Induction of adventitious shoots and tetraploids in Antirrhinum majus L. by treatment of antimitotic agents in vitro without plant growth regulators

We examined the effects of five antimitotic agents using Antirrhinum majus L. ‘Maryland True Pink’ on the induction of adventitious shoots resulted in increase of frequencies of chromosome doubling without plant growth regulators. Seeds were treated in vitro with 0, 16.5, 32.9, 65.8, 131.6, or 263.2 µM oryzalin (ORY), amiprofos-methyl (APM), butamifos (BUT), or propham (IPC) or 800, 1,600, 3,200, 6,400, or 12,800 µM colchicine (COL) for 7 day. ORY, COL and APM promoted induction of adventitious shoots on the hypocotyls at maximum frequencies of 57.6% with 16.5 µM ORY, 5.6% with 800 µM COL and 88.8% with 131.6 µM APM. ORY and COL also induced adventitious shoots on the epicotyls adjacent to the cotyledons, particularly at high concentrations, with a maximum frequency of 26.0% at 12,800 µM COL. APM treatment increased frequencies of tetraploids from 0.0 to 93.1%, with a positive correlation between the frequency and concentration. By contrast, ORY and COL induced tetraploids at frequencies of 16.0 to 54.6% and 4.0 to 59.4%, respectively, with peaks at both low and high concentrations of each. Correlation analysis revealed that frequencies of adventitious shoot formation could be useful as an index for the induction of tetraploids. These results showed that three of the antimitotic agents tested induced both adventitious shoot and tetraploid without plant growth regulators, indicating that antimitotic action may play a common role in the induction of adventitious shoot.