Validation of the Chemotaxis of Plant Parasitic Nematodes Toward Host Root Exudates

Wenshan Liu,Kathy S Lawrence,Sang-Wook Park,Heather N Gosse,Alexis L Jones

doi:10.21307/jofnem-2019-063

Abstract

Plant parasitic nematodes (PPN) are microscopic soil herbivores that cause damage to many economic crops. For the last century, it has been proposed that chemotaxis is the primary means by which PPN locate host plant roots. The identities and modes of action of chemoattractants that deliver host-specific messages to PPN, however, are still elusive. In this study, a unique multidimensional agar-based motility assay was developed to assess the impacts of root exudates on the short-range motility and orientation of PPN. Three PPN (Rotylenchulus reniformis, Meloidogyne incognita and Heterodera glycines) and root exudates from their respective host and non-host plants (cotton, soybean, and peanut) were used to validate the assay. As predicted, R. reniformis and M. incognita were attracted to root exudates of cotton and soybean (hosts), but not to the exudates of peanut (non-host). Likewise, H. glycines was attracted to soybean (host) root exudates. These results underpinned the intrinsic roles of root exudates in conveying the host specificity of PPN. In particular, PPN selectively identified and targeted to hydrophilic, but not hydrophobic, fractions of root exudates, indicating that groundwater should be an effective matrix for chemotaxis associated with PPN and their host plant interactions.

Highlights

Plant parasitic nematodes (PPN) are microscopic soil herbivores that cause damage to many economic crops
To validate and optimize the PPN motility assay, we first tested it in assessing the responsive behaviors of R. reniformis toward root extracts prepared from its host or non-host plants (Fig. 2A and B)
Most R. reniformis (> 99%) moved down and migrated away from the volcano deck when root extracts of three peanut varieties were examined (Fig. 2A and B). These results elucidated that PPN are chemotactic toward metabolites produced in host plant roots, and can move actively and autonomously toward chemoattractants

Summary

Introduction

Plant parasitic nematodes (PPN) are microscopic soil herbivores that cause damage to many economic crops. PPN develop longitudinal muscles and a thick cuticle as a hydrostatic skeleton, necessary for their locomotion, and are commonly thought to move through the soil a distance of ~1 m within their lifetime (Davis and MacGuidwin, 2005; Moore et al, 2010) It is still elusive whether the movement of PPN is autonomous or governed by environmental matrices such as water, insects, and/ or animals, and is random or target specific toward chemoattractants associated with host plants. (pluronic F-127), natural sand and soil as migration matrices, and elucidated that PPN are responsive to plant roots, pH, redox potentials, temperature, moisture, carbon dioxide, oxygen, and inorganic ions (reviewed in Prot, 1980; Perry, 1996; Curtis, 2008; Fosu-Nyarko and Jones, 2016) These studies, have failed to explain the host specificity of PPN, and argued that plant and PPN interactions are not selective in general (Prot, 1980). The nematodes were able to engage in pathogenicity, mobility, and environmental stability (Hiltpold et al, 2015)

Methods

Results

Conclusion