Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2020
Publication Date: 7/29/2020
Publication URL: https://handle.nal.usda.gov/10113/7071246
Citation: Kihika, R.; Tchouassi, D.P.; Ng’ang’a, M.M.; Hall, D.R.; Beck, J.J.; Torto, B. Compounds associated with infection by root-knot nematodes influence the ability of infective juveniles to recognize host plants. J. Agric. Food Chem. 2020, 68, 9100-9109. doi.org/10.1021/acs.jafc.0c03386
DOI: https://doi.org/10.1021/acs.jafc.0c03386

Interpretive Summary: The above-ground portions of a plant are known to emit certain odors when the plant is attacked by insects. However, when plants are attacked below-ground by nematodes the odors emitted by the plant's roots are not as well understood. Scientists at the International Centre for Insect Physiology and Ecology (icipe), the University of Greenwich, and the USDA-ARS Center for Medical, Agricultural, and Veterinary Entomology located in Gainesville, FL, investigated the affect infecting tomato roots with the infective-stage juveniles (J2s) of the plant parasitic nematode, Meloidogyne javanica, a pest of several important agricultural crops. Evaluated were the resultant odors emitted by tomato roots, and if other nematodes were influenced by these odors. In behavioral assays, J2 infection of tomato roots influenced the behavior of other M. javanica, and this varied with the time after nematode-infection. Chemical analysis of the odors identified specific chemical compounds, and additional behavioral assays determined how these chemicals affected J2 responses (e.g., attract or inhibit). The results of this study demonstrate that nematode-induced plant odors can provide a potential avenue for management of these destructive nematodes in agricultural systems.

Technical Abstract: Plant volatiles are altered during herbivore or parasite attack and feeding, yet the contribution of plant parasitic nematode (PPN) infection on root volatile emission and interactions with other organisms remains poorly understood. Here, we investigated the influence of the infective stage juveniles (J2s) of the PPN Meloidogyne javanica in inducing tomato root volatiles and in the chemotaxis of conspecifics. In behavioral assays, J2s infection of tomato roots differentially influenced the behavior of conspecifics and this varied with the time after RKN-infection. Chemical analysis showed 2-7-fold increase in the amounts of monoterpenes emitted in the root volatiles of M. javanica-infected than in uninfected roots. The monoterpenes ß-pinene, (+)-(2)-carene, a-phellandrene, ß-phellandrene differentially attracted (51-87%) J2s, whereas concurrent quantitative reduction in the levels of methyl salicylate and an increase in the levels of (Z)-methyl dihydrojasmonate in the root volatiles reduced J2 responses. Our study demonstrates that nematode-induced plant volatiles can provide a potential avenue for management of RKNs.