Biocontrol Mechanisms of Trichoderma koningiopsis PSU3-2 against Postharvest Anthracnose of Chili Pepper.

On-Uma Ruangwong,Kitsada Pitija,Anurag Sunpapao,Chaninun Pornsuriya

doi:10.3390/jof7040276

Abstract

Several mechanisms are involved in the biological control of plant pathogens by the soil-borne Trichoderma spp. fungi. The aim of this study was to characterize a new strain of Trichoderma as a potential biological control agent to control the postharvest anthracnose of chili pepper caused by Colletotrichum gloeosporioides. A total of nine strains of Trichoderma spp. were screened for their antifungal activity using a dual culture assay against C. gloeosporioides. Trichoderma koningiopsis PSU3-2 was shown to be the most effective strain, with a percentage inhibition of 79.57%, which was significantly higher than that of other strains (p < 0.05). In the sealed plate method, T. koningiopsis PSU3-2 suppressed the growth of C. gloeosporioides by 38.33%. Solid-phase microextraction (SPME) was applied to trap volatiles emitted by T. koningiopsis PSU3-2, and the GC/MS profiling revealed the presence of antifungal compounds including azetidine, 2-phenylethanol, and ethyl hexadecanoate. The production of cell-wall-degrading enzymes (CWDEs) was assayed through cell-free culture filtrate (CF) of PSU3-2, and the enzyme activity of chitinase and β-1,3-glucanase was 0.06 and 0.23 U/mL, respectively, significantly higher than that in the control (p < 0.05). Scanning electron microscopy of the mycelium incubated in cell-free CF of T. koningiopsis PSU3-2 showed the abnormal shape of C. gloeosporioides hyphae. Application of T. koningiopsis PSU3-2 by the dipping method significantly reduced the lesion size (p < 0.05) after inoculation with C. gloeosporioides compared to the control, and there was no disease symptom development in T. koningiopsis PSU3-2-treated chili pepper. This study demonstrates that T. koningiopsis PSU3-2 is an effective antagonistic microorganism and a promising biocontrol agent against postharvest anthracnose of chili pepper, acting with multiple mechanisms.

Highlights

Rhizosphere soil has long been considered as the main source of isolation of useful beneficial microorganisms [1,2]
T. koningiopsis PSU3-2 was shown to be the most effective strain, with a percentage inhibition of 79.57%, statistically higher than that of other strains (p < 0.05) in this assay (Figure 1); the T. koningiopsis PSU3-2 strain was selected for further bioassays
T. koningiopsis PSU3-2 was shown to be the most effective strain, with a percentage inhibition of 79.57%, statistically higher than that of other4 of 10 strains (p < 0.05) in this assay (Figure 1); the T. koningiopsis PSU3-2 strain was selected for further bioassays

Summary

Introduction

Rhizosphere soil has long been considered as the main source of isolation of useful beneficial microorganisms [1,2]. Trichoderma species are widely used to control numerous plant pathogens and reduce disease severity [3,4], due to their capacity for nutrient and space competition [5,6], parasitism [7], secretion of antimicrobial metabolites [7,8,9,10], activation of defense responses [11,12], and promotion of plant growth [8,9,13]. Application of the Trichoderma species has been used to reduce the disease severity of leaf spots on lettuce [12] and sugar beet [15], as well as brown spots on rice [16].

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