Advances in induced resistance by natural compounds: towards new options for woody crop protection

Abstract

The activation of defensive responses of plants is a promising tool for controlling pests in conventional agriculture. Over the last few years, several compounds have been studied to protect crops from pests, without displaying direct toxicity for pathogenic organisms. These compounds have the ability to induce a priming state on the plants that results in resistance (or tolerance) against subsequent infection by a pathogen. In terms of molecular response, induced plant defense involves a broad number of physical and biochemical changes such as callose deposition or phenolic compounds, activation of salicylic and/or jasmonic acid pathways or synthesis of defense-related enzymes. Despite the large number of studies performed to ascertain the physiological and biochemical basis of induced resistance, only a few resistance-activating compounds have been studied as a real alternative to classic means of control and the studies geared towards incorporating induced resistance into disease management programs are relatively rare. The incorporation of natural resistance inducer in pest management programs of woody crops, alone or in combination with classical methods, could be a reliable method for reducing the amount of chemical residues in the environment. In this review, we discuss the current knowledge of induced resistance in woody crops, focusing on the mode of action of compounds authorized for conventional agriculture. We conclude by discussing the environmental and economic advantages of applying resistance inducers to conventional agriculture with special emphasis on natural compounds.

Elucidating the mechanism of action of copper heptagluconate on the plant immune system against Pseudomonas syringae in tomato (Solanum lycopersicum L)

“…Likewise, it has been demonstrated that application of some natural and chemical compounds induces a plant's innate resistance and this, usually, is enough to overcome the stress and survive . Moreover, some resistance‐inducers have shown a persistent effect for up to several months, which may help to reduce the amount of residues in vegetables and fruits …”

“…11,12 Moreover, some resistance-inducers have shown a persistent effect for up to several months, which may help to reduce the amount of residues in vegetables and fruits. 13,14 The study of new compounds based on organic formulations of Cu and their dual effect as an inductor of plant innate defences would provide a valuable alternative to farmers for the control of pathogens such as P. syringae. Cu heptagluconate is characterized by great Cu absorption and diffusion over the plant, and is safer for the environment than other traditional inorganic Cu-based fungicides.…”

Antifungal and antioxidant activities of mature leaves of Myrcia splendens (Sw.) DC.

“…The Alternaria brown spot (ABS) is a disease caused by Alternaria alternata that primarily affects the leaves and fruits of tangerine and its hybrids, which results in great losses in production, besides being a disease of difficult control (Carvalho et al, 2011). In one of the few studies evaluating the activity of natural products against the plant pathogen A. alternata, it was found that the essential oil of Piper hispidinervum showed fungitoxic activity on the mycelial growth of this fungus (La Torre et al, 2014;Llorens et al, 2017). Although the inhibitory activity presented by extract 2B in the present study is considered low, it refers to extracts and not to isolated compounds; therefore, subsequent studies with this extract are encouraged.…”

New approaches to control Pseudomonas syringae disease in tomato plants

“…In this way, after stress has been recognised, besides the local response the plant is able to induce defensive responses in systemic tissues by protecting the parts that are still not exposed to damage. In the last years, it has been demonstrated that this enhanced physiological status can also be induced by mild stress, the application of natural and chemical compounds or beneficial microbes, mycorrhiza and endophytes (Pieterse et al, 2000;van Wees et al, 2008;Jung et al, 2012;Bastias et al, 2017;Llorens et al, 2017).…”

“…Likewise, it has been demonstrated that the application of some natural and chemical compounds induces a plant innate resistance that, usually, is enough to overcome the stress and survive . Moreover, some resistant inducers showed a persistent effect up to several months, which can contribute to reduce the amount of residues in the vegetables and fruits (Llorens et al, 2017;.…”