PCFruit Research Station

Belgium

PCFruit Research Station

Belgium

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Verjans W.,Pcfruit Research Station | Remy S.,Pcfruit Research Station | Rosa N.,University of Lisbon | Schoofs H.,Pcfruit Research Station | Deckers T.,Pcfruit Research Station
Acta Horticulturae | Year: 2016

The natural crop load varies highly from year to year in 'Golden Delicious' apple under Belgian climatological conditions. To study this variation in crop load, the number of fruits tree-1 year-1 was correlated with several parameters in two different orchards for the period 2007 until 2014. Only the data of the untreated trial were used to exclude the effect of hand thinning or of plant growth regulators. Pearson correlation coefficients revealed that there are very strong negative correlations between the number of fruits tree-1 and the day number of different phenological stages at flowering time. Besides the day number at which the phenological stages occur, also the length of the period between two phenological stages had a strong correlation with the number of fruits tree-1. In the case of the period between the end of flowering and the beginning of June drop the correlation was strong and positive with the number of fruits tree-1. A comparable strong correlation was obtained between the length of the period between leaf fall in the previous year and the bud break occurrence. A moderate negative correlation occurred between the number of fruits tree-1 and the yield of the previous year. Finally, the number of fruits tree-1 strongly correlated with low flower clusters situation (less than 150 tree-1), while, when the flower cluster load was high (more than 300 tree-1), no correlation was found. © 2016, International Society for Horticultural Science. All rights reserved.


Holtappels M.,Hasselt University | Vrancken K.,PCFruit Research Station | Noben J.P.,transnational University of Limburg | Remans T.,Hasselt University | And 3 more authors.
Journal of Proteomics | Year: 2016

Erwinia amylovora is a Gram-negative plant pathogen that causes fire blight. This disease affects most members of the Rosaceae family including apple and pear. Here, an infection model is introduced to study proteomic changes in a highly virulent E. amylovora strain upon interaction with its host as compared to a lower virulent strain. For this purpose separate shoots of apple rootstocks were wound-infected and when infection became systemic, bacterial cells were isolated and processed for analysis in a proteomics platform combining 2-D fluorescence difference gel electrophoresis and mass spectrometry. Comparing the proteome of the isolates, significant abundance changes were observed in proteins involved in sorbitol metabolism, amylovoran production as well as in protection against plant defense mechanisms. Furthermore several proteins associated with virulence were more abundant in the higher virulent strain. Changes at the proteome level showed good accordance at the transcript level, as was verified by RT-qPCR. In conclusion, this infection model may be a valuable tool to unravel the complexity of plant-pathogen interactions and to gain insight in the molecular mechanisms associated with virulence of E. amylovora, paving the way for the development of plant-protective interventions against this detrimental disease. Significance: During this research a first time investigation was performed on the proteome of E. amylovora, grown inside a susceptible host plant. This bacterium is the causal agent of fire blight, which can affect most members of the Rosaceae family including apple and pear. To do so, an artificial infection model on shoots of apple rootstocks was optimized and employed. When infection was systemic, bacterial cells were extracted from the plant tissue followed by extraction of the proteins from the bacteria. Further processing of the proteins was done by using a 2-D fluorescence difference gel electrophoresis analysis followed by mass spectrometry. By the use of two strains differing in their virulent ability, we were able to draw conclusions concerning virulence and behavior of different strains inside the host. This research provides a model to investigate plant-pathogen interactions and more importantly, we identified possible new targets for the development of novel control methods against this devastating disease. © 2016 Elsevier B.V.


Holtappels M.,Hasselt University | Vrancken K.,PCFruit Research Station | Schoofs H.,PCFruit Research Station | Deckers T.,PCFruit Research Station | And 3 more authors.
Journal of Proteomics | Year: 2015

Erwinia amylovora is a Gram-negative bacterium that causes the destructive disease fire blight affecting most members of the Rosaceae family, of which apple and pear are economically the most important hosts. E. amylovora has been considered as a homogeneous species in whole, although significant differences in virulence patterns have been observed. However, the underlying causes of the differences in virulence remain to be discovered. In a first-time comparative proteomic approach using E. amylovora, 2D differential in-gel electrophoresis (DIGE) was used to identify proteins that could explain the gradual difference in virulence between four different strains. Two important proteins were identified, FliC and CheY, both involved in flagella structure, motility and chemotaxis, which were more abundant in the least virulent strain. In the highly virulent strains the protein GalF, involved in amylovoran production, was more abundant, which was consistent with the higher expression of the gene and the higher amylovoran content in this strain in vitro. Together, these results confirm the involvement of amylovoran in virulence, but also imply an indirect role of flagellin in virulence as elicitor of plant defence. Biological significance: This research provides new insights into our current understanding of the virulence of Erwinia amylovora. This plant-pathogen is considered a homogeneous species although different strains show differences in virulence. Despite the efforts made on the genomic level which resulted in the discovery of virulence factors, the reason for the different virulence patterns between strains has not yet been identified. In our lab we used a comparative proteomic approach, which has never been published before, to identify proteins involved in these differences between strains and hereby possibly involved in virulence. Our results provide interesting insights in virulence and present us with the opportunity to glance into the proteome of E. amylovora. © 2015.


PubMed | transnational University of Limburg, PCFruit Research Station and Hasselt University
Type: | Journal: Journal of proteomics | Year: 2016

Erwinia amylovora is a Gram-negative plant pathogen that causes fire blight. This disease affects most members of the Rosaceae family including apple and pear. Here, an infection model is introduced to study proteomic changes in a highly virulent E. amylovora strain upon interaction with its host as compared to a lower virulent strain. For this purpose separate shoots of apple rootstocks were wound-infected and when infection became systemic, bacterial cells were isolated and processed for analysis in a proteomics platform combining 2-D fluorescence difference gel electrophoresis and mass spectrometry. Comparing the proteome of the isolates, significant abundance changes were observed in proteins involved in sorbitol metabolism, amylovoran production as well as in protection against plant defense mechanisms. Furthermore several proteins associated with virulence were more abundant in the higher virulent strain. Changes at the proteome level showed good accordance at the transcript level, as was verified by RT-qPCR. In conclusion, this infection model may be a valuable tool to unravel the complexity of plant-pathogen interactions and to gain insight in the molecular mechanisms associated with virulence of E. amylovora, paving the way for the development of plant-protective interventions against this detrimental disease.During this research a first time investigation was performed on the proteome of E. amylovora, grown inside a susceptible host plant. This bacterium is the causal agent of fire blight, which can affect most members of the Rosaceae family including apple and pear. To do so, an artificial infection model on shoots of apple rootstocks was optimized and employed. When infection was systemic, bacterial cells were extracted from the plant tissue followed by extraction of the proteins from the bacteria. Further processing of the proteins was done by using a 2-D fluorescence difference gel electrophoresis analysis followed by mass spectrometry. By the use of two strains differing in their virulent ability, we were able to draw conclusions concerning virulence and behavior of different strains inside the host. This research provides a model to investigate plant-pathogen interactions and more importantly, we identified possible new targets for the development of novel control methods against this devastating disease.


PubMed | transnational University of Limburg, PCFruit Research Station and Hasselt University
Type: | Journal: Journal of proteomics | Year: 2015

Erwinia amylovora is a Gram-negative bacterium that causes the destructive disease fire blight affecting most members of the Rosaceae family, of which apple and pear are economically the most important hosts. E. amylovora has been considered as a homogeneous species in whole, although significant differences in virulence patterns have been observed. However, the underlying causes of the differences in virulence remain to be discovered. In a first-time comparative proteomic approach using E. amylovora, 2D differential in-gel electrophoresis (DIGE) was used to identify proteins that could explain the gradual difference in virulence between four different strains. Two important proteins were identified, FliC and CheY, both involved in flagella structure, motility and chemotaxis, which were more abundant in the least virulent strain. In the highly virulent strains the protein GalF, involved in amylovoran production, was more abundant, which was consistent with the higher expression of the gene and the higher amylovoran content in this strain in vitro. Together, these results confirm the involvement of amylovoran in virulence, but also imply an indirect role of flagellin in virulence as elicitor of plant defence.This research provides new insights into our current understanding of the virulence of Erwinia amylovora. This plant-pathogen is considered a homogeneous species although different strains show differences in virulence. Despite the efforts made on the genomic level which resulted in the discovery of virulence factors, the reason for the different virulence patterns between strains has not yet been identified. In our lab we used a comparative proteomic approach, which has never been published before, to identify proteins involved in these differences between strains and hereby possibly involved in virulence. Our results provide interesting insights in virulence and present us with the opportunity to glance into the proteome of E. amylovora.


Janssens P.,Soil Service of Belgium | Deckers T.,PCFruit Research Station | Elsen F.,Soil Service of Belgium | Elsen A.,Soil Service of Belgium | And 3 more authors.
Agricultural Water Management | Year: 2011

The present study examines the need for irrigation in pear trees (Pyrus Communis, cv. 'Conference') under low evaporative demand conditions, like in Belgium, in order to maintain a consistent fruit yield and high fruit size. To determine the sensitivity of the pear yield under low evaporative demand conditions three different orchards were monitored. The study shows that a Ψsoil of -60kPa during shoot growth has no effect on fruit yield but lower Ψsoil values induced a decline in both fruit size and total yield. Just as for arid environments a Ψstem of -1.5MPa is related to negative yield responses. In dry conditions lower Ψsoil and Ψstem values were observed in root pruned trees compared to not root pruned trees in the same irrigation treatment, however without yield decline. In one orchard a biannual bearing tendency was observed after root pruning. Furthermore intensive Ψsoil measurements show a high variation in Ψsoil between orchards, and within an orchard. This underlines the need for irrigation management on a parcel level and the need for new irrigation scheduling techniques which take the spatial variation in the orchard into account. © 2011 Elsevier B.V.


Schoofs H.,Pcfruit Research Station | Deckers T.,Pcfruit Research Station | Verjans W.,Pcfruit Research Station | Bylemans D.,Pcfruit Research Station
Acta Horticulturae | Year: 2014

Fire blight, caused by the bacteria Erwinia amylovora (Burill, Winslow et al.), is already more than 30 years present in Belgian fruit growing areas and still remains an important threat leading each year to economic losses in orchards as well as in fruit tree nurseries. Since 2005, the use of the antibiotic streptomycin is forbidden in Belgium and new strategies to control fire blight have been developed. Early season copper applications are considered to be important as they can drive bacteria in the Viable But Non Culturable (VBNC) state and contribute to reduce the inoculum in the orchards in the beginning of the season. During bloom, when the infection risk is high, it is possible to apply BlossomProtect, a compound based on the antagonist Aureobasidium pullulans. In the postfloral period, decreasing the susceptibility of the host plants towards fire blight infections using PDE molecules (Plant Defense Enhancing molecules) becomes the predominant strategy. Two PDE molecules Vacciplant (laminarin) and Aliette (fosetyl-Al) have been registered against fire blight. PDE molecules should be applied preventively, prior to the infection, so that the defense mechanisms of the plants can be switched on in time. Vacciplant (laminarin) is more considered for the protection of the blossoms while fosetyl-Al shows an effect against different types of infections on blossoms, shoots and fruits. A reduction in the disease progression and a clear reduction in the ooze formation on the infected shoots and fruits were observed on plants treated three times with fosetyl-Al and this is considered to be a very interesting factor in the fire blight epidemiology. An abiotic stress effect was observed with repeated heavy metal application like copper (Cu) and manganese (Mn) reducing fire blight susceptibility. Therefore, Mn applications during the growing season can be helpful for fire blight control and for fruit quality improvement. In contrast, during the same period, application of Cu is not recommended due to the cumulative phytotoxic effect. © 2014, International Society for Horticultural Science. All rights reserved.


Janssens P.,Soil Service of Belgium | Elsen F.,Soil Service of Belgium | Elsen A.,Soil Service of Belgium | Deckers T.,PCFruit Research Station | Vandendriessche H.,Catholic University of Leuven
Acta Horticulturae | Year: 2011

Pear growing (Pyrus Communis 'Conference') is an important part of horticulture in Belgium and The Netherlands. Drip irrigation techniques are implemented to achieve maximum production with a high fruit size distribution. The financial return of fruits having a diameter of ≥60 mm is twice the return of smaller sized fruits (≤55 mm). Maximum fruit size distribution and high productivity on 'Conference' pear trees can be achieved by applying regulated deficit irrigation (RDI). However, unpredictable summer rains and drought periods make it difficult to establish the optimal irrigation thresholds. To overcome these difficulties, an adapted Soil Water Balance model is presented to monitor the evolution of soil water content in the root zone on a daily basis. The input parameters for the model are soil water retention characteristics, rain, irrigation events and evapotranspiration. A specific algorithm has been developed for drip irrigation and tree transpiration in an orchard with weed free strips under the trees and grass strips between tree rows. Gravimetric moisture determination is used to calibrate the model during the growing season. The performance of the model was studied in three commercial orchards in the period 2008-2009. A significant correlation (R>0.80) was observed between predicted and observed soil water content. It illustrates the possibilities of the approach to use the soil water balance model as a base to schedule the irrigation for pear trees under orchard conditions with sufficient accuracy.


Deckers T.,PCFruit Research Station
Communications in agricultural and applied biological sciences | Year: 2010

Fire blight, caused by the bacterium Erwinia amylovora (Burill Winslow et al.), is a very important bacterial disease on apple and pear orchards with devastating effects in some production area and in some years. Fire blight control consists in a whole strategy of measures that should start with control measures in and around the fruit tree nurseries. Only the use of Vacciplant (Laminarin), an inducer of the self-defence mechanism, is registered in Belgium since 2009. In other European countries Fosethyl-Al has been registered for fire blight control. Recently, research trials have been done at Pcfruit research station for several years on the activity of ALiette (fosethyl-Al) against fire blight. Fosethyl-Al, also a plant defence enhancing molecule, applied preventively 3 times at a dose of 3.75 kg/ha standard orchard (3 x 3000 g a.i./ha standard orchard), showed a reduction in the host susceptibility and decreased the disease development on artificial inoculated flower clusters and shoots. Also a clear reduction in the ooze droplet formation on artificially inoculated immature fruitlets has been observed with this molecule. This reduction in the bacterial ooze formation is considered as a very important factor in the spread of the disease in the orchard.


van Beek J.,Catholic University of Leuven | Tits L.,Catholic University of Leuven | Somers B.,Catholic University of Leuven | Deckers T.,Pcfruit Research Station | And 2 more authors.
International Journal of Applied Earth Observation and Geoinformation | Year: 2015

Satellite remote sensing provides an alternative to time-consuming and labor intensive in situ measurements of biophysical variables in agricultural crops required for precision agriculture applications. In orchards, however, the spatial resolution causes mixtures of canopies and background (i.e. soil, grass and shadow), hampering the estimation of these biophysical variables. Furthermore, variable background mixtures obstruct meaningful comparisons between different orchard blocks, rows or within each row. Current correction methodologies use spectral differences between canopies and background, but struggle with a vegetated orchard floor. This background influence and the lack of a generic solution areaddressed in this study. Firstly, the problem was demonstrated in a controlled environment for vegetation indices sensitive to chlorophyll content, water content and leaf area index. Afterwards, traditional background correction methods (i.e. soil-adjusted vegetation indices and signal unmixing) were compared to the proposed vegetation index correction. This correction was based on the mixing degree of each pixel (i.e. tree cover fraction) to rescale the vegetation indices accordingly and was applied to synthetic and WorldView-2 satellite imagery. Through the correction, the effect of background admixture for vegetation indices was reduced, and the estimation of biophysical variables was improved (δR2= 0.2-0.31). © 2014 Elsevier B.V.

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