ANTIMICROTUBULE HERBICIDES FOR IN-VITRO CHROMOSOME DOUBLING IN BETA-VULGARIS L OVULE CULTURE

In vitro chromosome doubling during ovule culture of sugar and fodder beets (Beta vulgaris L.) was studied with four anti-microtubule herbic ides: amiprophos-methyl (APM), oryzalin, pronamide, and trifluralin at concentrations of 0-300 mu M. Best chromosome doubling results were o btained by treatment of the ovules with 100 mu M APM which produced 4. 7 diploid plants per 100 ovules. Highest chromosome doubling was found with oryzalin using 1 mu M, with trifluralin at 10 mu M, and with pro namide at 10 mu M producing 2.8, 2.0, and 2.0 diploid plants per 100 o vules, respectively. The APM treatments showed relatively low toxicity on embryo formation which in combination with a high chromosome doubl ing effect, resulted in up to 89 diploids per 100 plants regenerated. Oryzalin and trifluralin had more severe toxic effects, which reduced embryo formation, thereby lower percentages of chromosome doubled plan ts were obtained from these treatments. Pronamide had no significant t oxic effect but it induced chromosome doubling at lower frequencies. C ompared to colchicine, APM seems to be as efficient for chromosome dou bting during beet ovule culture, but at molar concentrations 100 times lower than those used for chromosome doubling with colchicine.