. ; Heijmans, J. ; Hoogenboom, A. ; Agalou, A. ; Michel, C. ; Morel, J.B. ; Dreni, L. ; Kater, M.M. ; Bouwmeester, H.J. ; Wang, B. ; Zhu, Z. ; Ouwerkerk, P.B.F. - \ 2014
    Plant Molecular Biology 86 (2014)1-2. - ISSN 0167-4412 - p. 19 - 33.
    jasmonic acid biosynthesis - male-sterile mutant - l-isoleucine - methyl jasmonate - gene encodes - arabidopsis - enzyme - proteins - tomato - (+)-7-iso-jasmonoyl-l-isoleucine
    Jasmonates are important phytohormones regulating reproductive development. We used two recessive rice Tos17 alleles of OsJAR1, osjar1-2 and osjar1-3, to study the biological function of jasmonates in rice anthesis. The florets of both osjar1 alleles stayed open during anthesis because the lodicules, which control flower opening in rice, were not withering on time. Furthermore, dehiscence of the anthers filled with viable pollen, was impaired, resulting in lower fertility. In situ hybridization and promoter GUS transgenic analysis confirmed OsJAR1 expression in these floral tissues. Flower opening induced by exogenous applied methyl jasmonate was impaired in osjar1 plants and was restored in a complementation experiment with transgenics expressing a wild type copy of OsJAR1 controlled by a rice actin promoter. Biochemical analysis showed that OsJAR1 encoded an enzyme conjugating jasmonic acid (JA) to at least Ile, Leu, Met, Phe, Trp and Val and both osjar1 alleles had substantial reduction in content of JA-Ile, JA-Leu and JA-Val in florets. We conclude that OsJAR1 is a JA-amino acid synthetase that is required for optimal flower opening and closing and anther dehiscence in rice
    Torradoviruses are transmitted in a semi-persistent and stylet-borne manner by three whitefly vectors
    Verbeek, M. ; Bekkum, P.J. van; Dullemans, A.M. ; Vlugt, R.A.A. van der - \ 2014
    Virus Research 186 (2014). - ISSN 0168-1702 - p. 55 - 60.
    plant-virus transmission - picorna-like virus - bemisia-tabaci - tomato - aleyrodidae - efficiency - diseases
    Members of the genus Torradovirus (family Secoviridae, type species Tomato torrado virus, ToTV) are spherical plant viruses transmitted by the whitefly species Trialeurodes vaporariorum and Bemisia tabaci. Knowledge on the mode of vector transmission is lacking for torradoviruses. Here, the mode of transmission was determined for Tomato marchitez virus (ToMarV). A minimal acquisition access period (AAP) and inoculation access period (IAP) of approximately 2h each was required for its transmission by T. vaporariorum, while optimal transmission required an AAP and IAP of at least 16h and 8h, respectively. Whiteflies could retain the virus under non-feeding conditions for at least 8h without loss of transmission efficiency, but upon feeding on a non-host plant in between the AAP and IAP they retained the virus for no more than 8h. Similar conditions supported transmission of isolates of ToTV and Tomato chocolàte virus (ToChV) by T. vaporariorum and B. tabaci. Additionally, similar experiments revealed the banded-winged whitefly (Trialeurodes abutilonea) as a vector for all three virus species. The results are congruent with acquisition and retention periods for semi-persistent virus transmission. RT-PCR detection analysis of ToTV and ToMarV in the vector's body revealed their presence in the stylet, but not in the head where the pharynx of the foregut is located. The results altogether indicate a semi-persistent stylet-borne mode of vector transmission for torradoviruses. Additionally, this is the first group of spherical viruses transmitted by at least three different species of whiteflies
    Development of late blight resistant potatoes by cisgenic stacking
    Jo, K.R. ; Kim, C.J. ; Kim, S.J. ; Kim, T.J. ; Bergervoet-van Deelen, J.E.M. ; Jongsma, M.A. ; Visser, R.G.F. ; Jacobsen, E. ; Vossen, J.H. - \ 2014
    BMC Biotechnology 14 (2014). - ISSN 1472-6750
    broad-spectrum resistance - cultivar sarpo mira - phytophthora-infestans - solanum-bulbocastanum - r-gene - plants - transformation - genomics - tomato - biotechnology
    Background Phytophthora infestans, causing late blight in potato, remains one of the most devastating pathogens in potato production and late blight resistance is a top priority in potato breeding. The introduction of multiple resistance (R) genes with different spectra from crossable species into potato varieties is required. Cisgenesis is a promising approach that introduces native genes from the crops own gene pool using GM technology, thereby retaining favourable characteristics of established varieties. Results We pursued a cisgenesis approach to introduce two broad spectrum potato late blight R genes, Rpi-sto1 and Rpi-vnt1.1 from the crossable species Solanum stoloniferum and Solanum venturii, respectively, into three different potato varieties. First, single R gene-containing transgenic plants were produced for all varieties to be used as references for the resistance levels and spectra to be expected in the respective genetic backgrounds. Next, a construct containing both cisgenic late blight R genes (Rpi-vnt1.1 and Rpi-sto1), but lacking the bacterial kanamycin resistance selection marker (NPTII) was transformed to the three selected potato varieties using Agrobacterium-mediated transformation. Gene transfer events were selected by PCR among regenerated shoots. Through further analyses involving morphological evaluations in the greenhouse, responsiveness to Avr genes and late blight resistance in detached leaf assays, the selection was narrowed down to eight independent events. These cisgenic events were selected because they showed broad spectrum late blight resistance due to the activity of both introduced R genes. The marker-free transformation was compared to kanamycin resistance assisted transformation in terms of T-DNA and vector backbone integration frequency. Also, differences in regeneration time and genotype dependency were evaluated. Conclusions We developed a marker-free transformation pipeline to select potato plants functionally expressing a stack of late blight R genes. Marker-free transformation is less genotype dependent and less prone to vector backbone integration as compared to marker-assisted transformation. Thereby, this study provides an important tool for the successful deployment of R genes in agriculture and contributes to the production of potentially durable late blight resistant potatoes.
    Relocation of genes generates non-conserved chromosomal segments in Fusarium graminearum that show distinct and co-regulated gene expression patterns
    Zhao, C. ; Waalwijk, C. ; Wit, P.J.G.M. de; Tang, D. ; Lee, T.A.J. van der - \ 2014
    BMC Genomics 15 (2014). - ISSN 1471-2164 - 17 p.
    polyketide synthase genes - gibberella-zeae - rna-seq - oxysporum - evolution - reveals - resistance - virulence - tomato - yeast
    BACKGROUND: Genome comparisons between closely related species often show non-conserved regions across chromosomes. Some of them are located in specific regions of chromosomes and some are even confined to one or more entire chromosomes. The origin and biological relevance of these non-conserved regions are still largely unknown. Here we used the genome of Fusarium graminearum to elucidate the significance of non-conserved regions. RESULTS: The genome of F. graminearum harbours thirteen non-conserved regions dispersed over all of the four chromosomes. Using RNA-Seq data from the mycelium of F. graminearum, we found weakly expressed regions on all of the four chromosomes that exactly matched with non-conserved regions. Comparison of gene expression between two different developmental stages (conidia and mycelium) showed that the expression of genes in conserved regions is stable, while gene expression in non-conserved regions is much more influenced by developmental stage. In addition, genes involved in the production of secondary metabolites and secreted proteins are enriched in non-conserved regions, suggesting that these regions could also be important for adaptations to new environments, including adaptation to new hosts. Finally, we found evidence that non-conserved regions are generated by sequestration of genes from multiple locations. Gene relocations may lead to clustering of genes with similar expression patterns or similar biological functions, which was clearly exemplified by the PKS2 gene cluster. CONCLUSIONS: Our results showed that chromosomes can be functionally divided into conserved and non-conserved regions, and both could have specific and distinct roles in genome evolution and regulation of gene expression
    Lettuce necrotic leaf curl virus, a new plant virus infecting lettuce and a proposed member of the genus Torradovirus
    Verbeek, M. ; Dullemans, A.M. ; Raaij, H.M.G. van; Verhoeven, J.Th.J. ; Vlugt, R.A.A. van der - \ 2014
    Archives of Virology 159 (2014)4. - ISSN 0304-8608 - p. 801 - 805.
    stranded rna viruses - picorna-like virus - tomato - family
    A new virus was isolated from a lettuce plant grown in an open field in the Netherlands in 2011. This plant was showing conspicuous symptoms that consisted of necrosis and moderate leaf curling. The virus was mechanically transferred to indicator plants, and a total RNA extract of one of these indicator plants was used for next-generation sequencing. Analysis of the sequences that were obtained and further biological studies showed that the virus was related to, but clearly distinct from, viruses belonging to the genus Torradovirus. The name “lettuce necrotic leaf curl virus” (LNLCV) is proposed for this new torrad
    Positive selection and intragenic recombination contribute to high allelic diversity in effector genes of Mycosphaerella fijiensis, causal agent of the black leaf streak disease of banana
    Stergiopoulos, I. ; Cordovez da Cunha, V. ; Okmen, B. ; Beenen, H.G. ; Kema, G.H.J. ; Wit, P.J.G.M. de - \ 2014
    Molecular Plant Pathology 15 (2014)5. - ISSN 1464-6722 - p. 447 - 460.
    pathogen cladosporium-fulvum - phylogenetic analysis - musa-acuminata - cf-4-mediated resistance - population-genetics - maximum-likelihood - evolution - proteins - fungal - tomato
    Previously, we have determined the nonhost-mediated recognition of the MfAvr4 and MfEcp2 effector proteins from the banana pathogen Mycosphaerella fijiensis in tomato, by the cognate Cf-4 and Cf-Ecp2 resistance proteins, respectively. These two resistance proteins could thus mediate resistance against M.¿fijiensis if genetically transformed into banana (Musa spp.). However, disease resistance controlled by single dominant genes can be overcome by mutated effector alleles, whose products are not recognized by the cognate resistance proteins. Here, we surveyed the allelic variation within the MfAvr4, MfEcp2, MfEcp2-2 and MfEcp2-3 effector genes of M.¿fijiensis in a global population of the pathogen, and assayed its impact on recognition by the tomato Cf-4 and Cf-Ecp2 resistance proteins, respectively. We identified a large number of polymorphisms that could reflect a co-evolutionary arms race between host and pathogen. The analysis of nucleotide substitution patterns suggests that both positive selection and intragenic recombination have shaped the evolution of M.¿fijiensis effectors. Clear differences in allelic diversity were observed between strains originating from South-East Asia relative to strains from other banana-producing continents, consistent with the hypothesis that M.¿fijiensis originated in the Asian-Pacific region. Furthermore, transient co-expression of the MfAvr4 effector alleles and the tomato Cf-4 resistance gene, as well as of MfEcp2, MfEcp2-2 and MfEcp2-3 and the putative Cf-Ecp2 resistance gene, indicated that effector alleles able to overcome these resistance genes are already present in natural populations of the pathogen, thus questioning the durability of resistance that can be provided by these genes in the field.
    Cloning and functional characterization of the Rvi15 (Vr2) gene for apple scab resistance
    Schouten, H.J. ; Brinkhuis, J. ; Burgh, S. van der; Schaart, J. ; Groenwold, R. ; Broggini, G.A.L. ; Gessler, C. - \ 2014
    Tree Genetics and Genomes 10 (2014)2. - ISSN 1614-2942 - p. 251 - 260.
    malus x domestica - venturia-inaequalis - cladosporium-fulvum - cisgenic plants - plasma-membrane - vf gene - tomato - locus - proteins - pathogen
    Apple scab, caused by Venturia inaequalis, is a serious disease of apple. Previously, the scab resistance Rvi15 (Vr2) from the accession GMAL 2473 was genetically mapped, and three candidate resistance genes were identified. Here, we report the cloning and functional characterization of these three genes, named Vr2-A, Vr2-B, and Vr2-C. Each gene was cloned with its native promoter, terminator and introns, and inserted into the susceptible apple cultivar ‘Gala’. Inoculation of the plants containing Vr2-A and Vr2-B induced no resistance symptoms, but abundant sporulation. However, inoculation of the plants harboring Vr2-C showed a hypersensitive response with clear pinpoint pits, and no or very little sporulation. We conclude that Vr2-C is the Rvi15 (Vr2) gene. This gene belongs to the Toll and mammalian interleukin-1 receptor protein nucleotide-binding site leucine-rich repeat structure resistance gene family. The proteins of this gene family reside in the cytoplasm, whereas V. inaequalis develops in the apoplast, between the epidermis and cuticle, without making haustoria. The spatial separation of the recognizing resistance protein and the pathogen is discussed. This is the second cloned gene for apple scab resistance, and out of these two the only one leading to a symplastic protein.
    Genetic mapping of gummy stem blight (Didymella bryoniae) resistance genes in Cucumis sativus-hystrix introgression lines
    Lou, L. ; Wang, H.Y. ; Qian, C.T. ; Liu, J. ; Bai, Y. ; Chen, J.F. - \ 2013
    Euphytica 192 (2013)3. - ISSN 0014-2336 - p. 359 - 369.
    interspecific hybridization - north-carolina - field-tests - genome - rearrangements - cucurbitaceae - tomato - crops - leaf - dna
    Gummy stem blight (GSB, Didymella bryoniae (Auersw.) Rehm) is a devastating disease occurring worldwide in cucumber (Cucumis sativus L.) production and causing considerable yield loss. No commercially available cultivars are resistant to GSB. By screening 52 introgression lines (ILs) derived from the cross of C. hystrix x C. sativus and eight cucumber cultivar/lines through a whole plant assay, three ILs (HH1-8-1-2, HH1-8-5, HH1-8-1-16) were identified as GSB resistant lines. Six common introgression regions in these three ILs were on Chromosomes 1, 4, and 6. To further map the resistance in the ILs, three mapping populations (2009F(2), 2009F(2)' and 2010F(2)) from a cross between resistant IL HH1-8-1-2 and susceptible 8419 were constructed and used for QTL mapping with SSR markers. Two quantitative trait loci (QTLs) were identified; one on Chromosome 4 and the other on Chromosome 6. The interval for Chromosome 4 QTL is 12 cM spanning 3.569 Mbp, and the interval for Chromosome 6 QTL is 11 cM covering 1.299 Mbp. The mapped QTLs provide a foundation for map-based cloning of the genes and establishing an understanding of the associated mechanisms underlying GSB resistance in cucumber.
    Feeding behaviour and performance of different populations of the black currant-lettuce aphid, Nasonovia ribisnigri, on resistant and susceptible lettuce
    Broeke, C.J.M. ten; Dicke, M. ; Loon, J.J.A. van - \ 2013
    Entomologia Experimentalis et Applicata 148 (2013)2. - ISSN 0013-8703 - p. 130 - 141.
    host-plant resistance - myzus-persicae - potato aphid - tissue localization - lactuca-sativa - gene mi - tomato - leaf - homoptera - biotypes
    When crops are bred for resistance to herbivores, these herbivores are under strong selection pressure to overcome this resistance, which may result in the emergence of virulent biotypes. This is a growing problem for crop species attacked by aphids. The Nr-gene in lettuce confers near-complete resistance against the black currant-lettuce aphid, Nasonovia ribisnigri (Mosely) (Hemiptera: Aphididae). Since 2007, populations of N.ribisnigri have been reported in several locations in Europe to infest resistant lettuce varieties that possess the Nr-gene. The objective of this study was to analyse the behaviour and level of virulence of several N.ribisnigri populations observed to have colonized Nr-locus-containing lettuce lines. We analysed the stylet penetration and feeding behaviour, and the performance of these N.ribisnigri populations on resistant and susceptible lettuce lines. Large variation in the degree of virulence to the Nr-locus-containing lettuce lines was found among populations of the Nr:1 biotype. The German population was highly virulent on the Nr-containing resistant lettuce lines, and showed similar feeding behaviour and performance on both the susceptible and resistant lettuces. The French population from Paris was the second most virulent, though reproduction on the resistant lines was reduced. The French population from Perpignan and a population from Belgium, however, showed reduced performance and feeding rate on the resistant compared to the susceptible lettuces. The lettuce background in which the Nr-gene is expressed influences the level of resistance to the various Nr:1 aphid populations, because the performance and feeding behaviour differed between the aphids on the cultivars (romaine lettuce) compared to the near-isogenic lines (butterhead/iceberg lettuce). This study also shows that being able to feed on a plant not automatically implies that a population can successfully develop on that plant, because aphids showed phloem ingestion during the 8-h recording period on resistant lettuce, but were not able to survive and reproduce on the same lettuce line.
    Genomic analysis of the native European Solanum species, S. dulcamara
    Agostino, N.D. ; Golas, T. ; Geest, H. van; Bombarely, A. ; Dawood, T. ; Zethof, J. ; Driedonks, N. ; Wijnker, T.G. ; Bargsten, J. ; Nap, J.P. ; Mariani, C. ; Rieu, I. - \ 2013
    BMC Genomics 14 (2013). - ISSN 1471-2164 - 14 p.
    phytophthora-infestans - solanaceae - identification - evolution - polymorphism - sequence - tomato - potato - genes
    Background - Solanum dulcamara (bittersweet, climbing nightshade) is one of the few species of the Solanaceae family native to Europe. As a common weed it is adapted to a wide range of ecological niches and it has long been recognized as one of the alternative hosts for pathogens and pests responsible for many important diseases in potato, such as Phytophthora. At the same time, it may represent an alternative source of resistance genes against these diseases. Despite its unique ecology and potential as a genetic resource, genomic research tools are lacking for S. dulcamara. We have taken advantage of next-generation sequencing to speed up research on and use of this non-model species. Results - In this work, we present the first large-scale characterization of the S. dulcamara transcriptome. Through comparison of RNAseq reads from two different accessions, we were able to predict transcript-based SNP and SSR markers. Using the SNP markers in combination with genomic AFLP and CAPS markers, the first genome-wide genetic linkage map of bittersweet was generated. Based on gene orthology, the markers were anchored to the genome of related Solanum species (tomato, potato and eggplant), revealing both conserved and novel chromosomal rearrangements. This allowed a better estimation of the evolutionary moment of rearrangements in a number of cases and showed that chromosomal breakpoints are regularly re-used. Conclusion - Knowledge and tools developed as part of this study pave the way for future genomic research and exploitation of this wild Solanum species. The transcriptome assembly represents a resource for functional analysis of genes underlying interesting biological and agronomical traits and, in the absence of the full genome, provides a reference for RNAseq gene expression profiling aimed at understanding the unique biology of S. dulcamara. Cross-species orthology-based marker selection is shown to be a powerful tool to quickly generate a comparative genetic map, which may speed up gene mapping and contribute to the understanding of genome evolution within the Solanaceae family.
    Changes in sour cherry (Prunus cerasus L.) antioxidants during nectar processing and in vitro gastrointestinal digestion.
    Toydemir, G. ; Capanoglu, E. ; Kamiloglu, S. ; Boyacioglu, D. ; Vos, C.H. de; Hall, R.D. ; Beekwilder, M.J. - \ 2013
    Journal of Functional Foods 5 (2013)3. - ISSN 1756-4646 - p. 1402 - 1413.
    phenolic-compounds - vitamin-c - anthocyanins - extract - tomato - degradation - metabolome - capacities - cultivars - stability
    Sour cherry (Prunus cerasus L.) is rich in polyphenols, and like its processed products, is especially rich in anthocyanins. We have applied HPLC, spectrophotometric and on-line antioxidant detection methods to follow the fate of cherry antioxidants during an entire multi-step industrial-scale processing strategy. This was performed for 22 sampling points, with five independent repeats from a commercial cherry nectar production process. Anthocyanins contributed to >50% of the total antioxidant capacity of the samples. An in vitro gastrointestinal (GI) digestion system was used to investigate serum availability of antioxidants. In this system anthocyanin bioavailability was much higher in the processed nectar than in the fresh fruit. Together these results indicate that processed sour cherry nectar is a rich source of stable antioxidants with high bioavailability, auguring well for the potential health-promoting capacity of sour cherry products.
    Biosynthesis of Antinutritional Alkaloids in Solanaceous Crops Is Mediated by Clustered Genes
    Itkin, M. ; Heinig, U. ; Tzfadia, O. ; Bhide, A.J. ; Shinde, B. ; Cardenas, P.D. ; Bocobza, S.E. ; Unger, T. ; Malitsky, S. ; Finkers, H.J. ; Tikunov, Y.M. ; Bovy, A.G. ; Chikate, Y. ; Singh, P. ; Rogachev, I. ; Beekwilder, J. ; Giri, A.P. ; Aharoni, A. - \ 2013
    Science 341 (2013)6142. - ISSN 0036-8075 - p. 175 - 179.
    glycoalkaloids - potato - plant - metabolites - pathways - saponins - tomato
    Steroidal glycoalkaloids (SGAs) such as a-solanine found in solanaceous food plants—as, for example, potato—are antinutritional factors for humans. Comparative coexpression analysis between tomato and potato coupled with chemical profiling revealed an array of 10 genes that partake in SGA biosynthesis. We discovered that six of them exist as a cluster on chromosome 7, whereas an additional two are adjacent in a duplicated genomic region on chromosome 12. Following systematic functional analysis, we suggest a revised SGA biosynthetic pathway starting from cholesterol up to the tetrasaccharide moiety linked to the tomato SGA aglycone. Silencing GLYCOALKALOID METABOLISM 4 prevented accumulation of SGAs in potato tubers and tomato fruit. This may provide a means for removal of unsafe, antinutritional substances present in these widely used food crops.
    Industrial processing effects on phenolic compounds in sour cherry (Prunus cerasus L.) fruit
    Toydemir, G. ; Capanoglu, E. ; Gomez-Roldan, M.V. ; Vos, R.C.H. de; Boyacioglu, D. ; Hall, R.D. ; Beekwilder, M.J. - \ 2013
    Food Research International 53 (2013)1. - ISSN 0963-9969 - p. 218 - 225.
    anthocyanins - tomato - tool - polyphenolics - metabolomics
    The processed juice (or nectar) of the sour cherry, Prunus cerasus L., is widely consumed in the Balkan region and Turkey. Sour cherry is known to be rich in polyphenolic compounds, such as anthocyanins and procyanidins. In this work, the effects of processing of sour cherry fruit to nectar on polyphenolic compounds was studied. From a Turkish industrial nectar production factory, five fruit batches were sampled during the processing from fruit to nectar, and for each batch 22 sampling points in the process were investigated. Untargeted LC–MS analysis revealed 193 compounds in sour cherry, of which 38 could be putatively identified. Only seven compounds were affected by the process from fruit to nectar, among which were five phenolic compounds. Waste residues such as press cake contained hardly any anthocyanins, while 87% of the major fruit anthocyanin, cyanidin-3-(2G-glucosylrutinoside), was found in the final nectar. In contrast, procyanidins showed a lower recovery (62%), and were still well represented in the discarded press cake. In comparison with other fruit juices, the recovery of anthocyanins in sour cherry nectar is remarkably high.
    Phenotypic, Molecular, and Pathological Characterization of Colletotrichum acutatum Associated with Andean Lupine and Tamarillo in the Ecuadorian Andes
    Falconi, C. ; Visser, R.G.F. ; Heusden, A.W. van - \ 2013
    Plant Disease 97 (2013)6. - ISSN 0191-2917 - p. 819 - 827.
    phytophthora-infestans - phylogenetic-relationships - olive anthracnose - ribosomal dna - sensu-lato - strawberry - identification - diversity - gloeosporioides - tomato
    Anthracnose is a serious problem of both Andean lupine and tamarillo in Ecuador. Morphological features, internal transcribed spacer (ITS) sequences, and host specificity were used to characterize Colletotrichum isolates from lupine and tamarillo. Based on phenotypic and molecular characterization, the causal agent of anthracnose on both hosts was Colletotrichum acutatum. All isolates were identified in a C. acutatum-specific polymerase chain reaction assay. Colony diameter, conidia shape, and insensitivity to benomyl also placed isolates from both hosts in the C. acutatum group. However, a detailed analysis of the ITS sequences placed the lupine and tamarillo isolates from the Ecuadorian Andean zone in two clades, with both lupine and tamarillo isolates in each clade. C. acutatum isolates from Andean lupine were distinct from other C. acutatum isolates on lupine around the world. In cross-infection studies, the diameter of lesions produced by isolates from each host was compared on the main stem of two tamarillo and three lupine cultivars. Some isolates produced larger lesions on the host from which they were isolated but others showed similar aggressiveness on their alternate host. Isolates from both hosts were biotrophic on lupine stems, producing little necrosis and abundant sporulation whereas, on tamarillo stems, they produced dark lesions with few conidia. The collection of C. acutatum isolates from lupine and tamarillo provides interesting material for the study quantitative host adaptation.
    The efficiency of drip irrigation unpacked
    Kooij, S. van der; Zwarteveen, M.Z. ; Boesveld, H. ; Kuper, M. - \ 2013
    Agricultural Water Management 123 (2013). - ISSN 0378-3774 - p. 103 - 110.
    water-use efficiency - furrow irrigation - surface irrigation - root distribution - cotton yield - fruit yield - productivity - soil - l. - tomato
    Drip irrigation figures prominently in water policy debates as a possible solution to water scarcity problems, based on the assertion that it will improve water use efficiencies. We use this article to carefully trace the scientific basis of this assertion. Through a systematic review of the literature, we show that the term efficiency means different things to different people, and can refer to different elements in the water balance. Most articles claim that drip irrigation is irrigation water use efficient and crop water use efficient, but different studies use different definitions of these terms. In addition, measured efficiency gains not only refer to different capacities of the technology, but are also based on very specific boundary (scale) assumptions. We conclude that efficiency gains from drip irrigation will only be achieved under narrowly defined operational conditions, and just apply to very specific spatial and temporal scales. Hence, and unlike what generalized statements in policy documents and the overall enthusiasm for drip as a water saving tool suggest, expectations of increased water efficiencies associated with drip will only be realized, and are just realizable, in very specific circumstances.
    Physiological and morphological changes during early and later stages of fruit growth in Capsicum annuum
    Tiwari, A. ; Vivian-Smith, A. ; Ljung, K. ; Offringa, R. ; Heuvelink, E. - \ 2013
    Physiologia Plantarum 147 (2013)3. - ISSN 0031-9317 - p. 396 - 406.
    polar auxin transport - cell expansion - sweet-pepper - sink strength - tomato - arabidopsis - set - endoreduplication - fertilization - parthenocarpy
    Fruit-set involves a series of physiological and morphological changes that are well described for tomato and Arabidopsis, but largely unknown for sweet pepper (Capsicum annuum). The aim of this paper is to investigate whether mechanisms of fruit-set observed in Arabidopsis and tomato are also applicable to C. annuum. To do this, we accurately timed the physiological and morphological changes in a post-pollinated and un-pollinated ovary. A vascular connection between ovule and replum was observed in fertilized ovaries that undergo fruit development, and this connection was absent in unfertilized ovaries that abort. This indicates that vascular connection between ovule and replum is an early indicator for successful fruit development after pollination and fertilization. Evaluation of histological changes in the carpel of a fertilized and unfertilized ovary indicated that increase in cell number and cell diameter both contribute to early fruit growth. Cell division contributes more during early fruit growth while cell expansion contributes more at later stages of fruit growth in C. annuum. The simultaneous occurrence of a peak in auxin concentration and a strong increase in cell diameter in the carpel of seeded fruits suggest that indole-3-acetic acid stimulates a major increase in cell diameter at later stages of fruit growth. The series of physiological and morphological events observed during fruit-set in C. annuum are similar to what has been reported for tomato and Arabidopsis. This indicates that tomato and Arabidopsis are suitable model plants to understand details of fruit-set mechanisms in C. annuum.
    Large subclonal variation in Phytophthora infestans populations associated with Ecuadorian potato landraces
    Delgado, R.A. ; Monteros-Altamiro, A.R. ; Li, Y. ; Visser, R.G.F. ; Lee, T.A.J. van der; Vosman, B. - \ 2013
    Plant Pathology 62 (2013). - ISSN 0032-0862 - p. 1081 - 1088.
    late blight resistance - phenotypic variation - plant-pathogen - mating-type - virulence - diversity - solanum - tomato - genes - variability
    The population of Phytophthora infestans on potato landraces in three provinces (Carchi, Chimborazo and Loja) of Ecuador was analysed. All isolates (n = 66) were of the A1 mating type. Simple sequence repeats (SSR) were used to assess the genetic diversity of the isolates. The P. infestans isolates from the potato landraces grouped in a single clade together with reference isolates belonging to the clonal lineage EC-1. In the 66 SSR profiles obtained, 31 multilocus genotypes were identified. The 66 isolates constituted 49 different races according to the Solanum demissum differential set ( R1 to R11). The P. infestans population was complex and virulent on 4 to 11 R genes. Analysis showed that the subclonal variation in the Ecuadorian EC-1 clone is increasing over time and is much larger than clonal variation in lineages in the Netherlands and Nicaragua, suggesting high mutation rates and little or no selection in Ecuador
    Verticillium dahliae Sge1 differentially regulates expresssion of eandidate effector genes
    Santhanam, P. ; Thomma, B.P.H.J. - \ 2013
    Molecular Plant-Microbe Interactions 26 (2013)2. - ISSN 0894-0282 - p. 249 - 256.
    plant-pathogenic fungi - fusarium-oxysporum - transcriptional regulator - tomato - albicans - virulence - requires - protein - genome - life
    The ascomycete fungus Verticillium dahliae causes vascular wilt diseases in hundreds of dicotyledonous plant species. However, thus far, only few V. dahliae effectors have been identified, and regulators of pathogenicity remain unknown. In this study, we investigated the role of the V. dahliae homolog of Sge1, a transcriptional regulator that was previously implicated in pathogenicity and effector gene expression in Fusarium oxysporum. We show that V. dahliae Sge1 (VdSge1) is required for radial growth and production of asexual conidiospores, because VdSge1 deletion strains display reduced radial growth and reduced conidia production. Furthermore, we show that VdSge1 deletion strains have lost pathogenicity on tomato. Remarkably, VdSge1 is not required for induction of Ave1, the recently identified V. dahliae effector that activates resistance mediated by the Ve1 immune receptor in tomato. Further assessment of the role of VdSge1 in the induction of the nine most highly in-planta-induced genes that encode putative effectors revealed differential activity. Although the expression of one putative effector gene in addition to Ave1 was not affected by VdSge1 deletion, VdSge1 appeared to be required for the expression of six putative effector genes, whereas two of the putative effectors genes were found to be negatively regulated by VdSge1. In conclusion, our data suggest that VdSge1 differentially regulates V. dahliae effector gene expression.
    Population structure of Phytophthora infestans in China – geographic clusters and presence of the EU genotype Blue_13
    Li, Y. ; Lee, T.A.J. van der; Zhu, J.H. ; Jin, G.H. ; Lan, C.Z. ; Zhu, S.X. ; Zhang, R.F. ; Liu, B.W. ; Zhao, Z.J. ; Kessel, G.J.T. ; Huang, S.W. ; Jacobsen, E. - \ 2013
    Plant Pathology 62 (2013)4. - ISSN 0032-0862 - p. 932 - 942.
    potato - diversity - haplotypes - virulence - markers - tomato - dna
    The population structure of Phytophthora infestans in China was studied and three mitochondrial haplotypes (Ia, IIa, IIb) were observed. Genetic analysis with 10 highly informative SSR markers identified 68 different genotypes, including three dominant clonal lineages. In the Chinese P. infestans population, the genotypes were strongly clustered according to their geographic origin. One of dominant clonal lineages was genetically similar to Blue_13, a dominant clonal lineage found in Europe since 2004. This is the first report of Blue_13 outside Europe. Only one mating type (A1) was found in the northern and southeastern provinces, but in southern and northwestern China both mating types were observed. The mating type ratio and SSR allele frequencies indicate that in China the sexual cycle of P. infestans is rare. These results emphasize that the migration of asexual propagules and the generation of subclonal variation are the dominant driving factors of the population structure of P. infestans in China. They may also have implications for the role of monitoring P. infestans populations in potato late blight management strategies in China
    Metabolomics and molecular marker analysis to explore pepper (Capsicum sp.) biodiversity
    Wahyuni, Y. ; Ballester, A.R. ; Tikunov, Y.M. ; Vos, C.H.R. de; Pelgrom, K.T.B. ; Maharijaya, A. ; Sudarmonowati, E. ; Bino, R.J. ; Bovy, A.G. - \ 2013
    Metabolomics 9 (2013)1. - ISSN 1573-3882 - p. 130 - 144.
    acyclic diterpene glycosides - annuum l. - capsaicinoid content - mass-spectrometry - volatile fraction - hs-spme - fruit - tomato - chinense - constituents
    An overview of the metabolic diversity in ripe fruits of a collection of 32 diverse pepper (Capsicum sp.) accessions was obtained by measuring the composition of both semi-polar and volatile metabolites in fruit pericarp, using untargeted LC–MS and headspace GC–MS platforms, respectively. Accessions represented C. annuum, C. chinense, C. frutescens and C. baccatum species, which were selected based on variation in morphological characters, pungency and geographic origin. Genotypic analysis using AFLP markers confirmed the phylogenetic clustering of accessions according to Capsicum species and separated C. baccatum from the C. annuum–C. chinense–C. frutescens complex. Species-specific clustering was also observed when accessions were grouped based on their semi-polar metabolite profiles. In total 88 semi-polar metabolites could be putatively identified. A large proportion of these metabolites represented conjugates of the main pepper flavonoids (quercetin, apigenin and luteolin) decorated with different sugar groups at different positions along the aglycone. In addition, a large group of acyclic diterpenoid glycosides, called capsianosides, was found to be highly abundant in all C. annuum genotypes. In contrast to the variation in semi-polar metabolites, the variation in volatiles corresponded well to the differences in pungency between the accessions. This was particularly true for branched fatty acid esters present in pungent accessions, which may reflect the activity through the acyl branch of the metabolic pathway leading to capsaicinoids. In addition, large genetic variation was observed for many well-established pepper aroma compounds. These profiling data can be used in breeding programs aimed at improving metabolite-based quality traits such as flavour and health-related metabolites in pepper fruits.
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