The identification of an appropriate selection condition typically requires careful dose response curves to determine the correct concentration of a toxin (for example, selections using herbicides, FuDR, etc.) that results in a sufficient inhibition of gametophyte growth or development. Several factors may need to be considered when choosing the appropriate selection regime, for example: The nature of the toxic response, e.g. whether abrupt or gradual The pattern of gametophytic growth and development over time, e.g. whether gametophytes exhibit differential response dependent upon age. Identification of phenotypes other than growth that may identify mutants Also for identification of putative morphological mutants (for example clumped chloroplast or callus-like growth habit) careful observation of gametophytes at a sufficiently young stage is important.

The standard selection procedure is outlined in this illustration.(Figure not yet available!)

An example of a successful selection using media supplemented with FuDR is illustrated below. There are about 12,000 spore on this dish and all except one are severly inhibited or killed by this concentration of FuDR. The single individual (right, central region of dish) exhibits tolerance to FuDR and has nearly normal growth and development.

(1) All listed selections, with the exception of 230X, were derived from the Hn-n strain. Strain designations ending with 'n' indicate that a number of independent selections are available, all of which have not been fully characterized genetically.