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 an d its chromosome-doubling effect on ovule-derived plants were studied with high colchicine concentrations (0.4-6.0%) and short treatment dur ation (0-5 h). The best result of 4.2 diploid plants per 100 ovules wa s produced by treatment with 0.4% colchicine for 2.5 h. Both colchicin e concentration and treatment time of ovules showed toxic effects on e mbryo formation, but it was stabilized at a low level with short expos ure. The chromosome-doubling effect, by contrast, was unchanged with t he colchicine concentrations used, but highly affected by the duration of exposure studied. A maximum percentage of 60% diploid plants was o btained 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 befor e flowering in soil were similar in about 80% of cases. Thus, flow-cyt ometric selection of diploid plants in vitro may be an efficient tool.