Nutritional and karyotypic characterization of a haploid cell culture ofDaucus carota

Summary The purpose of this study was to optimize growth conditions for a strain of haploid carrot callus and to follow its karyotypic changes in a long span of time. The strain has been maintained in liquid suspension since September 1977. It has remained predominantly haploid in its karyotype since that time. The original explant was initiated and subsequently subcultured in Gamborg's B5 medium. The components of the B5 medium were omitted one at a time and sequentially added back to determine their minimum, optimum, and maximum nontoxic concentrations. These changes were made in the original formula: the addition of an organic buffering agent and an increase in the iron and other micronutrient concentrations. Using this slightly modified B5 medium, we assessed the effect on growth by single additions of amino acids, different carbon sources, growth regulators, and vitamins. No improvement in plating efficiency resulted from addition of any of these compounds. We conclude that there are factors limiting the plating efficiency of the haploid cells other than these tested, or that single additions will not make a discernible difference, or that growth promoting factors cannot be exogenously supplemented to cultured cells.