Role of Volatiles from the Endophytic Fungus Trichoderma asperelloides PSU-P1 in Biocontrol Potential and in Promoting the Plant Growth of Arabidopsis thaliana.

Nongnat Phoka,Siwaret Arikit,Shin-Ichi Ito,Kenji Matsui,Saisamorn Lumyong,Anurag Sunpapao,Nakarin Suwannarach

doi:10.3390/jof6040341

Abstract

Fungal volatile organic compounds (VOCs) emitted by Trichoderma species interact with a plant host and display multifaceted mechanisms. In this study, we investigated the antifungal activity of VOCs emitted by Trichoderma asperelloides PSU-P1 against fungal pathogens, as well as the ability of VOCs to activate defense responses and to promote plant growth in Arabidopsis thaliana. The strain’s VOCs had remarkable antifungal activity against fungal pathogens, with an inhibition range of 15.92–84.95% in a volatile antifungal bioassay. The VOCs of T. asperelloides PSU-P1 promoted the plant growth of A. thaliana, thereby increasing the fresh weight, root length, and chlorophyll content in the VOC-treated A. thaliana relative to those of the control. High expression levels of the chitinase (CHI) and β-1,3-glucanase (GLU) genes were found in the VOC-treated A. thaliana by quantitative reverse transcription polymerase chain reaction (RT-PCR). The VOC-treated A. thaliana had higher defense-related enzyme (peroxidase (POD)) and cell wall-degrading enzyme (chitinase and β-1,3-glucanase) activity than in the control. The headspace VOCs produced by PSU-P1, trapped with solid phase microextraction, and tentatively identified by gas chromatography–mass spectrometry, included 2-methyl-1-butanol, 2-pentylfuran, acetic acid, and 6-pentyl-2H-pyran-2-one (6-PP). The results suggest that T. asperelloides PSU-P1 emits VOCs responsible for antifungal activity, for promoting plant growth, and for inducing defense responses in A. thaliana.

Highlights

Trichoderma species are widely considered potential biological control agents (BCAs) against several plant diseases due to their unique characteristics
We tested the antifungal abilities of commercial compounds on the fungal growth of plant pathogens (Table 4), and we found that 6-PP was the most effective volatile against the plant pathogens Ganoderma sp., P. oxalicum, S. rolfsii, and S. cucurbitacearum (Table 4)
Among the volatile organic compounds (VOCs) produced by Trichoderma species, 6-PP with a sweet coconut-like aroma was considered the most important produced by T. asperellum [4], T. viride [41], T. harzianum [42], T. koningii [43], and T. atroviride [44,45]

Summary

Introduction

Trichoderma species are widely considered potential biological control agents (BCAs) against several plant diseases due to their unique characteristics They can produce bioactive secondary metabolites [1], compete for nutrients and space [2,3], induce plant defensive mechanisms [2,4,5], and promote plant growth [6]. They feature mechanisms such as antibiosis by producing extracellular cell wall-degrading enzymes [3,7] and mycoparasitism [8] Such abilities allow to use Trichoderma species as BCAs in agriculture for controlling plant diseases and for promoting plant growth [9]. The combination of antibiosis, a widespread mechanism used by Trichoderma species, and the endophytic relationship plays an important role in defense against several pathogens by releasing metabolites that act as antifungal compounds [1]

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