Received: 30-08-2023 / Accepted: 05-01-2024
The study was conducted to isolate and identify the causal agent of leaf spot disease on cabbage (Brassica oleracea L. var. capitata) in Hung Tien, Nam Dan, Nghe An province. Ten symptomatic cabbage leaves were collected from three diseased fields. Morphological examination revealed that only one type of fungus (designated as BC01) was isolated from the cut surface of the diseased leaf pieces. The isolate BC01 had dark olive colonies, white margin, cottony mycelium, branched conidial chains, brown oval or ellipse conidia shape with a short cone-shaped beak at the head, 0-3 longitudinal septa and 1-5 transverse septa. The conidial size ranged from 10.17 to 40.06 × 4.16 to 13.09µm. Based on the ITS gene sequence analysis and morphological characteristics, the isolate BC01 was identified as Alternaria alternata. After 7 days of re-infection, the symptoms on the re-infection leaves were similar to those on the isolated leaves. At the site of infection, the fungal mycelium grew densely and invaded deep into the leaf tissue, while the control leaves showed no symptoms.