EVALUATION OF ALTERNATIVE NITROGEN AND CARBON-SOURCES FOR SUGAR-BEET SUSPENSION-CULTURE PLATINGS IN DEVELOPMENT OF CELL SELECTION SCHEMES

Low molecular weight nitrogenous impurity compounds as well as raffino se are negative quality factors that interfere with efficient processi ng of sugarbeet (Beta vulgaris L.) for sucrose. In order to identify n utrient media for cell selection of biochemical mutants or transgenics that might have reduced levels of these processing impurities. the ab ility of 10 endogenous compounds to serve as sole nitrogen or carbon s ource for suspension plating and subculture callus growth was evaluate d. The most productive concentrations of nitrate, ammonium, L-glutamin e, L-glutamate, urea, and L-proline as sole nitrogen sources supported plating callus growth at 106, 159, 233, 167, 80, and 52%, respectivel y,, as well as the historical 60 mM mix of nitrate and ammonium in Mur ashige-Skoog medium. Glycine betaine and choline did not support growt h. D(+) Raffinose and D(+) galactose supported plating callus growth o nly 67 and 25%, respectively, as well as sucrose as sole carbohydrate source. No callus growth occurred on glutamine, glutamate, or glycine betaine as the sole carbon or carbon plus nitrogen source. Platings on either nitrate or ammonium as sole nitrogen source did not differ in sensitivity to the nitrate uptake inhibitor phenylglyoxal, suggesting that phenylglyoxal lacks the specificity for use in selection for muta nts of nitrate uptake. The ability of raffinose to be used as the carb on source, and glutamine or glutamate as the nitrogen source, may prec lude their use for selection of genetic variants accumulating less of these processing impurities. However, mutants or transgenics able to u tilize either glutamine, glutamate, or glycine betaine might be select able on media containing any one of these as carbon, nitrogen, or carb on plus nitrogen source, respectively, that is incapable of supporting wild-type cell growth.