Selection of amitrole tolerant tobacco calli and the expression of this tolerance in regenerated plants and progeny.

Thirty-one clones capable of growth in the presence of 1.9×10(-4) M amitrole (3-amino-1,2,4-triazole) were isolated from non-mutagenized cell suspensions of haploid Nicotiana tabacum cv. 'Wisconsin 38' plants at a frequency of 2.5×10(-8). Seven clones retained tolerance when grown on selective medium for three years. When clones were cultured in the absence of amitrole, tolerance persisted for 9 months in five clones. Some plants regenerated from three amitrole-tolerant clones were tolerant. Seven amitrole-tolerant clones were isolated from diploid N. tabacum cell suspensions and R plant tolerance was followed through two sexual generations. Simple Mendelian inheritance patterns were not observed.