Genetic variability induced in Nicotiana sylvestris by protoplast culture

Plants were regenerated from axenic plantlets by mesophyll protoplast culture, without mutagenic treatment. Two different lines of Nicotiana sylvestris were used: an original line, and a diploid androgenetic line derived from it. The regenerated plants were either diploid and phenotypically similar to their respective protoplast source line, or tetraploid. Genetic studies carried out on several diploid regenerated plants revealed genetic variability. Eight of 13 selfed progenies of plants regenerated from the original line, and 1 of 8 selfed progenies of plants regenerated from the androgenetic line, produced new mutant phenotypes never observed in the protoplast source lines. Two plants regenerated from the same protoplast-derived callus produced different mutations. Selfed progenies without a recognizable mutant phenotype were also different from their respective protoplast source line for quantitative characters; protoplast culture induced a depressive effect on the size of plants derived from protoplasts at younger and older stages of development. The origin of this depression and of the mutations is discussed.