Exploring the Antifungal Potential of the Brown Macroalga Hormophysa triquetra: Morphological Disruptions and Structural Changes in Plant Pathogens.

Recently, macroalgal extracts have gained attention for their valuable biologically active metabolites, known for their antimicrobial activities. This study aimed at exploring the antifungal properties of the aqueous (AQ), ethanolic (ET), and methanol: chloroform (MCF) extracts of brown macroalga Hormophysa triquetra, collected from Ad-Dukhan, Qatar. The extracts were evaluated for antifungal potential against Fusarium species, Alternaria alternata, and Colletotrichum gloeosporioides, using the agar disc method. The results revealed that the AQ extract exhibited no inhibitory action against phytopathogens, whereas ET and MCF extracts demonstrated antifungal potential against Fusarium species and A. alternata. Although fungal radial growth was not inhibited by the application of the extracts, significant morphological variations were evident indicating fungistatic behaviour of extracts. Microscopic images of the fungi treated with extracts showed hyphal deformations, compaction, abnormal thickness, vacuolization, and presence of pseudo-hyphal morphotypes. SEM analysis further confirmed alterations in structure of the fungi treated with extracts as compared to controls. In vivo analysis on cucumber further validated the extract's ability to suppress fungal growth, with a disease incidence of 66.7% and disease severity of 37.8%. GC/MS of the extracts revealed the presence of different bioactive compounds, primarily fatty acids, in both ET and MCF extracts.