1,721,123 research outputs found
Induced systemic resistance against systemic viruses : a feasible approach?
Full text linkInduction of resistance to plant viruses causing localized infections has been widely used to
study HR and SAR mechanisms. However, in Nature true virus diseases are produced by viruses able
to systemize in the plant and SAR is scarcely effective against them. Thus, a more successful strategy
relays in the induction of resistance against both the virus and its vector. In this work, using the
pathosystem bean common mosaic virus (BCMV)-Phaseolus vulgaris we made attempts of inducing
resistance separately to both the pathogen and the aphid vector Myzus persicae, with the aim of
dissecting the two resistance levels inducible with the most used chemical elicitors. Results showed
that BTH and chitosan are able to reduce the infection degree in BCMV mechanically inoculated
plants, however not preventing the infection. On the other hand, chitosan and 2-isobutyric acid (IBA),
applied as root-drench, could reduce aphid population by half. Therefore, combining the two effects
and using chitosan, partially effective against both the virus and the vector, it could be possible to raise
an acceptable resistance level in the field, where BCMV is actively spread by aphids. To verify this
hypothesis, experimental transmission with viruliferous aphids in chitosan and IBA treated plants are
now in progress
Review of innate and specific immunity in plants and animals
No full textInnate immunity represents a trait common to plants and animals, based on the recognition of pathogen associated molecular patterns (PAMPs) by the host pattern recognition receptors (PRRs). It is generally assumed that a pathogen strain, or race, may have elaborated mechanisms to suppress, or evade, the PAMP-triggered immunity. Once this plan was successful, the colonization would have been counteracted by an adaptive strategy that a plant cultivar must have evolved as a second line of defence. In this co-evolutionary context, adaptive immunity and host resistance (cultivar-pathogen race/strain-specific) has been differently selected, in animals and plants respectively, to face specialized pathogens. Notwithstanding, plant host resistance, based on matching between resistance (R) and avirulence (avr) genes, represents a form of innate immunity, being R proteins similar to PRRs, although able to recognize specific virulence factors (avr proteins) rather than PAMPs. Besides, despite the lack of adaptive immunity preserved plants from autoimmune disorders, inappropriate plant immune responses may occur, producing some side-effects, in terms of fitness costs of induced resistance and autotoxicity. A set of similar defence responses shared from plants and animals, such as defensins, reactive oxygen species (ROS), oxylipins and programmed cell death (PCD) are briefly described
Systemic acquired resistance (50 years after discovery): Moving from the lab to the field
No full textInduction of plant defense(s) against pathogen challenge(s) has been the object of progressively more intense research in the past two decades. Insights on mechanisms of systemic acquired resistance (SAR) and similar, alternative processes, as well as on problems encountered on moving to their practical application in open field, have been carefully pursued and, as far as possible, defined. In reviewing the number of research works published in metabolomic, genetic, biochemical, and crop protection correlated disciplines, the following outline has been adopted: 1, introduction to the processes currently considered as models of the innate immunity; 2, primary signals, such as salicylic acid (SA), jasmonic acid (JA), and abscisic acid (ABA), involved with different roles in the above-mentioned processes; 3, long-distance signals, identified from petiole exudates as mobile signaling metabolites during expressed resistance; 4, exogenous inducers, including the most significant chemicals known to stimulate the plant resistance induction and originated from both synthetic and natural sources; 5, fungicides shown to act as stimulators of SAR in addition to their biocidal action; 6, elusive mechanism of priming, reporting on the most recent working hypotheses on the pretranscriptional ways through which treated plants may express resistance upon pathogen attack and how this resistance can be transmitted to the next generation; 7, fitness costs and benefits of SAR so far reported from field application of induced resistance; 8, factors affecting efficacy of induced resistance in the open field, indicating that forces, unrevealed under controlled conditions, may be operative in the field; 9, concluding remarks address the efforts required to apply the strategy of crop resistance induction according to the rules of integrated pest management
Cell death or not cell death : two different mechanisms for chitosan and BTH antiviral activity
No full textFitness costs of chemically-induced resistance: double edged sword or (un)stable equilibrium?
No full textL’avvizzimento del nocciolo : rischio reale o remota possibilità di introduzione in Italia?
No full textBenzothiadiazole (BTH) induces cell-death independent resistance in Phaseolus vulgaris against Uromyces appendiculatus
No full textBenzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), trade name Bion(R), was used to induce resistance in bean cultivars Borlotto Nano Lingua di Fuoco (BLF), Borlotto Taylor, Cannellino, Cannellino Montalbano, Saxa and Top Crop, against rust caused by Uromyces appendiculatus. A single 0.3 mm BTH spray 7 days before inoculation was sufficient to fully control the disease in all the examined cultivars. As regards the more susceptible BLF, either a single treatment 14 days before inoculation, or three applications on the third, fifth and seventh day before inoculation, were equally effective to prevent infection. Histochemical and cytochemical investigations showed that BTH causes hydrogen peroxide (H2O2) accumulation in the treated tissues. H2O2 deposits were localized in situ for the first time in the apoplast of the leaf epidermis. No cell death was detected at BTH concentrations below the phytotoxicity threshold, suggesting that acquired resistance against bean rust is mainly related to the enhanced activity of anionic peroxidases, promoted by H2O2 accumulation, thereby leading to cell wall strengthening. This hypothesis is also supported by the long induction phase required to establish complete resistance
Dose-dependent effects of exogenous melatonin on the plant response to biotic and abiotic stresses
No full textIs modulating virus virulence by induced systemic resistance realistic?
No full textInduction of plant resistance, either achieved by chemicals (systemic acquired resistance, SAR) or by rhizobacteria (induced systemic resistance, ISR) is a possible and/or complementary alternative to manage virus infections in crops. SAR mechanisms operating against viruses are diverse, depending on the pathosystem, and may inhibit virus replication as well as cell-to-cell and long-distance movement. Inhibition is often mediated by salicylic acid with the involvement of alternative oxidase and reactive oxygen species. However, salicylate may also stimulate a separate downstream pathway, leading to the induction of an additional mechanism, based on RNA-dependent RNA polymerase 1-mediated RNA silencing. Thus, SAR and RNA silencing would closely cooperate in the defence against virus infection. Despite tremendous recent progress in the knowledge of SAR mechanisms, only a few compounds, including benzothiadiazole and chitosan have been shown to reduce the severity of systemic virus disease in controlled environment and, more modestly, in open field. Finally, ISR induction, has proved to be a promising strategy to control virus disease, particularly by seed bacterization with a mixture of plant growth-promoting rhizobacteria. However, the use of any of these treatments should be integrated with cultivation practices that reduce vector pressure by the use of insecticides, or by Bt crops
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