Perspectives de lutte contre les maladies des arbres fruitiers à pépins au moyen de substances naturelles inductrices d'une résistance systémique

Biotechnologie, Agronomie, Société et Environnement 01/2002;
Source: DOAJ


Natural compounds used as elicitors of systemic induced resistance offer new prospects to control pome fruit tree diseases. This review presents a new way of plant protection for pome fruit tree diseases as a potential response to the very high use of pesticides in commercial production with the view to reduce their negative side-effects on environment and human health. Work is focused on examples of use of elicitors from natural origin which induce systemic resistance for controlling two important diseases as apple scab (Venturia inaequalis) and fire blight (Erwinia amylovora). Many factors limit today their practical use: their efficacy is only partial and in interaction with plants and environment; much work has to be done to improve the formulation and to determine doses and rates of application, the right phenologic application times, and finally they are often submitted to the normal high standards of Plant Protection Products Regulations which are long, very expensive and not adapted to compounds which can have a very complex composition. In other hands, this new way of plant protection presents many potential advantages: using relatively simple, not expensive, non toxic natural compounds with a good image; polyvalent and broad field of action; non-specific and multi-side action which offer a good durability of action; systemic action in the plants during a relative long period of time and the possibility to control difficult bacterial diseases and more surprisingly viral diseases. The multiple advantages presented offer valuable prospects for a better friend-environmentally way to control pome fruit diseases in the next future.

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    • "The pathogen in many cases will die when this happens, due to toxic substances accumulating in the dead plant cells (MacHardy, 1996). Lateur (2002) listed the most common metabolic modifications for an induced resistance mechanism as (a) the reinforcement of the mechanical barrier consisting of a pecto-cellulose wall by incorporation of polysaccharides (callose), phenolic polymers (lignine), polyesters (suberine), and proteins (van Loon, 1997), (b) the stimulation of defense enzymes, and (c) the production of defense and pathogenesis related proteins, such as chitinases, glucanases, and thaumatinelike proteins. All these factors may influence the reflectance spectra and therefore make it theoretically possible to identify stress in apple plants by comparing spectra of infected and noninfected leaves. "
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    ABSTRACT: The use of hyperspectral approaches for early detection of plant stress caused by Venturia inaequalis (apple scab) was investigated to move towards more efficient and reduced application of pesticides, fertilizers or other crop management treatments in apple orchards. Apple leaves of the resistant cultivar, Rewena and the susceptible cultivar, Braeburn, were artificially inoculated with conidia of V. inaequalis in a controlled greenhouse environment. The research focused on (i) determining if leaves infected with V. inaequalis could be differentiated from non-infected leaves, (ii) investigating at which developmental stage V. inaequalis infection could be detected, and (iii) selecting wavelengths that best differentiated between infected and non-infected leaves. Hyperspectral data were used because of their contiguous nature and the abundance of narrow wavelength bands in the electromagnetic reflectance spectrum, thereby providing the spectral sensitivity needed to detect subtle variations in reflectance. Processing the data, however, presented challenges, given the need to avoid data redundancy, identification of data extraction techniques, and maintaining modeling accuracy. Statistical techniques therefore had to be robust. Logistic regression, partial least squares logistic discriminant analysis, and tree-based modeling were used to select the hyperspectral bands that best defined differences among infected and non-infected leaves. Results suggested that good predictability (c-values > 0.8) could be achieved when classifying infected plants based on these supervised classification techniques. It was concluded that the spectral domains between 1350–1750 nm and 2200–2500 nm were the most important regions for separating stressed from healthy leaves immediately after infection. The visible wavelengths, especially around 650–700 nm, increased in importance three weeks after infection at a well-developed infection stage. Identification of such critical spectral regions constitutes the logical first step towards development of robust stress indicators based on hyperspectral imagery.
    Full-text · Article · Jul 2007 · European Journal of Agronomy
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    • "Among these phenylpropanoids synthesised are lignins and salicylic acid. Lignins reinforce pectocellulosic cell walls and limit the invasion of plant tissues by pathogens (Pautot et al., 1999;Lateur, 2002); while salicylic acid plays a fundamental role in signaling plant defense against pathogens (Martinez et al., 2000). Accumulation of this molecule in the plant or its application on plant tissues induces the synthesis of phenylalanine ammonia-lyase (PAL, EC, "
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    ABSTRACT: Plants respond to attack by pathogens by initiating a change in cellular metabolism, leading to synthesis of antifungal proteins, production of phytoalexins and/or accumulation of phenolic compounds, namely lignins and salicylic. Lignins reinforce pectocellulosic cell walls and limit the invasion of plant tissues by pathogens; while salicylic acid plays a role in signals plant defense against pathogens. The objective of this study was to evaluate the activities of phenylalanine ammonia-lyase (PAL, EC and tyrosine ammonia-lyase (TAL, EC; and to determine the level of their involvement in the biosynthetic pathway of these phenylpropanoids in cells of cassava (Manihot esculenta Crantz, cv Yacé) elicited with salicylic acid (SA). PAL and TAL activities were demonstrated in crude extract enzyme. PAL activity was 9.8 times greater than that of TAL in the pellet obtained with 20% (w/v) ammonium sulphate. In the extract treated with Dowex 2 (cationic), TAL activity was 36.7 times greater than that of PAL. pH and temperature optima of PAL (8; 40 °C) differed from those of TAL (8.5; 30 °C). In the presence of SA, PAL and TAL activities were respectively maximum 24 and 72 hr after inoculation. TAL activity and induced phenols were much higher than PAL. PAL and TAL activities were optimised respectively, by 75 and 100 µM of SA. The synthesis of phenolic compounds was concomitant with enzymes stimulation. These results show that PAL is different from TAL and the two enzymes are involved in the biosynthetic pathway of phenylpropanoids in cassava.
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    ABSTRACT: The potential yield of (capital)-intensive multi-annual crops (e.g., fruit) is seldom harvested in real- ity. A targeted monitoring and modelling of the growth processes in such agricultural production systems could enable an early detection and treatment of production limiting factors, thereby opti- mising yield. In Belgium, as in all temperate regions, scab stress caused by the ascomycete Ven- turia Inaequalis causes the most important stress in apple orchards. The objectives of this study were (i) to determine if Venturia inaequalis leaf infections could be differentiated from healthy leaves in both resistant and susceptible cultivars using hyperspectral spectroradiometer data, (ii) to gauge at which developmental stage Venturia inaequalis infections could be detected and (iii) to identify wavelengths or spectral regions that best differentiate between infected and healthy leaf material. The first objective was related directly to the scientific research question of whether or not infected leaves resulted in a spectral response different from healthy leaves. The second objective addressed the question of whether or not hyperspectral data could serve as part of an early warn- ing system to biotic stress in apple orchards, while the last objective defines the practical implica- tion of such a spectral warning system. Partial Least Squares Discriminant Analysis (PLSDA) was used as classification technique. This technique compresses the dimension of the hyperspectral reflectance dataset, followed by a discriminant classification. Results suggested that good predict- ability could be achieved when classifying infected plants based on hyperspectral data using PLSDA. Furthermore, a band reduction technique based on logistic regression was used to select the hyperspectral bands that best define differences among treatments. This study showed that the spectral domains centered around 1500nm and the visible region (well-developed infection stage) were best suited to differentiate between infected and healthy plants.
    Full-text · Conference Paper · Jan 2005
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