The dual effects of root-cap exudates on nematodes: from quiescence in plant-parasitic nematodes to frenzy in entomopathogenic nematodes

Abstract

Highlight textPlant defences against root antagonists invigorate root protagonists. The same root-cap exudate impairs the mobility of plant-parasitic nematodes and increases the performances of insect-killing nematodes.

Prospects in the Application Technology and Formulation of Entomopathogenic Nematodes for Biological Control of Insect Pests

“…As glycerol induced a state of dormancy in S. feltiae, the EPN survived prolonged exposure to room temperature up to 180 days without noticeable reduction of their survival (Chen & Glazer, 2005). Such dormancy has also been observed when the EPNs are in contact with certain root exudates (Hiltpold et al, 2015). In addition to the improvement of shelf life at room temperature, the EPN infectiousness was enhanced once the state of dormancy was broken (Hiltpold et al, 2015).…”

“…Both techniques can be used to release EPNs in the field. Signaling chemicals can be added to the alginate solution to interfere with the insect pest behavior and use the alginate structure as a Trojan Horse or possibly boost the EPN effectiveness (Hiltpold, Jaffuel, & Turlings, 2015) (Drawing: I. Hiltpold) of alginate containing hyphae of the endoparasitic nematophagous fungi Hirsutella rhossiliensis Minter & Brady (Deuteromycotina: Hyphomycetes) were produced to successfully control plant-parasitic nematodes in microcosms (Lackey, Muldoon, & Jaffee, 1993).…”

“…Such dormancy has also been observed when the EPNs are in contact with certain root exudates (Hiltpold et al, 2015). In addition to the improvement of shelf life at room temperature, the EPN infectiousness was enhanced once the state of dormancy was broken (Hiltpold et al, 2015). Encapsulation of EPNs still needs improvements, yet, this approach has some very good potential as it simplifies nematode transport, storage, handling and application, and saves substantial amounts of water, a critical resource in agriculture.…”

“…Plants can be genetically engineered to enhance the production of certain volatiles, thereby favoring insect pest control with EPNs (Degenhardt et al, 2009). Particular root exudates have been shown to have a dual effect in the rhizosphere, subduing plant pathogenic nematodes while invigorating EPNs (Hiltpold et al, 2015). While concentrated root-tip exudates of green pea, Pisum sativum L. (Fabales: Fabaceae) induced quiescence in several EPN species, lower concentrations, likely to be encountered in the rhizosphere, did not induce quiescence in EPNs but significantly increased their activity and infectiousness (Hiltpold et al, 2015).…”

“…Particular root exudates have been shown to have a dual effect in the rhizosphere, subduing plant pathogenic nematodes while invigorating EPNs (Hiltpold et al, 2015). While concentrated root-tip exudates of green pea, Pisum sativum L. (Fabales: Fabaceae) induced quiescence in several EPN species, lower concentrations, likely to be encountered in the rhizosphere, did not induce quiescence in EPNs but significantly increased their activity and infectiousness (Hiltpold et al, 2015). Incorporating such chemicals into the EPN formulations under development, including alginate capsules (see description above), has the potential to improve EPN shelf life due to reduced metabolic rates in quiescent EPNs (more lipids were measured in EPNs stored in root exudate than in EPNs stored in water).…”