Trichoderma harzianum-induced defense in sunflower (Helianthus annuus L.) against Plasmopara halstedii with changes in metabolite profiling of roots

ABSTRACT

Sunflower (Helianthus annuus L.), one of the most important oilseed crops worldwide, is greatly damaged by downy mildew disease caused by Plasmopara halstedii. Trichoderma harzianum (TRIC8) isolate, isolated from soils of Tekirdağ/Turkey, was tested to determine its effect on hypocotyl length and sporulation density of the pathogen on cotyledon leaves of seedlings grown in pots. The ability of T. harzianum to induce the accumulation of metabolites in roots during its interaction with the pathogen was also studied using gas chromatography/mass spectrometry (GC/MS). In the experiments, seeds were coated with TRIC8 and the roots of three-day old seedlings were inoculated with P. halstedii. TRIC8 treatment significantly enhanced hypocotyl length as compared with untreated control (sterile distilled water) and fungicide (ai: Metalaxyl-m) treatments; reduced sporulation density of pathogen (76.30%) was comparable to the fungicide (76.55%) in pot experiments. TRIC8 increased the accumulation of heptanoic acid (carboxylic acid), methyl palmitate (ester) and 10,12 octadecadiynoic acid (fatty acid) especially in roots challenged with P. halstedii when compared with untreated control. Additionally, 17 metabolites [an alcohol: Z-2-dodecen-1-ol; an alkyl halide: 1-bromocyclohexane; an amide: N,N'-thylenebis(N-nitroacetamide); an anhydride: trans-(2-octenyl)succinic anhydride; three corbocyclic acids: butanedioic acid, capric acid, 4-hydroxy benzoic acid; a coumarin derivative: 6-tert-butyl-4-methylcoumarin, six esters: ethyl n-heptadecanoate, ethyl linolenate, 2-hydroxyethyl prop-2-enoate, isopropyl phenylacetate, (Z,Z)-5,16-octadecadien-1-ol acetate, undecyl trichloroacetate; a heterocyclic compound: dendrolasin; a ketone: 4-ethoxycyclohexanone; a phenol: 3,5-di-tert-butylphenol], which were not present in roots of other treatments, appeared as specific to TRIC8 treatment. Our study suggests that these metabolites might be involved in enhancement of hypocotyl length and in protection of sunflower against P. halstedii.

KEYWORDS:

• Downy mildew
• Helianthus annuus L
• Plasmopara halstedii
• root metabolites
• Trichoderma harzianum

Acknowledgement

We thank May Seed Company (Turkey) for kindly providing the sensitive cultivar ‘Sirena’ and pathotype 771 of Plasmopara halstedii. We are also grateful to Martha Rowe (University of Nebraska-Lincoln) and anonymous reviewers of our manuscript for improving the language and for useful remarks.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.