Bioactive Volatiles from an Endophytic Daldinia cf. concentrica Isolate Affect the Viability of the Plant Parasitic Nematode Meloidogyne javanica

PLoS One. 2016 Dec 20;11(12):e0168437. doi: 10.1371/journal.pone.0168437. eCollection 2016.

Abstract

Plant-parasitic nematodes form one of the largest sources of biotic stress imposed on plants, and are very difficult to control; among them are the obligate parasites, the sedentary root-knot nematodes (RKNs)-Meloidogyne spp.-which are extremely polyphagous and exploit a very wide range of hosts. Endophytic fungi are organisms that spend most of their life cycle within plant tissue without causing visible damage to the host plant. Many endophytes secrete specialized metabolites and/or emit volatile organic compounds (VOCs) that exhibit biological activity. Recently, we demonstrated that the endophytic fungus Daldinia cf. concentrica secrets biologically active VOCs. Here we examined the ability of the fungus and its VOCs to control the RKN M. javanica both in vitro and greenhouse experiments. The D. cf. concentrica VOCs showed bionematicidal activity against the second-stage juveniles (J2s) of M. javanica. We found that exposure of J2s to fungal volatiles caused 67% reduction in viability, and that application of a synthetic volatile mixture (SVM), comprising 3-methyl-1-butanol, (±)-2-methyl-1-butanol, 4-heptanone, and isoamyl acetate, in volumetric ratio of 1:1:2:1 further reduced J2s viability by 99%. We demonstrated that, although each of the four VOCs significantly reduced the viability of J2s relative to the control, only 4-heptanone elicited the same effect as the whole mixture, with nematicidal activity of 90% reduction in viability of the J2s. Study of the effect of the SVM on egg hatching demonstrated that it decreased eggs hatching by 87%. Finally, application of the SVM to soil inoculated with M. javanica eggs or J2s prior to planting susceptible tomato plants resulted in a significantly reduced galling index and fewer eggs produced on each root system, with no effect on root weight. Thus, D. cf. concentrica and/or SVM based on fungal VOCs may be considered as a novel alternative approach to controlling the RKN M. javanica.

MeSH terms

  • Animals
  • Antinematodal Agents / chemistry
  • Antinematodal Agents / pharmacology*
  • Nematoda / growth & development*
  • Plant Diseases / parasitology*
  • Solanum lycopersicum / parasitology*
  • Volatile Organic Compounds / chemistry
  • Volatile Organic Compounds / pharmacology*
  • Xylariales / chemistry*

Substances

  • Antinematodal Agents
  • Volatile Organic Compounds

Grants and funding

This work was financed by the Chief Scientist of Israel's Ministry of Agriculture and Rural Development (MOARD) (https://agriscience.co.il), under grant number 132-1252-06, and the Chief Scientist of Israel's Ministry of Economy (http://www.matimop.org.il/ocs.html), under grant number 47106 ("Kamin project"). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The grants were given to D.E.