Effect of small lipophilic molecules in tomato and rice root exudates on the behaviour of Meloidogyne incognita and M. graminicola

Abstract

Plant chemicals in the rhizosphere originating from root exudates or sites of previous nematode penetration can influence nematode behaviour, and a number of plant compounds, some present in root exudates, have been shown either to attract nematodes to the roots, or to result in repellence, motility inhibition, or even death. The present work was conducted to isolate small lipophilic molecules (SLMs) emitted by root exudates of Solanum lycopersicum and Oryza sativa to investigate their effect on root-knot nematodes. SLMs extracted, through solid phase extraction, from hydroponically collected root exudates of 40 tomato and rice plants had an inhibitory impact on the motility of second-stage juveniles of Meloidogyne incognita and M. graminicola and showed a nematotoxic or nematostatic (upon dilution) effect on both species. The semiochemicals present in the SLMs induced a very small, albeit statistically significant, effect on stylet thrusting. A small quantity of salivary secretion around the stylet tip and a significant decrease in nematode head movement were observed. The semiochemicals negatively influenced behaviour of M. incognita and M. graminicola by strongly affecting their mobility. Therefore, it is proposed that SLMs present in both tomato and rice root exudates play important roles during the interaction of Meloidogyne spp. with their host plant, and that they might exert a repellent, or allellopathic, effect on these nematodes.

Transcriptomic and histological responses of African rice (Oryza glaberrima) to Meloidogyne graminicola provide new insights into root-knot nematode resistance in monocots

“…J2s are attracted towards the plant by root exudates, but some compounds may have nematotoxic or nematostatic effects (Curtis et al, 2009;Dutta et al, 2012). Although it is known that rice roots produce small lipophilic molecules that can repel M. graminicola (Dutta et al, 2012), no data are currently available about nematode chemoattraction to Gene expression levels were measured by RT-qPCR assays and normalized using three internal reference genes: OsEIF5C, OsREF3 and OsEXPNAR. Data shown are relative transcript levels compared with control roots of water-sprayed plants (expression level set at 1).…”

Inhibitory effects of components from root exudates of Welsh onion against root knot nematodes

“…For example, analysis of tomato root exudates indicates that four compounds, namely 2,6-di- tert -butyl- p -cresol, L -ascorbyl 2,6-dipalmitate, dibutyl phthalate, and dimethyl phthalate, were capable of suppressing Meloidogyne incognita eggs from hatching and were associated with increased J2 mortality [19]. Dutta [20] observed that small lipophilic molecules present in the root exudates of tomato and rice negatively affect Meloidogyne spp. mobility.…”

Resistance Mechanisms of Tomato (Solanum lycopersicum) to Root-Knot Nematodes (Meloidogyne species)

“…SLMs were extracted through solid phase extraction and bioasssays were developed to test nematode stylet thrusting, motilty, imobility and mortality. The result showed that a significant decrease in stylet thrusting, nematode head movement and reduction in salivary secretion of Meloidogyne graminicola and M. incognita J2 (Dutta et al, 2012). It has also been observed that SLM inhibits the motility of J2.…”

“…(Molinari and Baser, 2010). Plant secondary metabolites influence the behaviour of root-knot nematodes (Campos et al, 2012;Dutta et al, 2012). A study was conducted to investigate the effect of small lipophilic molecules (SLM), root exudates of S. lycopersicum, on RKN.…”