Molecular Identification and Phylogenetic Analysis of <em>Fusarium</em> spp. Associated with <em>Triticum aestivum</em> L. Based on DNA Barcoding of<em> β-tub </em>Gene

Fusarium spp. are active producers of mycotoxins that enter the food chain and pose risks to human health. Identifying pathogenic agents is a key step in developing disease management strategies. For the first time in Bulgaria, we identified Fusarium species in wheat, harvest 2024÷2025, through the application of DNA barcoding. For genetic marker and construction of phylogenetic tree, the protein-coding gene β-tub was chosen. Among 26 identified isolates, F. sporotrichioides (42.3%) dominated, followed by F. proliferatum 23.1%), F. avenaceum (7,7%), F. armeniacum (7.7%), аnd F. poae (7,7%). F. tricinctum (3.8%), F. oxisporum (3.8%), and F. equiaseti (3.9%) were weakly expressed. Phylogenetic analysis classified the isolates into 5 species complexes: FSAMSC, FFSC, FTSC, FIESC, and FOSC and highlighted the genetic distances between them.Molecular genetic analysis showed that 84.6% of the wheat samples contained only one species of Fusarium, and in 15.4% the co-presence of two species was established. The largest share was in samples with low infestation 2÷4%, which represented 35% (n=32) of all positives. No statistically significant difference was found between the varieties and the level of contamination, as well as between the origin of the selected varieties and the level of contamination.