This strain of tobacco contained an unusually high amount of nicotine , nearly doubling its content from 3.2 - 3.5 % to 6.5 % .
In the 1970s , Brown & Williamson cross-bred a strain of tobacco to produce Y1 .
This strain of tobacco contained an unusually high amount of nicotine , nearly doubling strain 's content from 3.2 - 3.5 % to 6.5 % .
In the 1970s , Brown & Williamson cross-bred a strain of tobacco to produce Y1 .