Increased penetration of host roots by nematodes after recovery from quiescence induced by root cap exudate

Abstract

Fourteen of 20 plant species surveyed produced root cap exudates that induced a state of reversible quiescence in Meloidogyne incognita and Caenorhabditis elegans. Exudate from six species failed to induce quiescence in either nematode species. Root cap exudates from pea were found to trigger quiescence in populations of plant-parasitic, animal-parasitic, insect-pathogenic, and free-living nematode species. One animal parasite was resistant. Caenorhabditis elegans strains with defects in known metabolic pathways also were screened to explore the potential for using this model system to examine the genetic basis for exudates-induced quiescence (EIQ). All 62 lines tested exhibited wild type sensitivity to root cap exudates and preliminary efforts to obtain viable EIQresistant strains by ethyl methanesulphonate (EMS) mutagenesis were unsuccessful. After recovery from EIQ, penetration of alfalfa roots by second-stage juveniles of M. incognita more than doubled within 24 h, compared with controls, and the number of nematodes per root remained high for a week but long-term development and maturation was similar to that of untreated control inoculum. In cucumber, penetration after recovery from EIQ increased by several fold but returned to control levels within 4 days post-inoculation.

Small molecules below‐ground: the role of specialized metabolites in the rhizosphere

“…For example, in vitro assays showed that Ditylenchus destructor was attracted to sweet potato crude root exudates (Xu et al, 2015). In addition, water-soluble metabolites exuded from the root tip of green pea (Pisum sativum L.) and maize resulted in a dormancy-like state in nematodes and reduced their infectability (Zhao et al, 2000;Hawes et al, 2005).…”

Plant Root Secretions and Their Interactions with Neighbors

“…For instance, root exudates of cucumber and their fractions having both repellent and attractant activity to M. incognita were reported (Castro et al 1989). Similarly, the root cap exudates that include enzymes, antibiotics, and other soluble chemicals and mucilage repelled both plant parasitic nematodes and free-living nematode Caenorhabditis elegans and resulted in reversible state of immobility in these nematodes (Hubbard et al 2005;Wuyts et al 2006;Zhao et al 2000). This study indicates that the root tip delivered products has the potential to temporarily immobilize nematodes.…”

Root-knot nematode chemotaxis is positively regulated by l -galactose sidechains of mucilage carbohydrate rhamnogalacturonan-I

“…Root exudates from several plant species also attract nematodes. Lauric acid from crown daisy ( Chrysanthemum coronarium L.) can be nematocidic when presented in certain concentrations, while the root cap exudates from several plant species can immobilize nematodes in a reversible fashion ( 13 , 36 ). This suggests that plant exudates are not only used by nematodes for host finding but also may be a mechanism to protect plants from pathogens or even capture prey.…”