First Report on Natural Occurrence of Tomato Spotted Wilt Tospovirus in Basil (Ocimum basilicum).

Virus-like symptoms were observed on basil plants (Ocimum basilicum L. 'Mrs. Burns Lemon' [MBL]) growing in containers and a demonstration plot at the Louisiana State University Burden Research Plantation, Baton Rouge, during July 1998. Symptoms consisted of ring spots, leaf distortion, and severe mosaic. Mechanical transmission of the suspect virus by sap inoculation from infected MBL to basil cvs. MBL, Aussie Sweet, Cinnamon, Siam Queen, and Sweet Dani was successful. Symptoms were similar to those on infected MBL. Nicotiana benthamiana Domin. reacted with local chlorotic spots followed by severe yellows, necrosis, and death. Electron microscopy of thin sections of infected basil revealed virus inclusions but no virus particles. However, infected N. benthamiana revealed the presence of 82-nm membrane-bound particles in the cytoplasm. The virus was identified from basil and N. benthamiana as the common strain of tomato spotted wilt tospovirus (TSWV) by enzyme-linked immunosorbent assay (Agdia, Elkhart, IN). An outbreak of thrips insects during the summer drought in 1998 was probably responsible for the occurrence of TSWV in basil. This is the first report of the occurrence of TSWV in basil (1). Reference: (1) A. A. Brunt et al., eds. 1996. Plant Viruses Online: Descriptions and Lists from the VIDE Database. Published online by Australian National University, Canberra.