Sweet basil (Ocimum basilicum L) is one of the most important vegetable crops in the family Lamiaceae, being employed mainly as a source of essential oils for the pharmaceutical industry. Samples of plants showing symptoms of wilt, stem blight and collar root rot were collected during the 2005 hot rainy season in the rural area of Brazlândia (Federal District) in central Brazil. Two other samples displaying identical symptoms were collected under greenhouse and field conditions in Ponte Alta (DF). The fungus Fusarium oxysporum was consistently isolated in all samples. Pathogenicity tests were conducted using seedlings and stem cuttings of the O. basilicum cultivars 'Dark Opal' and 'Italian Large Leaf' as well as accessions of the species O. americanum L, O. campechianum Mill., Origanum manjorana L., O. vulgare L., Mentha arvensis L., Coleus blumei Benth., Leonorus sibiricus L. and Leonotis nepetaefolia (L.) W.T. Aiton. All isolates were highly virulent on O. basilicum cultivars, whereas O. campechianum and O. americanum cultivars reacted with a slight vascular browning and with a very mild reduction in plant growth rate. All isolates were considered avirulent to O. manjorana, O. vulgaris, M. arvensis, C. blumei, L. sibiricus and L. nepetaefolia accessions. The experimental data indicated that the causal agent of this disease is the fungus F. oxysporum f. sp. basilici. This is the first formal report of this pathogen in Brazil. The remaining seeds from commercial lots that were sowed in the areas where the pathogen was first described were evaluated for the presence of F. oxysporum f. sp. basilici. This fungus was detected in four out of six seed lots and the seed-derived isolates were able to induce similar set of symptoms in the same group of plant accessions. This result strongly suggests that this new disease in Brazil was most likely introduced into the country via contaminated seeds.
Fusarium oxysporum f. sp. basilici; Ocimum basilicum; etiology; seed pathology