Use of amino acid analogue-resistant cell lines for selection of Nicotiana sylvestris somatic cell hybrids.

Nicotiana sylvestris cell lines resistant to the amino acid analogues S-2-aminoethyl-cysteine (AEC(R)), or 5-methyl-tryptophan (5MT(R)), were isolated in suspension culture. Assuming these resistances to be dominant, we have attempted to determine if such variant cell lines can be used to select double resistant somatic cell hybrids. A total of 1.8 × 10(4) control calli from mixed AEC(R) and 5MT(R) protoplasts, and AEC(R) and 5MT(R) homokaryotic fusions were placed on double analogue selection, but none survived. Eight somatic hybrid calli (0.8%), able to grow without inhibition on the double analogue selection medium, were obtained after AEC(R) + 5MT(R) protoplast fusion. These were further determined as hybrids on the basis of resistance level, chromosome number, and chlorophyll content, all characteristics differing in the parental cell lines.