ABSTRACT
The varietal background needs to be totally updated when the new m aterial exhibiting m orphological m arkers linked to low TH C-content is developed, m aking it possible to distinguish drug-free cultivars by visual inspection. This context includes the efforts to induce new m orphological m arkers concerning the leaves or the stem, easily detectable, linked to low or free content o f THC (Faeti, M andolino, and Ranalli, 1996; Grassi, M oschella, and Fiorilli, 1997; Ranalli et al., 1997). A breeding program based on a m utagenesis approach aim ed at this purpose is currently in progress in Italy (Ranalli et al., 1996; M andolino et a l , 1997; Zottini, M andolino, and Ranalli, 1997).
