Caracterización morfológica y molecular de fitopatógenos causantes de pudrición del tallo en Nicotiana tabacum L.

Stem rot in Nicotiana tabacum L. represents a phytosanitary problem that affects the development and yield of the crop. The objective of this study was to isolate and identify the phytopathogens associated with this disease using morphological and molecular methods. Symptomatic stem samples were collected from the San Carlos Tobacco Company. Isolation was carried out using PDA medium (for fungi) and nutrient agar (for bacteria), followed by purification. Morphological characterization allowed observation of reproductive structures such as microconidia, macroconidia, and chlamydospores in the case of the fungus, as well as determination of Gram reaction and cell morphology in the bacteria. For molecular identification, the ITS region was amplified and sequenced for fungi, and the 16S rRNA gene for bacteria. The results revealed the presence of Fusarium oxysporum with 99.85% similarity and 100% identity (accession MN417196.1), and Enterobacter hormaechei with 99.80% similarity and 100% identity (accession CP017186.1). The accurate identification of these pathogens will allow the development of more effective and environmentally responsible phytosanitary management strategies.