Effect of various media on micropropagation of MM111 apple rootstock

The present study was carried out to examine the in vitro propagation of MM111 apple rootstock, using different thidiazuron (TDZ) (0.0-1.0 microM) and BA (0.M) concentrations as well as their combinations. Rooting of microshoots of MM111 using various IBA concentrations under dark vs. light; and liquid vs. solid media was evaluated. The preliminary experiment indicated that TDZ could be suitable for MM111 during the multiplication when used at concentrations ranged between 0.1-1.0 microM. During first subculture, all TDZ concentrations caused a significant increase in shoot fresh weight when compared to BA concentrations and the control; however, BA treatments gave a significant increase over the control in this respect. Results of the second subculture came in support of the first one. The highest shoot number was obtained at 0.40 microM BA. At higher BA (=2.64 microM) and TDZ (=0.6 microM) concentrations, average shoot length was reduced compared to the lower concentrations. The combined treatment 0.44 microM BA + 0.1 microM TDZ caused an increase in average shoot length over the control as well as over the other treatments. TDZ at low concentations caused a significant increase in callus production over the control and all BA concentrations. Results of the second culture came to support those of the first one. Vitrification increased significantly only at 0.2 microM TDZ, 0.44 microM BA + 0.1 TDZ and 0.88 microM BA + 0.2 microM TDZ over the control. In the second subculture, a significant increase in shoot over the control occurred at all BA (except at 0.88 and 1.76 microM BA) and all TDZ concentrations and their combination treatments. The control showed no significant difference in shoot legth from those grown on media containing 0.88 and 3.52 microM BA and 0.4, 0.6, 0.8 and 1.0 microM TDZ. All BA treatments did not cause vitrification, however, TDZ showed a trend towards increasing the number of vitrified shoots up to 0.8 microM TDZ; at 0.1 microM TDZ and 1.32 microM BA + 0.3 microM TDZ, a significant increase over the control was obtained. With respect to root number and average root length, the control only caused significant increase in both variables in both cultures. IBA interacted significantly with presence or absence of light, whereas the separate effect was insignificant; the highest rooting percentage was obtained at 2.5 microM under dark but it was not significantly different from those grown under light at any IBA concentration, and at 5.0 microM IBA under dark. Intermediate root number per MM111 apple microshoot was obtained at all IBA concentations when incubated under light, however, these IBA concentrations showed no significant differences from those grown in dark at any concentration. The shortest root length was obtained at 10.0 microM IBA when shoots were incubated in dark in comparison with those grown on a medium of 5.0 or 10.0 microM IBA icubated in dark or light, respectively. The solid medium was significantly superior to rooting percentage, root number and average root length as compared to the liquid medium supported by perlite