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 herbicides: amiprophos-methyl (APM), oryzalin, pronamide, and trifluralin at concentrations of 0-300 mu M. Best chromosome doubling results were obtained 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 pronamide at 10 mu M producing 2.8, 2.0, and 2.0 diploid plants per 100 ovules, respectively. The APM treatments showed relatively low toxicity on embryo formation which in combination with a high chromosome doubling 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 plants were obtained from these treatments. Pronamide had no significant toxic effect but it induced chromosome doubling at lower frequencies. Compared to colchicine, APM seems to be as efficient for chromosome doubting during beet ovule culture, but at molar concentrations 100 times lower than those used for chromosome doubling with colchicine.