Morphological and Molecular Identification of Fusarium Oxysporum as the Main Cause of Wilt Disease of Tomatoes Grown in Greenhouses in Albania

When growing tomatoes indoors, Albanian farmers face plant diseases caused by the endophytic fungus Fusarium oxysporum. This causes significant losses to farms and reduces their export potential. The study aims to review the methods for identifying this pathogen and assess its prevalence, as well as the feasibility and conditions for using nucleotide sequence analysis in its identification. Damaged root and shoot tissues from 50 plants with signs of the disease were collected in the regions where tomatoes are most widely grown. The samples were surface sterilised and placed on potato dextrose agar (PDA). Incubation was carried out at 25°C for 7-10 days. Next, individual target colonies were isolated, and their cultural and morphological identification was performed, supported by light microscopy using an immersion objective. The colour, shape and texture of the colonies, their growth dynamics, time of emergence and sporulation intensity were considered. For the strains selected in this way, the nucleotide sequence was determined by polymerase chain reaction and compared with those in the GenBank database of the National Centre for Biotechnology Information using BLASTn search. As a result, it was determined that all affected plants contained strains of Fusarium oxysporum. At the same time, the use of nucleotide sequence analysis revealed inaccuracies in the preliminary identification by traditional methods. Thus, the expediency of additional measures for strain identification was determined, when conducting research for which high species specificity is critical. It was also found that farmers in Albania need to take measures to identify the strains of this fungus in plant tissues and soil on which they are grown.