Samen op zoek naar oplossingen voor probleemplagen in de biologische teelt van houtig kleinfruit

Biologisch geteeld kleinfruit is enorm geliefd bij het grote publiek. Biotelers van houtig kleinfruit kampen echter met een aantal probleemplagen en -ziekten die ze zonder de krachtige chemische gewasbeschermingsmiddelen het hoofd moeten bieden. Daarom werd in 2013 in het kader van een CCBT-project in gezamenlijk overleg gezocht naar alternatieve oplossingen voor de bestrijding van deze plagen en ziekten. In de loop van dit project werden diverse overlegmomenten georganiseerd tussen telers, voorlichting en onderzoekers waarin de prioriteiten voor het onderzoek werden bepaald (dit uiteraard vooral door de biotelers zelf). Bedrijven waar proeven konden plaatsvinden werden in overleg met het Bio-bedrijfsnetwerk kleinfruit geselecteerd (het gaat dus om ‘on farm’ onderzoek bij biobedrijven) en afspraken werden gemaakt rond proefdesign, proefobjecten en taakverdeling. Hierbij werd rekening gehouden met de ervaringen van onderzoekers, de ervaringen van biofruittelers, en de eventueel aanwezige kennis en ervaringen in het buitenland. Concreet werden er in de loop van 2013 dan 5 proeven georganiseerd: - Feromoonverwarring voor bessenglasvlinder - Monitoring van Drosophila suzukii - Botrytis bestrijding bij bramen met het flying doctors systeem - Bestrijding van bramengalmijt met nuttigen - Witziektebestrijding bij herfstframboze

Probleemplagen in de bio pitfruitteelt: alternatieve bestrijdingsmiddelen

Het project “Praktijkgericht onderzoek en inzet van alternatieve bestrijdingsmiddelen voor de controle van probleemplagen in de biologische pitfruitteelt” had tot doel een bijdrage te leveren aan de teelt- en de bedrijfszekerheid van biologische pitfruitbedrijven. Spruzit (pyrethrinen met synergist piperonylbutoxide (PBO), dat gebruikt werd voor (correctie)behandelingen tegen probleemplagen in de biologische pitfruitteelt is niet meer in de handel sinds januari 2018. Aan de hand van de proeven die in dit project uitgevoerd werden, werd kennis opgedaan met nieuwe middelen tegen meer algemene plagen of met gekende middelen tegen nieuwe plagen. Mogelijk dankzij dit project kunnen een aantal middelen een uitbreiding van hun etiket krijgen. De kennis uit deze proeven voortgevloeid zal via Proefcentrum Fruitteelt continu ter beschikking gesteld worden van de fruittelers en zal als basis dienen voor verdere initiatieven in de zoektocht naar oplossingen voor probleem plagen in de biologische appel- en perenteelt

Marking Drosophila suzukii (Diptera : Drosophilidae) with fluorescent dusts

The marking of Drosophila suzukii can be an important instrument for studying the ecology and behaviour of this economically important fruit pest, aiding the development of new Integrated Pest Management (IPM) tools or strategies. There is, however, a need for a cost-effective methodology that provides an easily detectable and stable mark. Whereas fluorescent pigment powders are often used in entomological research, the pigments (series, dyes), application techniques, or doses need to be evaluated for each studied species in terms of their efficacy and possible adverse effects on the performance of the insect. The effectiveness of different application techniques and dyes (RadGlo® TP-series) and their effect on the survival of adult D. suzukii were investigated in the laboratory. Furthermore, the influence of the marking on the behaviour of the flies was examined in laboratory trap assays (olfaction) and a field recapture study (general orientation). The persistence and detectability of the marks was evaluated both on living flies (for different application techniques) and dead flies under trapping/storage conditions. The use of fluorescent powders to mark D. suzukii flies yielded a clearly detectable and highly persistent mark, without any adverse effects on the survival and behaviour of the flies

Olfactory preference of Drosophila suzukii shifts between fruit and fermentation cues over the season : effects of physiological status

Worldwide monitoring programs of the invasive fruit pest Drosophila suzukii Matsumura (Diptera: Drosophilidae), using fermentation baits like apple cider vinegar (ACV), revealed a counterintuitive period of low trap catches during summer, followed by an autumn peak. In this study, we demonstrate that ACV baited traps indeed provide a distorted image of the D. suzukii population dynamics as it is possible to capture higher numbers during this "low capture period" with synthetic lures. It was hypothesised that the preference of D. suzukii populations for fermentation cues like ACV is most pronounced during autumn, winter and spring, while the flies prefer fresh fruit cues during summer and that this seasonal preference is related to the changing physiology of the flies over the season. To test this hypothesis, the preference between fermentation cues (ACV) and host fruits (strawberries) and the effect of physiology (sex, seasonal morphology and feeding, mating and reproductive status) was investigated both in olfactometer laboratory experiments and a year-round field preference experiment. In olfactometer experiments we demonstrated that protein deprived females, virgin females with a full complement of unfertilised eggs and males show a strong preference for fermentation cues while fully fed reproductive summer morph females generally prefer fruit cues. These findings indicate that D. suzukii is attracted to fermentation volatiles in search of (protein-rich) food and to fruit volatiles in search of oviposition substrates. Winter morph and starved females displayed indiscriminating olfactory behaviour. In the field preference experiment, the hypothesised seasonal shift between fermentation and fruit cues was confirmed. This shift appeared to be highly temperature-related and was similarly observed for summer and winter morphs

Distribution and genetic diversity of the invasive pest Halyomorpha halys (Hemiptera, Pentatomidae) in Belgium

The brown marmorated stink bug, Halyomorpha halys, native to East Asia, is an invasive pest of economic importance. It has invaded North America and many European countries and is further expanding its range. In Belgium, it was first observed in 2011. Halyomorpha halys is known to cause severe damage in commercial fruit orchards and vegetable crops. A dramatic and unmitigated expansion of H. halys in its adventive range could lead to significant economic implications for agricultural production. In this study, occurrence data of H. halys since its first observation in Belgium was analysed together with molecular information to map the populations and evaluate the genetic diversity of this pest. The genetic diversity of H. halys in Belgium was compared to data from other invaded and native countries reported in previous studies to identify possible invasion routes. The analysis of 1176-bp of mitochondrial DNA cytochrome c oxidase I and II genes (COI and COII) led to the discovery of two novel COI-COII haplotype combinations currently unique to Belgium. The invasion of H. halys in Belgium is likely the result of multiple and ongoing introductions from its native region and from already invaded countries in Europe, particularly Italy. The expansion of the brown marmorated stink bug populations in Belgium is recent and ongoing. Presently, it appears to thrive best in northern Belgium

The falling tide algorithm: A new multi-objective approach for complex workforce scheduling

We present a hybrid approach of goal programming and meta-heuristic search to find compromise solutions for a difficult employee scheduling problem, i.e. nurse rostering with many hard and soft constraints. By employing a goal programming model with different parameter settings in its objective function, we can easily obtain a coarse solution where only the system constraints (i.e. hard constraints) are satisfied and an ideal objective-value vector where each single goal (i.e. each soft constraint) reaches its optimal value. The coarse solution is generally unusable in practise, but it can act as an initial point for the subsequent meta-heuristic search to speed up the convergence. Also, the ideal objective-value vector is, of course, usually unachievable, but it can help a multi-criteria search method (i.e. compromise programming) to evaluate the fitness of obtained solutions more efficiently. By incorporating three distance metrics with changing weight vectors, we propose a new time-predefined meta-heuristic approach, which we call the falling tide algorithm, and apply it under a multi-objective framework to find various compromise solutions. By this approach, not only can we achieve a trade off between the computational time and the solution quality, but also we can achieve a trade off between the conflicting objectives to enable better decision-making

The first characterised wheat (Triticum aestivum L.) member of the nudix hydrolase family shows specificity for NAD(P)(H) and FAD

We cloned the first nudix hydrolase of wheat (Triticum aestivum L.) (TaNUDT1) and expressed it using Escherichia coli as expression host. Properties of the purified His6-tagged protein were studied. The sequence codes for a nudix hydrolase with a molecular mass of around 43x103 and a predicted pI of 5.68. The characteristic residues of the nudix box were highly conserved in the wheat enzyme sequence, and TaNUDT1 is most probably targeted to the peroxisomes. In the presence of dithiothreitol and MnCl2, the enzyme hydrolyses the nicotinamide coenzymes NAD(P)(H) as could be predicted by the presence of a conserved amino acid array C-terminal to the nudix box, and the enzyme has higher affinity towards the reduced forms of the coenzymes. In light of previous reports of nudix enzymes and the physiological concentration of their substrates, we found its Km values towards some of the coenzymes to be relatively high. As NAD(P)(H) and FAD play crucial roles in cell metabolism, extensive hydrolysis could be detrimental to cell functioning. We speculate that a decreased enzyme affinity may point to a built-in restriction on coenzyme hydrolysis in vivo. Furthermore, by hydrolysing the cofactors of several redox enzymes, this enzyme may well affect several wheat based processes.status: publishe

Dynamics of gamma-aminobutyric acid in wheat flour bread making

The dynamics of the health-improving non-protein amino acid c-aminobutyric acid (GABA) during bread making were studied. Wheat flour contains trace levels of GABA (<15 ppm) and ca. 160–175 ppm of its precursor, glutamic acid (GA). During dough mixing, the levels of both GA and GABA largely increased. While wheat flour endogenous glutamic acid decarboxylase (GAD) performs some minor conversion of GA into GABA, yeast is the main contributor to GABA formation. Comparison of amino acid levels of dough samples, without or with yeast, indicated that yeast favours both GA and GABA formation already during mixing. Fermentation decreased both GA and GABA contents, due to amino acid consumption by the yeast, which used more GA than GABA. Proofing and baking resulted in large GABA losses, the latter probably in Maillard browning reactions during baking. Thermal loss of GA was less pronounced than that of GABA. Breads contained only trace levels of GABA and ca. 90–130 ppm of its precursor. Exogenous supplementation of recombinantly produced GAD of Yersinia intermedia decreased GA levels in mixed and fermented dough and increased GABA levels. The highest GAD dosage used resulted in fermented doughs with ca. 300 ppm of GABA, i.e. three times higher than the level present in the reference sample (no GAD added). After baking, a significant GABA level was left in the bread samples (ca. 115 ppm) and GABAenriched breads were obtained. Addition of sodium glutamate (100–380 ppm) to a bread recipe containing no added GAD clearly indicated that its precursor was not the limiting factor for GABA conversion during bread making since the resulting breads contained no GABA, or only trace levels (ca. 20 ppm).status: publishe

Mutational analysis of wheat (Triticum aestivum L.) nucleotide pyrophosphatase/phosphodiesterase shows the role of six amino acids in the catalytic mechanism

Nucleotide pyrophosphatases/phosphodiesterases (NPPs, PF01663) release nucleoside 5′-monophosphates from a wide range of nucleotide substrates. Only very recently, the first plant members of the NPP family were characterised (Joye et al. J Cereal Sci 51: 326–336, 2010), and little is known about their substrate-specifying residues. We elucidated the role of six amino acid residues of the recently identified and characterised Triticum aestivum L. NPP (Joye et al. J Cereal Sci 51: 326–336, 2010). Substitution of the highly conserved catalytic Thr132 into Ser or Ala completely abolished enzyme activity. Mutation of a highly conserved His255 residue into an apolar Ala suprisingly increased enzyme activity against most phosphodiester substrates. Four other residues moderately to highly conserved over NPPs of different organisms were studied as well. Mutation of the Asn153, Asn165 and Glu199 into an Arg, Ser and Asp residue, respectively, increased the relative enzyme activity against p-nitrophenyl phosphate. Furthermore, mutation of Phe194 into Ser increased the relative enzyme activity against adenosine 5′-monophosphate-containing substrates, although the overall enzyme activity of this mutant enzyme decreased. We conclude that the structural requirements and the conservation of the amino acids of the catalytic site of TaNPPr and, by extension, probably of all NPPs, are very stringent.status: publishe

Cloning and characterization of two endoxylanases from the cereal phytopathogen Fusarium graminearum and their inhibition profile against endoxylanase inhibitors from wheat

Two genes encoding family 11 endo-beta-1,4-xylanases (XylA, XylB) from Fusarium graminearum were cloned and expressed in Escherichia coli. The amount of active endoxylanase in the cytoplasmic soluble fraction was considerably improved by varying different expression parameters, including host strain and temperature during induction. Both recombinant endoxylanases showed a temperature optimum around 35 degrees C and neutral pH optima (around pH 7 and 8 for XylB and XylA, respectively). For the first time this allowed one to test endoxylanases of a phytopathogenic organism for inhibition by proteinaceous endoxylanase inhibitors TAXI and XIP. Whereas XylA and XylB were inhibited by TAXI-I, no inhibition activity could be detected upon incubation with XIP-I. The insensitivity of both F. graminearum endoxylanases towards XIP is surprising, since the latter is typically active against endoxylanases produced by (aerobic) fungi. As F. graminearum is an important phytopathogen, these findings have implications for the role of endoxylanase inhibitors in plant defence.status: publishe