## 4 Discussion
These metabolites play a crucial role in several key adaptive processes associated with ecological interactions and stress responses within their environment and are not directly associated with the growth or reproduction of fungi [167; 168; 169; 164], being often linked to communication and the defense of and/or attacks against their surrounding organisms or hosts [51]. Therefore, they are expected to be present in higher quantities in endophytes and phytopathogens, as presented in this study. Many secondary metabolites act as pathogenicity factors and have detrimental impacts on host health [163], largely due to the production of mycotoxins--toxic secondary metabolites encoded by BGCs. Mycotoxins can act as virulence factors, weakening or killing host plants and aiding colonization [170; 171; 172]. The _Nectriaceae_ fungi have been noted for their biological activity; for their parasitism on plants, fungi, and insects; and as producers of antibiotics and/or mycotoxins [173]. However, not much research has been conducted in the study of the mycotoxins of the genus _Neonectria_ during plant infection. Non-ribosomal peptide synthetases (NRPS) and polyketide synthases (PKS) are two types of large, modular enzyme complexes (megasynthases) involved in the biosynthesis of non-ribosomal peptides and polyketides, respectively. NRPS create molecules by joining amino acids. In contrast, PKS create molecules by joining acyl groups to form large polypeptide chains, which are responsible for many different catalytic domains, each performing a different chemical reaction. This allows them to create highly complex and diverse molecules [51]. In plant-associated fungi, NRPS and PKS have distinct functions in the synthesis of phytotoxins, mycotoxins, and antibiotics [174]. According to [PERSON] (2001) [175], numerous virulence factors have been identified in NRPS clusters, demonstrating them as necessary mechanisms in fungal pathogenesis. They were found in higher concentrations in plant pathogens and endophytes in this study and in lower amounts in freshwater saprobs. Terpene cyclases are enzymes found in plants and microorganisms that help to form monoterpenes, sesquiterpenes, and diterpenes by converting prenyl diphosphate chains. Terpenoids come from isopentenyl diphosphate (IPP), which prenyl transferases modify to create geranyl diphosphate (GPP), farnesyl diphosphate (FPP), and geranyl diphosphate (GGPP). These compounds serve as starting points for the production of monoterpenes (from GPP), sesquiterpenes (from FPP), and diterpenes (from GGPP) with the help of terpene cyclase enzymes [176; 177; 178]. Currently, over 80,000 terpenids are known [179]. Our study found the highest number of terpene clusters in plant-pathogenic fungi. The terpene is known in pathogenic fungi for producing many mycotoxins of the class sesquiterpenoids, which play a vital role in fungal virulence [180]. Terpenes can also have effects on fungal growth and protective effects against oxidative stress and UV radiation via the production of carotenoids [178; 181; 182]. Different environmental factors, including light and temperature, have been shown to change the production levels and compositions of carotenoids [183]. Ribosomally synthesized and post-translationally modified peptides (RiPPs) were found without many variations in this study. Fungal RiPPs are an increasingly important group of natural products, known for their powerful biological activity and antimicrobial, antifungal, or antiviral properties, with many scientific applications [184]. They are produced through a straightforward process. The initial step involves the synthesis of a precursor peptide by the ribosome, which consists of leader, core, and follower amino acid sequences. Subsequently, the core sequence undergoes specific post-translational modifications, guided by the leader and follower sequences. The final bioactive RiPP is released after these sequences are removed [185].