The battle for chitin recognition in plant-microbe interactions
Sánchez-Vallet, A. ; Mesters, J.R. ; Thomma, B.P.H.J. - \ 2015
FEMS Microbiology Reviews 39 (2015)2. - ISSN 0168-6445 - p. 171 - 183.
receptor-like kinase - medicago-truncatula roots - bacillus-circulans wl-12 - high-affinity binding - fungal cell-wall - nod factor - fusarium-oxysporum - botrytis-cinerea - innate immunity - aspergillus-nidulans
Fungal cell walls play dynamic functions in interaction of fungi with their surroundings. In pathogenic fungi, the cell wall is the first structure to make physical contact with host cells. An important structural component of fungal cell walls is chitin, a well-known elicitor of immune responses in plants. Research into chitin perception has sparked since the chitin receptor from rice was cloned nearly a decade ago. Considering the widespread nature of chitin perception in plants, pathogens evidently evolved strategies to overcome detection, including alterations in the composition of cell walls, modification of their carbohydrate chains and secretion of effectors to provide cell wall protection or target host immune responses. Also non-pathogenic fungi contain chitin in their cell walls and are recipients of immune responses. Intriguingly, various mutualists employ chitin-derived signaling molecules to prepare their hosts for the mutualistic relationship. Research on the various types of interactions has revealed different molecular components that play crucial roles and, moreover, that various chitin-binding proteins contain dissimilar chitin-binding domains across species that differ in affinity and specificity. Considering the various strategies from microbes and hosts focused on chitin recognition, it is evident that this carbohydrate plays a central role in plant–fungus interactions.
Combined biotic and abiotic stress resistance in tomato
Kissoudis, C. ; Chowdhury, R. ; Heusden, A.W. van; Wiel, C.C.M. van de; Finkers, H.J. ; Visser, R.G.F. ; Bai, Y. ; Linden, C.G. van der - \ 2015
Euphytica 202 (2015)2. - ISSN 0014-2336 - p. 317 - 332.
salt tolerance - oidium-neolycopersici - salinity tolerance - botrytis-cinerea - powdery mildew - abscisic-acid - plant-disease - phenotypic plasticity - solanum-lycopersicon - climate-change
Abiotic and biotic stress factors are the major constrains for the realization of crop yield potential. As climate change progresses, the spread and intensity of abiotic as well as biotic stressors is expected to increase, with increased probability of crops being exposed to both types of stress. Shielding crops from combinatorial stress requires a better understanding of the plant’s response and its genetic architecture. In this study, we evaluated resistance to salt stress, powdery mildew and to both stresses combined in tomato, using the Solanum habrochaites LYC4 introgression line (IL) population. The IL population segregated for both salt stress tolerance and powdery mildew resistance. Using SNP array marker data, QTLs were identified for salt tolerance as well as Na+ and Cl- accumulation. Salt stress increased the susceptibility of the population to powdery mildew in an additive manner. Phenotypic variation for disease resistance was reduced under combined stress as indicated by the coefficient of variation. No correlation was found between disease resistance and Na+ and Cl- accumulation under combined stress Most genetic loci were specific for either salt stress tolerance or powdery mildew resistance. These findings increase our understanding of the genetic regulation of responses to abiotic and biotic stress combinations and can provide leads to more efficiently breeding tomatoes and other crops with a high level of disease resistance while maintaining their performance in combination with abiotic stress.
Sensitivities of baseline isolates and boscalid-resistant mutants of Alternaria alternata from pistachio to fluopyram, penthiopyrad, and fluxapyroxad
Avenot, H.F. ; Biggelaar, H. van den; Morgan, D.P. ; Moral, J. ; Joosten, M.H.A.J. ; Michailides, T.J. - \ 2014
Plant Disease 98 (2014)2. - ISSN 0191-2917 - p. 197 - 205.
molecular characterization - botrytis-cinerea - inhibiting fungicides - california pistachio - didymella-bryoniae - sdhi fungicides - late blight - mutations - azoxystrobin - populations
Resistance of Alternaria alternata to boscalid, the first succinate dehydrogenase inhibitor (SDHI) fungicide labeled on pistachio, has become a common occurrence in California pistachio orchards and affects the performance of this fungicide. In this study, we established the baseline sensitivities of A. alternata to the new SDHIs fluopyram, fluxapyroxad, and penthiopyrad and assessed their cross resistance patterns with boscalid. Examination of the effective fungicide concentration that inhibits mycelial growth to 50% relative to the control (EC50) for 50 baseline isolates revealed that the majority were sensitive to boscalid, penthiopyrad, fluopyram, and fluxapyroxad. Analysis of EC50 values for boscalid for 117 A. alternata isolates originating from boscalid-exposed orchards showed that 44, 3, 1, and 69 isolates had sensitive, reduced sensitivity, moderately resistant, and highly resistant boscalid phenotypes, respectively. Molecular investigation of the occurrence of known SDH mutations showed that, among the 69 isolates highly resistant to boscalid, 44, 2, 14, and 1 isolates possessed the mutations leading to the H277Y, H277R, H134R, and H133R amino acid substitutions in AaSDHB, AaSDHB, AaSDHC, and AaSDHD subunits, respectively. Some SDHB or SDHC mutants displayed highly sensitive, sensitive, or reduced sensitivity phenotypes toward penthiopyrad or fluxapyroxad, whereas other had low, moderate, or high levels of resistance to these fungicides. In contrast, all the SDHB mutants were sensitive to fluopyram, while 10, 5, and 1 SDHC mutants had sensitive, reduced sensitivity, and moderately resistant fluopyram phenotypes, respectively. The SDHD mutant had reduced sensitivity to fluopyram and penthiopyrad but was highly resistant to fluxapyroxad. The discrepancies of cross-resistance patterns between SDHIs suggest that their binding sites in complex II may differ slightly and that additional mechanisms of resistance to these compounds are likely involved. Ultimately, the findings of this study should lead to the rational and sustained deployment of new SDHIs in Alternaria late blight spray programs.
Disease resistance or growth: the role of plant hormones in balancing immune responses and fitness costs
Denance, N. ; Sanchez Vallet, A. ; Goffner, D. ; Molina, A. - \ 2013
Frontiers in Plant Science 4 (2013). - ISSN 1664-462X
systemic acquired-resistance - pattern-recognition receptors - mediated defense responses - syringae pv. tomato - abscisic-acid - pseudomonas-syringae - salicylic-acid - arabidopsis-thaliana - botrytis-cinerea - ustilago-maydis
Plant growth and response to environmental cues are largely governed by phytohormones. The plant hormones ethylene, jasmonic acid, and salicylic acid (SA) play a central role in the regulation of plant immune responses. In addition, other plant hormones, such as auxins, abscisic acid (ABA), cytokinins, gibberellins, and brassinosteroids, that have been thoroughly described to regulate plant development and growth, have recently emerged as key regulators of plant immunity. Plant hormones interact in complex networks to balance the response to developmental and environmental cues and thus limiting defense-associated fitness costs. The molecular mechanisms that govern these hormonal networks are largely unknown. Moreover, hormone signaling pathways are targeted by pathogens to disturb and evade plant defense responses. In this review, we address novel insights on the regulatory roles of the ABA, SA, and auxin in plant resistance to pathogens and we describe the complex interactions among their signal transduction pathways. The strategies developed by pathogens to evade hormone-mediated defensive responses are also described. Based on these data we discuss how hormone signaling could be manipulated to improve the resistance of crops to pathogens.
Phyllosticta species on citrus: Risk estimation of resistance to QoI fungicides and identification of species with cytochrome b gene sequences
Stammler, G. ; Schutte, G.C. ; Speakman, J. ; Miessner, S. ; Crous, P.W. - \ 2013
Crop Protection 48 (2013). - ISSN 0261-2194 - p. 6 - 12.
guignardia-citricarpa - black spot - botrytis-cinerea - south-africa - mitochondrial-dna - pyrenophora-teres - valencia oranges - f129l mutation - causal agent - mangiferae
Isolates of three fungal species associated with citrus, Phyllosticta citricarpa, Phyllosticta citriasiana and Phyllosticta capitalensis, collected from different citrus growing countries of the world, were investigated for their sensitivities to the QoI fungicides pyraclostrobin and azoxystrobin. Isolates were highly sensitive in microtiter tests and EC50 values were in narrow ranges, which indicate no acquired adaptation to QoIs. The resistance risk of P. citricarpa to QoIs is considered low since an intron was found immediately after codon 143 in the cytochrome b gene. The presence of an intron is known to reduce the risk of the G143A mutation, the mutation which causes QoI resistance with high resistance factors. The other two species had no intron and therefore are considered having a higher resistance risk. Impact of these two species is rather low, since P. citriasiana is restricted in its regional and host distribution and P. capitalensis is non-pathogenic. Furthermore, the development of a rapid and reliable assay for species detection and identification was made possible based on an analysis of the cytochrome b gene.
Friend or foe: genetic and functional characterization of plant endophytic Pseudomonas aeruginosa
Kumar, A. ; Munder, A. ; Aravind, R. ; Eapen, S.J. ; Tümmler, B. ; Raaijmakers, J.M. - \ 2013
Environmental Microbiology 15 (2013)3. - ISSN 1462-2912 - p. 764 - 779.
iii secretion system - fluorescent pseudomonas - population-structure - opportunistic pathogen - biological-control - swarming motility - botrytis-cinerea - salicylic-acid - lung infection - diversity
Endophytic Pseudomonas aeruginosa strain BP35 was originally isolated from black pepper grown in the rain forest in Kerala, India. Strain PaBP35 was shown to provide significant protection to black pepper against infections by Phytophthora capsici and Radopholus similis. For registration and implementation in disease management programmes, several traits of PaBP35 were investigated including its endophytic behaviour, biocontrol activity, phylogeny and toxicity to mammals. The results showed that PaBP35 efficiently colonized black pepper shoots and displayed a typical spatiotemporal pattern in its endophytic movement with concomitant suppression of Phytophthora rot. Confocal laser scanning microscopy revealed high populations of PaBP35::gfp2 inside tomato plantlets, supporting its endophytic behaviour in other plant species. Polyphasic approaches to genotype PaBP35, including BOX-PCR, recN sequence analysis, multilocus sequence typing and comparative genome hybridization analysis, revealed its uniqueness among P.¿aeruginosa strains representing clinical habitats. However, like other P.¿aeruginosa strains, PaBP35 exhibited resistance to antibiotics, grew at 25–41°C and produced rhamnolipids and phenazines. PaBP35 displayed strong type II secretion effectors-mediated cytotoxicity on mammalian A549 cells. Coupled with pathogenicity in a murine airway infection model, we conclude that this plant endophytic strain is as virulent as clinical P.¿aeruginosa strains. Safety issues related to the selection of plant endophytic bacteria for crop protection are discussed.
Post-harvest Proteomics and Food Security
Pedreschi Plasencia, R.P. ; Lurie, S. ; Hertog, W. ; Nicolai, B. ; Mes, J.J. ; Woltering, E.J. - \ 2013
Proteomics 13 (2013)12-13. - ISSN 1615-9853 - p. 1772 - 1783.
cell-wall proteome - peach fruit - chilling injury - botrytis-cinerea - tomato fruit - citrus-fruit - sugar-beet - wide characterization - gel-electrophoresis - seed-germination
To guarantee sufficient food supply for a growing world population, efforts towards improving crop yield and plant resistance should be complemented with efforts to reduce postharvest losses. Post-harvest losses are substantial and occur at different stages of the food chain in developed and developing countries. In recent years a substantially increasing interest can be seen in the application of proteomics to understand post-harvest events. In the near future post-harvest proteomics will be poised to move from fundamental research to aiding the reduction of food losses. Proteomics research can help in reducing food losses through (i) identification and validation of gene products associated to specific quality traits supporting marker-assisted crop improvement programs, (ii) delivering markers of initial quality that allow optimization of distribution conditions and prediction of remaining shelf life for decision support systems and (iii) delivering early detection tools of physiological or pathogen related post-harvest problems. In this manuscript, recent proteomics studies on post-harvest and stress physiology are reviewed and discussed. Perspectives on future directions of post-harvest proteomics studies aiming to reduce food losses are presented.
Biocontrol and population dynamics of Fusarium spp. on wheat stubble in Argentina
Palazzini, J.M. ; Groenenboom-de Haas, B.H. de; Torres, A.M. ; Köhl, J. ; Chulze, S.N. - \ 2013
Plant Pathology 62 (2013)4. - ISSN 0032-0862 - p. 859 - 866.
head blight - clonostachys-rosea - botrytis-cinerea - biological-control - gibberella-zeae - quantitative detection - gliocladium-roseum - fumonisin content - crop residues - grain
The biocontrol effect of Clonostachys rosea (strains 016 and 1457) on Fusarium graminearum, F. avenaceum, F. verticillioides, F. langsethiae, F. poae, F. sporotrichioides, F. culmorum and Microdochium nivale was evaluated on naturally infected wheat stalks exposed to field conditions for 180 days. Experiments were conducted at two locations in Argentina, Marcos Juarez and Río Cuarto. Antagonists were applied as conidial suspensions at two inoculum levels. Pathogens were quantified by TaqMan real-time qPCR. During the first year at Marcos Juarez, biocontrol was observed in one antagonist treatment for F. graminearum after 90 days (73% reduction) but after 180 days, the pathogen decreased to undetectable levels. During the second year, biocontrol was observed in three antagonist treatments for F. graminearum and F. avenaceum (68·3% and 98·9% DNA reduction, respectively, after 90 days). Fusarium verticillioides was not controlled at Marcos Juarez. At Río Cuarto, biocontrol effects were observed in several treatments at different intervals, with a mean DNA reduction of 88·7% for F. graminearum and F. avenaceum, and 100% reduction for F. verticillioides in two treatments after 180 days. Populations of F. avenaceum and F. verticillioides were stable; meanwhile, F. graminearum population levels varied during the first 90 days, and low levels were observed after 180 days. The other pathogens were not detected. The study showed that wheat stalks were important reservoirs for F. avenaceum and F. verticillioides populations but less favourable for F. graminearum survival. Clonostachys rosea (strain 1457) showed potential to reduce the Fusarium spp. on wheat stalks
Source of vase life variation in cut roses: A review
Fanourakis, D. ; Pieruschka, R. ; Savvides, A. ; Macnish, A.J. ; Sarlikioti, V. ; Woltering, E.J. - \ 2013
Postharvest Biology and Technology 78 (2013). - ISSN 0925-5214 - p. 1 - 15.
relative air humidity - acoustic-emission profiles - plant-population density - miniature potted roses - hybrida l. plants - botrytis-cinerea - water relations - keeping quality - postharvest performance - vascular occlusion
In determining vase life (VL), it is often not considered that the measured VL in a particular experiment may greatly depend on both the preharvest and evaluation environmental conditions. This makes the comparison between studies difficult and may lead to erroneous interpretation of results. In this review, we critically discuss the effect of the growth environment on the VL of cut roses. This effect is mainly related to changes in stomatal responsiveness, regulating water loss, whereas cut flower carbohydrate status appears less critical. When comparing cultivars, postharvest water loss and VL often show no correlation, indicating that components such as variation in the tissue resistance to cavitate and/or collapse at low water potential play an important role in the incidence of water stress symptoms. The effect of the growth environment on these components remains unknown. Botrytis cinerea sporulation and infection, as well as cut rose susceptibility to the pathogen are also affected by the growth environment, with the latter being largely unexplored. A huge variability in the choices made with respect to the experimental setup (harvest/conditioning methods, test room conditions and VL terminating symptoms) is reported. We highlight that these decisions, though frequently overlooked, influence the outcome of the study. Specifications for each of these factors are proposed as necessary to achieve a common VL protocol. Documentation of both preharvest conditions and a number of postharvest factors, including the test room conditions, is recommended not only for assisting comparisons between studies, but also to identify factors with major effects on VL.
Emission index for evaluation of volatile organic compounds emitted from tomato plants in greenhouses
Takayama, K. ; Jansen, R.M.C. ; Henten, E.J. van; Verstappen, F.W.A. ; Bouwmeester, H.J. ; Nishina, H. - \ 2012
Biosystems Engineering 113 (2012)2. - ISSN 1537-5110 - p. 220 - 228.
mass-spectrometry - botrytis-cinerea - stress - system - health - design - light - scale
Measurement of volatile organic compounds (VOCs) emitted by plants allows us to monitor plant health status without touching the plant. To bring this technique a step further towards a practical plant diagnosis technique for greenhouse crop production, we have defined a numerical index named "Emission index" to evaluate VOC emissions from tomato plants isolated from ambient greenhouse air using an open-bottom chamber. The emission index of a VOC is a ratio of the concentration of the VOC in the air inside the chamber to that in the ambient greenhouse air and the index should be larger than one if the VOC is emitted by the plants in the chamber. Measurement of the emission indices of representative tomato VOCs proved that non-stressed tomato plants in a greenhouse emit n-hexanal, 2-carene, beta-phellandrene, alpha-copaene, beta-caryophyllene and (3E,7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT), do not emit (Z)-3-hexenol, and might absorb and/or adsorb n-hexanol. Another experiment proved that a routine crop maintenance operation, i.e. removal of old leaves from the lower part of plants and removal of side shoots, enhances the emissions of n-hexanal, (E)-2-hexenal, (Z)-3-hexenol, but does not enhance the emissions of alpha-copaene, methyl salicylate (MeSA) and TMTT. The results suggest that the measurement of emission index with the open-bottom chamber is a useful technique for monitoring VOC emissions by plants in a greenhouse under practical conditions. (C) 2012 IAgrE. Published by Elsevier Ltd. All rights reserved.
The FRP1 F-box gene has different functions in sexuality, pathogenicity and metabolism in three fungal pathogens
Jonkers, W. ; Kan, J.A.L. van; Tijm, P. ; Lee, Y.W. ; Tudzynski, P. ; Rep, M. ; Michielse, C.B. - \ 2011
Molecular Plant Pathology 12 (2011)6. - ISSN 1464-6722 - p. 548 - 563.
vascular wilt fungus - fusarium-oxysporum - botrytis-cinerea - gibberella-zeae - map kinase - reduced pathogenicity - filamentous fungi - protein-kinase - g-alpha - virulence
Plant-pathogenic fungi employ a variety of infection strategies; as a result, fungi probably rely on different sets of proteins for successful infection. The F-box protein Frp1, only present in filamentous fungi belonging to the Sordariomycetes, Leotiomycetes and Dothideomycetes, is required for nonsugar carbon catabolism and pathogenicity in the root-infecting fungus Fusarium oxysporum. To assess the role of Frp1 in other plant-pathogenic fungi, FRP1 deletion mutants were generated in Fusarium graminearum and Botrytis cinerea, and their phenotypes were analysed. Deletion of FgFRP1 in F. graminearum led to impaired infection of barley roots, but not of aerial plant parts. Deletion of BcFRP1 in B. cinerea did not show any effect on pathogenicity. Sexual reproduction, however, was impaired in both F. graminearum and B. cinerea FRP1 deletion mutants. The mutants of all three fungi displayed different phenotypes when grown on an array of carbon sources. The F. oxysporum and B. cinerea deletion mutants showed opposite growth phenotypes on sugar and nonsugar carbon sources. Replacement of FoFRP1 in F. oxysporum with the B. cinerea BcFRP1 resulted in the restoration of pathogenicity, but also in a switch from impaired growth on nonsugar carbon sources to impaired growth on sugar carbon sources. This effect could be ascribed in part to the B. cinerea BcFRP1 promoter sequence. In conclusion, the function of the F-box protein Frp1, despite its high sequence conservation, is not conserved between different fungi, leading to differential requirements for pathogenicity and carbon source utilization.
Detection of diseased plants by analysis of volatile organic compound emission
Jansen, R.M.C. ; Wildt, J. ; Kappers, I.F. ; Bouwmeester, H.J. ; Hofstee, J.W. ; Henten, E. van - \ 2011
Annual Review of Phytopathology 49 (2011). - ISSN 0066-4286 - p. 157 - 174.
chromatography-mass-spectrometry - precision agriculture - methyl salicylate - tomato plants - biosensor technology - rapid-determination - thermal-desorption - gas-chromatograph - emitted volatiles - botrytis-cinerea
This review focuses on the detection of diseased plants by analysis of volatile organic compound (VOC) emissions. It includes an overview of studies that report on the impact of infectious and noninfectious diseases on these emissions and discusses the specificity of disease-induced emissions. The review also provides an overview of processes that affect the gas balance of plant volatiles, including their loss processes. These processes are considered as important because they contribute to the time-dynamic concentration profiles of plant-emitted volatiles. In addition, we describe the most popular techniques currently in use to measure volatiles emitted from plants, with emphasis on agricultural application. Dynamic sampling coupled with gas chromatography and followed by an appropriate detector is considered as the most appropriate method for application in agriculture. It is recommended to evaluate the state-of-the-art in the fields concerned with this method and to explore the development of a new instrument based on the specific needs for application in agricultural practice. However, to apply such an instrument in agriculture remains a challenge, mainly due to high costs
Stepwise screening of microorganisms for commercial use in biological control of plant pathogenic fungi and bacteria. Biological Control
Köhl, J. ; Postma, J. ; Nicot, P. ; Ruocco, M. - \ 2011
Biological Control 57 (2011)1. - ISSN 1049-9644 - p. 1 - 12.
biocontrol agents - coniothyrium-minitans - botrytis-cinerea - new-zealand - selection - antagonists - soil - rhizosphere - suppression - diseases
The development of new biocontrol products against plant diseases requires screening of high numbers of candidate antagonists. Antagonists for commercial use have to fulfill many different requirements. Besides being active against the specific targeted plant pathogens they must be safe and cost-effective. Important criteria besides pathogenic efficacy are market size, ecological characteristics, production costs, safety, environmental risks, and possibilities for intellectual property protection. A stepwise screening program considering these very different aspects is proposed. Research highlights ¿ Stepwise screening of microorganisms for commercial use in biocontrol. ¿ Multi-disciplinary approach considering many aspects besides control efficacy. ¿ Examples for protocols for use in screening programmes illustrating this approach. Article Outline 1. Introduction 2. Screening steps 2.1. Step 1: Assessment of targeted crop, disease and markets 2.2. Step 2: Origin and isolation of candidate antagonists 2.3. Step 3: Preliminary assessments in rapid-throughput screening systems 2.4. Step 4: Identification of candidate antagonists and database mining 2.5. Step 5: Efficacy testing against pathogens on plants 2.6. Step 6: Preliminary tests on mass production 2.7. Step 7: Development and testing of a pilot formulation and estimation of registration costs 2.8. Step 8: Field testing and upscaling mass production 2.9. Step 9: Integration into cropping systems Discussion
Volatile organic compounds as a diagnostic marker of late blight infected potato plants: A pilot study
Laothawornkitkul, J. ; Jansen, R.M.C. ; Smid, H.M. ; Bouwmeester, H.J. ; Muller, J. ; Bruggen, A.H.C. van - \ 2010
Crop Protection 29 (2010)8. - ISSN 0261-2194 - p. 872 - 878.
phytophthora-infestans - botrytis-cinerea - damaged plants - in-vitro - tomato - leaves - lipoxygenase - emissions - variability - biosensor
Volatiles from potato plants infected with Phytophthora infestans (Mont.) de Bary were monitored by in situ headspace sampling. The sampling was done in four periods i.e. 28–42, 52–66, 76–90, and 100–114 h after inoculation (HAI). The headspace samples were analyzed by a gas chromatography–flame ionization detector (GC–FID) to assess the differences in volatile fingerprints between the infected-plant group and control groups, i.e. non-inoculated-plant and empty-vessel groups. The samples were subsequently analyzed by gas chromatography–mass spectrometry to identify specific peaks observed by GC–FID. Spore germination, infection, symptom development and sporulation were also monitored to ascertain the disease developmental stage when marker volatiles were first generated. The first symptoms of infection were visible after two days. Three marker volatiles i.e. (E)-2-hexenal, 5-ethyl-2(5H)-furanone and benzene-ethanol were found in the third and fourth trapping periods (3–4 days after inoculation) when sporangiophores were already formed. The volatile metabolites from blighted plants could be applied for sensor development to detect the occurrence of the disease in the field as well as for investigation of volatile production in relation to plant responses to infection.
Screening of biocontrol agents for control of foliar diseases
Köhl, J. - \ 2009
In: Recent Developments in Management of Plant Diseases / Gisi, U., Chet, I., Gullino, M.L., Dordrecht Heidelberg London New York : Springer (Plant Pathology in the 21st Century, Vol. 1. Vol. 1, part 2) - ISBN 9781402088032 - p. 107 - 119.
apple scab pathogen - venturia-inaequalis - biological-control - botrytis-cinerea - trichoderma-harzianum - ulocladium-atrum - solar-radiation - powdery mildew - aphid honeydew - phyllosphere
Candidate antagonists for the development of biocontrol agents have to fulfill many criteria. The criterion often investigated first in detail is the antagonistic potential of candidates against the target pathogen. However, candidates must also have high ecological competence, must be suitable for an economically feasible production and must be safe in use. Consequently, a broad range of criteria must be tested to fulfill the key factors for success of a biocontrol product. Assays are needed to test such major criteria in simple and inexpensive high throughput systems to exclude candidates in an early stage which may show strong antagonisms but do not fulfill other major criteria for a successful commercialization. The case of a screening program aimed at the biological control of apple scab caused by Venturia inaequalis is presented and discussed. Keywords Biological control - Foliar diseases - Screening - Selection criteria
A Phytophthora sojae G protein alpha subunit is involved in chemotaxis to soybean isoflavones
Hua, C. ; Wang, Y. ; Zheng, X. ; Dou, D. ; Zhang, Z. ; Govers, F. - \ 2008
Eukaryotic Cell 7 (2008)12. - ISSN 1535-9778 - p. 2133 - 2140.
transcription factor - zoospore encystment - hyphal growth - saccharomyces-cerevisiae - signal-transduction - cyst germination - botrytis-cinerea - beta-subunit - infestans - oomycete
For the soybean pathogen Phytophthora sojae, chemotaxis of zoospores to isoflavones is believed to be critical for recognition of the host and for initiating infection. However, the molecular mechanisms underlying this chemotaxis are largely unknown. To investigate the role of G-protein and calcium signaling in chemotaxis, we analyzed the expression of several genes known to be involved in these pathways and selected one that was specifically expressed in sporangia and zoospores but not in mycelium. This gene, named PsGPA1, is a single-copy gene in P. sojae and encodes a G-protein subunit that shares 96% identity in amino acid sequence with that of Phytophthora infestans. To elucidate the function, expression of PsGPA1 was silenced by introducing antisense constructs into P. sojae. PsGPA1 silencing did not disturb hyphal growth or sporulation but severely affected zoospore behavior, including chemotaxis to the soybean isoflavone daidzein. Zoospore encystment and cyst germination were also altered, resulting in the inability of the PsGPA1-silenced mutants to infect soybean. In addition, the expressions of a calmodulin gene, PsCAM1, and two calcium- and calmodulin-dependent protein kinase genes, PsCMK3 and PsCMK4, were increased in the mutant zoospores, suggesting that PsGPA1 negatively regulates the calcium signaling pathways that are likely involved in zoospore chemotaxis
Large-scale gene discovery in the Septoria tritici blotch fungus Mycosphaerella graminicola with a focus on in planta expression
Kema, G.H.J. ; Lee, T.A.J. van der; Mendes, O. ; Verstappen, E.C.P. ; Klein Lankhorst, R.M. ; Sandbrink, H. ; Burgt, A. van der; Zwiers, L.H. ; Csukai, M. ; Waalwijk, C. - \ 2008
Molecular Plant-Microbe Interactions 21 (2008)9. - ISSN 0894-0282 - p. 1249 - 1260.
major facilitator superfamily - rice blast fungus - genome sequence - fusarium-graminearum - magnaporthe-grisea - stagonospora-nodorum - phytophthora-sojae - transporter genes - botrytis-cinerea - toxic compounds
The foliar disease septoria tritici blotch, caused by the fungus Mycosphaerella graminicola, is currently the most important wheat disease in Europe. Gene expression was examined under highly different conditions, using 10 expressed sequence tag libraries generated from M. graminicola isolate IPO323 using seven in vitro and three in planta growth conditions. To identify fungal clones in the interaction libraries, we developed a selection method based on hybridization with the entire genomic DNA of M. graminicola, to selectively enrich these libraries for fungal genes. Assembly of the 27,007 expressed sequence tags resulted in 9,190 unigenes, representing 5.2 Mb of the estimated 39-Mb genome size of M. graminicola. All libraries contributed significantly to the number of unigenes, especially the in planta libraries representing different stages of pathogenesis, which covered 15% of the library-specific unigenes. Even under presymptomatic conditions (5 days postinoculation), when fungal biomass is less than 5%, this method enabled us to efficiently capture fungal genes expressed during pathogenesis. Many of these genes were uniquely expressed in planta, indicating that in planta gene expression significantly differed from in vitro expression. Examples of gene discovery included a number of cell wall-degrading enzymes, a broad set of genes involved in signal transduction (n = 11) and a range of ATP-binding cassette (n = 20) and major facilitator superfamily transporter genes (n = 12) potentially involved in protection against antifungal compounds or the secretion of pathogenicity factors. In addition, evidence is provided for a mycovirus in M. graminicola that is highly expressed under various stress conditions, in particular, under nitrogen starvation. Our analyses provide a unique window on in vitro and in planta gene expression of M. graminicola.
Mapping and characterization of novel parthenocarpy QTLs in tomato
Gorguet, B.J.M. ; Eggink, P.M. ; Ocaña, J. ; Tiwari, A. ; Schipper, E.H. ; Finkers, H.J. ; Visser, R.G.F. ; Heusden, A.W. van - \ 2008
Theoretical and Applied Genetics 116 (2008)6. - ISSN 0040-5752 - p. 755 - 767.
quantitative trait loci - lycopersicon-esculentum - botrytis-cinerea - resistance - hirsutum - set - auxin-response-factor8 - identification - introgression - chromosomes
Parthenocarpy is the development of the fruit in absence of pollination and/or fertilization. In tomato, parthenocarpy is considered as an attractive trait to solve the problems of fruit setting under unfavorable conditions. We studied the genetics of parthenocarpy in two different lines, IL5-1 and IVT-line 1, both carrying Solanum habrochaites chromosome segments. Parthenocarpy in IL5-1 is under the control of two QTLs, one on chromosome 4 (pat4.1) and one on chromosome 5 (pat5.1). IVT-line 1 also contains two parthenocarpy QTLs, one on chromosome 4 (pat4.2) and one on chromosome 9 (pat9.1). In addition, we identified one stigma exsertion locus in IL5-1, located on the long arm of chromosome 5 (se5.1). It is likely that pat4.1, from IL5-1 and pat4.2, from IVT-line 1, both located near the centromere of chromosome 4 are allelic. By making use of the microsynteny between tomato and Arabidopsis in this genetic region, we identified ARF8 as a potential candidate gene for these two QTLs. ARF8 is known to act as an inhibitor for further carpel development in Arabidopsis, in absence of pollination/fertilization. Expression of an aberrant form of the Arabidopsis ARF8 gene, in tomato, has been found to cause parthenocarpy. This candidate gene approach may lead to the first isolation of a parthenocarpy gene in tomato and will allow further use in several crop species
Scanning electron microscopy of the interaction between Cryptococcus magnus and Colletotrichum gloeosporioides on papaya fruit = Microscopia eletrônica de varredura da interação entre Cryptococcus magnus e Colletotrichum gloeosporioides em frutos de mamão
Capdeville, G. ; Souza, M.T. ; Santos, J.R.P. ; Miranda, S.P. ; Caetano, A.R. ; Falcao, R. ; Gomes, A.C.M.M. - \ 2007
Pesquisa Agropecuaria Brasileira 42 (2007)11. - ISSN 0100-204X - p. 1537 - 1544.
blue mold - postharvest biocontrol - botrytis-cinerea - apple fruit - yeasts - mode - pathogens - rot
The objective of this work was to investigate possible modes of action of the yeast Cryptococcus magnus in controlling anthracnose (Colletotrichum gloeosporioides) on post harvested papaya fruits. Scanning electron microscopy was used to analyze the effect of the yeast on inoculations done after harvest. Results showed that C. magnus is able to colonize wound surfaces much faster than the pathogen, outcompeting the later for space and probably for nutrients. In addition, C. magnus produces a flocculent matrix, which affects hyphae integrity. The competition for space and the production of substances that affect hyphae integrity are among the most important modes of action of this yeast
Control of Mycosphaerella graminicola on wheat seedlings by medical drugs known to modulate the activity of ATP-binding cassette transporters
Roohparvar, R. ; Huser, A. ; Zwiers, L.H. ; Waard, M.A. de - \ 2007
Applied and Environmental Microbiology 73 (2007)15. - ISSN 0099-2240 - p. 5011 - 5019.
major facilitator superfamily - natural toxic compounds - multidrug-resistance - abc transporters - botrytis-cinerea - efflux pump - fungicide sensitivity - virulence - plant - reversal
Medical drugs known to modulate the activity of human ATP-binding cassette (ABC) transporter proteins (modulators) were tested for the ability to potentiate the activity of the azole fungicide cyproconazole against in vitro growth of Mycosphaerella graminicola and to control disease development due to this pathogen on wheat seedlings. In vitro modulation of cyproconazole activity could be demonstrated in paper disk bioassays. Some of the active modulators (amitriptyline, flavanone, and phenothiazines) increased the accumulation of cyproconazole in M. graminicola, suggesting that they reversed cyproconazole efflux. However, synergism between cyproconazole and modulators against M. graminicola on wheat seedlings could not be shown. Despite their low in vitro toxicity to M. graminicola, some modulators (amitriptyline, loperamide, and promazine) did show significant intrinsic disease control activity in preventive and curative foliar spray tests with wheat seedlings. The results suggest that these compounds have indirect disease control activity based on modulation of fungal ABC transporters essential for virulence and constitute a new class of disease control agents.