EFFECTS OF THE AMINO-ACID ANALOG, 5-METHYLTRYPTOPHAN ON PROTOPLAST SURVIVAL, PLATING EFFICIENCY AND FREE-TRYPTOPHAN LEVELS IN TUBERS OF REGENERATED POTATO PLANTS

In an attempt to improve nutritional qualities of the potato by exploi ting variation associated with protoplast regeneration, Russet Burbank leaf protoplasts were cultured in cell layer (CL) medium containing t he amino acid analog, 5-methyltryptophan (5-MT) at concentrations from 0 to 286 muM. At three day intervals, numbers of viable cells and div iding colonies were recorded to determine effects of 5-MT concentratio n on cell viability during the 14 day incubation period. Repeated coun t data were used in a computer program to construct survival profiles. Decline in cell populations was generally slight during the first 5 d ays in culture. Between day 5 and 11, survival rate dropped dramatical ly, averaging 10-12% per day regardless of concentration. As surviving cells began to divide, a leveling trend in the curves was noted betwe en days 11 and 14. Reduced plating efficiency was only associated with the 103 and 286 muM treatments. No plants were regenerated from colon ies exposed to 5-MT concentrations in CL greater than 34.4 muM nor wer e differences in free tryptophan found between tubers of protoclones a nd Russet Burbank.