ABSTRACT
Tobacco is referred to as Virginia tobacco or cultivated tobacco and originates from South America. Tobacco-dried leaves can be cured and used to produce cigarettes, cigars, snuff and for pesticides. The pathogen survives in the soil as oospores and chlamydospores. The primary infection is from the soil-borne fungal spores and the secondary spread is through sporangia and zoospores transmitted by wind and irrigation water. The disease affects tobacco plants at all growth stages of all types of tobacco, and symptoms vary with crop age and weather conditions. Pathogen affects the roots and basal stem of the tobacco plant. The fungus lives as a saprophyte on crop residues and is also present as dormant mycelium in soil, oospores and chlamydospores causing primary infection. In warm, moist soil, chlamydospores germinate and infect tobacco roots by germ tube or produce sporangium and produce 5-to-30 zoospores.
