Chromosome doubling in vitro with amiprophos-methyl in Beta vulgaris ovule culture

Chromosome doubling in vitro of sugar beet (Beta vulgaris L.) ovules precultured for 0-10 days was studied with the antimicrotubule herbicide amiprophos-methyl (APM) in 20, 150, 300 muM concentrations and with 2, 5 or 18 h of treatment. Efficient chromosome-doubling results were obtained at 150 muM APM for 5 h, which produced 56-64% diploid regenerants from B. vulgaris ovule culture. APM was found to possess chromosome-doubling effects in combination with toxic effects on embryo formation. A clear positive chromosome-doubling effect was indicated with prolonged preculture of the ovules before the APM treatment. The percentage of diploid shoots increased from 31 to 56 when prolonging the preculture from 0 to 10 days. Surprisingly, a high formation of tetraploid shoots (10-25%) was, moreover, obtained from the APM studies.