Selection of high nicotine-producing cell lines of tobacco callus by single-cell cloning

Single-cell clones of Nicotiana tabacum callus showed wide variation in the production of nicotine. An efficient screening of numerous clones was made possible by the adoption of the ‘cell squash method’ devised for estimating the approximate alkaloid content of a small piece of callus. From these clones, several cell lines with higher yield of nicotine (1.0–3.4% of dry wt) have been isolated by repeated clonal selection.