# Volatile Organic Compound from _Trichoderma asperelloides_ TSUI: Impact on Plant Pathogenic Fungi
## 1 Introduction  
Soil is an important source of beneficial microorganisms. Multiple soil fungi participate in the decomposition of organic matter to deliver plant nutrients [1]. They play an important role in plant protection against pathogens as biocontrol agents that influence soil health [2]. _Trichoderma_ is a genus of filamentous ascomycete fungi that are frequently isolated from soil or rhizosphere soil in tropical areas containing approximately \(10^{1}\)-\(10^{3}\) culturable propagules per gram [3, 4]. _Trichoderma_ is the most important genus of beneficialmicroorganisms in agricultural soil, and it has been widely used in crop-plant production [5]. It is used as a natural-decomposition agent [6], plant-growth promoter [7], and as a biocontrol agent of plant diseases [8; 9] and bioremediation [10].  
One of the most dominant abilities of _Trichoderma_ species is as a biocontrol agent against plant diseases. Several _Trichoderma_ strains were widely studied due to their capacity to compete for nutrients and space [11; 12], parasitize other fungi [13; 14], enact antibiosis by producing secondary metabolites or antimicrobial compounds [15; 16], induce defense responses in plants [17; 18], and promote plant growth [15; 19]. The key to the success of _Trichoderma_ species in the soil is their fast growth and high reproductive ability, aiding them in surviving under unfavorable conditions, and their ability to utilize nutrients and antagonize plant pathogenic fungi [20; 21].  
Producing volatile organic compounds (VOCs) is considered to be an effective antibiosis mechanism of _Trichoderma_ species. _Trichoderma_ species produce and emit valuable volatiles associated with antimicrobial ability, induce defense responses in plants, and promote plant growth [15; 16]. VOCs released by several species of microorganisms directly inhibit the growth of pathogens or cause abnormal changes of pathogens, resulting in the weakness of pathogens interacting with plant hosts [22; 23]. For instance, _T. spirale_ T76-1 was reported to produce VOCs to restrict the fungal growth of _Corynspora cassificola_ and _Curvalaria aeria_, the leaf-spot pathogens in lettuce [12]. [PERSON] et al. [24] also reported that _Trichoderma_ sp. T76-12/2 produces VOCs to inhibit the growth of _Sclerotium rolsii_.  
The capacity to produce beneficial compounds, especially the VOCs, by _Trichoderma_ species is particularly interesting. Some _Trichoderma_ strains produce valuable VOCs with multifaceted mechanisms involved in biological control, inducing defense responses and promoting plant growth [12; 15; 16]. The antifungal ability of VOCs released by _Trichoderma_ is highly interesting because effective VOCs can be applied as biofumigants in controlling plant diseases and pests. Therefore, the screening of novel volatile-producing _Trichoderma_ strains is still being conducted. As soil is the main source of beneficial microorganisms, this study characterizes the antifungal activity of VOCs released from _Trichoderma_ that were isolated from soil. The isolation of _Trichoderma_, the identification of _Trichoderma_ by morphology and molecular properties, and VOC bioassay against plant fungal pathogens were conducted.