## 1 Introduction  
Synthetic chemicals, such as fertilizers, herbicides and pesticides, used in horticultural production systems and during postharvest processes are environmental pollutants and potentially harmful to humans and animals [1]. The excessive use of broad-spectrum synthetic fungicides can affect the microbiome of the rhizosphere, including symbiotic fungi and beneficial bacteria. These microorganisms interact with the plants, modifying and promoting the availability of nutrients in the soil, such as nitrogen fixation [2]. In addition, numerous studies have shown that there is the risk of selection of resistant strains of pathogens to synthetic fungicides [3]. The excessive use of synthetic chemicals in farming systems has led governmental and international institutions to limit their use and shift interest towards sustainable food and agriculture (FAO, 2020). A valid alternative to synthetic fungicides is the use of biocontrol agents and/or their metabolites. Currently, several biocontrol agents are recognized including bacterial, such as _Agrobacteriumium_, _Bacillus_, and _Pseudomonas_, and fungal, such as _Ampelomyces_, _Aspergillus_, _Candida_, _Coniothyrium_, _Glicodium_, _Pseudozyma_, _Streptomyces_, and _Trichoderma_, agents [4]. In particular, the _Trichoderma_ genus have ability to adapt and thrive in different environmental conditions. This genus proved effective in the sustainable management of crop diseases caused by fungi. _Trichoderma_ spp. are among the most frequently isolated soil inhabiting fungi and are common in the plant rhizosphere. These fungi are opportunistic, avirulent plant symbionts, and act as parasites and antagonists of many phytopathogenic fungi, thus protecting plants from disease [5]. The antagonistic properties of _Trichoderma_ spp. are based on the activation of indirect and direct mechanisms. The indirect mechanisms are competition for space and nutrients, promotion of growth, and induction of plant defenses, whereas the direct mechanisms are mycop Parasitism and production of active metabolites and lytic enzymes. These indirect and direct mechanisms can act synergistically and depending on species and strain [6]. An interesting feature of _Trichoderma_ spp. is the production of volatile and nonvolatile secondary metabolites capable of inhibiting the growth of pathogens. However, little is known about their production which can vary from strain to strain. Based on their structure, known metabolites with antibiotic activity can be classified into two main types: (i.) low-molecular-weight and volatile metabolites and (ii.) high-molecular-weight and polar metabolites. Low molecular weight and volatile metabolites include simple aromatic compounds, volatile terpen, and isocyanide, and relatively nonpolar substances with significant vapor pressure [7]. These \"volatile organic compounds\" in the soil environment would be expected to diffuse over a distance through systems thus enhancing the performance of the organism by affecting the physiology of competitor organisms [7; 8]. High-molecular-weight and polar metabolites, like peptaibols, may exert their activity through direct interactions between _Trichoderma_ species and their antagonists [7]. In this study, we tested the antagonistic ability and the production of secondary metabolites with inhibitory activity of strains of _Trichoderma asperellum_ and _Trichoderma atroviride_ on different pathogens of the genera _Fusarium_, _Aspergillus_, _Penicillium_, _Colletotrichum_, _Neofusicoccum_, and _Pltyophthora_, that cause loss to agricultural crops.