Reports of the increasing prevalence of black root rot in the areas where dark tobacco types are grown has triggered an accelerated effort from the tobacco research staff to develop and release additional varieties with high resistance to this disease. The high level of resistance to black root rot found in Nicotiana debneyi (an Australian species) is being used as the source of resistance in the breeding program.
Collins, Glenn B.; Legg, Paul D.; and Litton, C. C., "Control of Black Root Rot in Dark Tobacco" (1968). Agronomy Notes. 185.