Abstract
Plant-parasitic-nematodes represent a major threat to the agricultural production of different crops worldwide. Due to the high toxicity of chemical nematicides, it is necessary to develop new control strategies against nematodes. In this respect, filamentous fungi can be an interesting biocontrol alternative. The genus Trichoderma, mycorrhizal and endophytic fungi are the main groups of filamentous fungi studied and used as biological control agents (BCAs) against nematodes as resistance inducers. They are able to reduce the damage caused by plant-parasitic nematodes directly by parasitism, antibiosis, paralysis and by the production of lytic enzymes. But they also minimize harm by space and resource-competition, by providing higher nutrient and water uptake to the plant, or by modifying the root morphology, and/or rhizosphere interactions, that constitutes an advantage for the plant-growth. Besides, filamentous fungi are able to induce resistance against nematodes by activating hormone-mediated (salicylic and jasmonic acid, strigolactones among others) plant-defense mechanisms. Additionally, the alteration of the transport of chemical defense components through the plant or the synthesis of plant secondary metabolites and different enzymes can also contribute to enhancing plant defenses. Therefore, the use of filamentous fungi of the mentioned groups as BCAs is a promising durable biocontrol strategy in agriculture against plant-parasitic nematodes.
Highlights
Over 4100 species of plant-parasitic nematodes were described to date, among which, a restricted group of genera is considered as major plant-pathogens, whereas others are specific to a more limited range of crops, both causing a high impact to economically important crops
There are many examples described in the literature, among which we find for example Odontopharynx longicaudata, effective against M. incognita and M. javanica and M. gaugleri, effective against Heterodera oryzae and M. incognita
This systemic defense stimulation prepares the immune response of the plant, allowing a faster response after the priming against the subsequent attack of any kind of pathogen and reducing the possibility of disease spread (Hermosa et al, 2012; Bisen et al, 2016; Mendoza-Mendoza et al, 2018). This induced systemic resistance (ISR) is regulated by a jasmonic acid (JA)/ET signaling, as described by Leonetti et al (2014). They observed that salicylic acid (SA) signaling is down-regulated in the early stages of M. javanica infection in tomato roots while, the response mediated by JA/ET is induced in tomato roots treated with the fungus, which indicates that the presence of Trichoderma activates the ISR within the plant
Summary
Over 4100 species of plant-parasitic nematodes were described to date, among which, a restricted group of genera is considered as major plant-pathogens, whereas others are specific to a more limited range of crops, both causing a high impact to economically important crops. Endophytic fungi are able to induce in plants SAR and ISR against the attack of pests and/or pathogens, but they need to suppress, at least partially, the defenses of the plants to be able to colonize their tissues (Busby et al, 2016).
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