Virescence disease of Black cumin in Semirum region of Isfahan

Virescence disease of black cumin (Nigella sativa L.) was found in Semirom region in 2001. The major symptoms of the disease includes proliferation of auxiliary buds from the main stem, virescence, phyllody, development of ovary into a thickened enlarged and sac-like body, floral proliferation, small and chlorotic leaves, witche's broom and sever stunting. Light microscopy of hand-cut section of black cumin stem treated with diene's stain, revealed presence of regularly spaced dark blue areas in the phloem region of the infected plants. Phyllody agent was transmitted from infected black cumin to healthy black cumin by grafting and the leafhopper, Circulifer haematoceps in greenhouse. The mean rate of infection in spring and summer cultivations were estimated as 14 and 20.7 Percent respectively. Population density of leafhopper C. haematoceps in spring and summer cultivation were 3.6 and 18.5 adults per 100 net respectively. On the basis of disease symptoms, graft and leafhopper transmission and positive reaction with dienes, stain, black cumin phyllody in Semirom has phytoplasmal etiology. This is the first report of black cumin phyllody in Iran.