Short-duration colchicine treatment for in vitro chromosome doubling during ovule culture of Beta vulgaris L

Colchicine uptake into ovules of sugar beet after 7 days of culture and its chromosome-doubling effect on ovule-derived plants were studied with high colchicine concentrations (0.4-6.0%) and short treatment duration (0-5 h). The best result of 4.2 diploid plants per 100 ovules was produced by treatment with 0.4% colchicine for 2.5 h. Both colchicine concentration and treatment time of ovules showed toxic effects on embryo formation, but it was stabilized at a low level with short exposure. The chromosome-doubling effect, by contrast, was unchanged with the colchicine concentrations used, but highly affected by the duration of exposure studied. A maximum percentage of 60% diploid plants was obtained after 3-5 h of uptake, which corresponds to only 31-39% of the total capacity for colchicine uptake in the ovules. Further uptake of the drug produced mainly toxic effects. Flow-cytometric measurements of the ploidy level in plantlets in vitro and of the same plants before flowering in soil were similar in about 80% of cases. Thus, flow-cytometric selection of diploid plants in vitro may be an efficient tool.