Effects of Cytokinin on Multiplication and Rooting of Aloe barbadensis during Micropropagation on Agar and Liquid Medium

Aloe barbadensis (syn. Aloe vera) was micropropagated on agar and liquid medium at varied benzyladenine (BA) and meta-topolin (MT) concentrations(0, 1, 3.2, and 10 μM) for three successive culture cycles and then transferred to a greenhouse for growth. MT induced multiplication at the highest concentration (10 μM) and BA produced the greatest number of plantlets (at 3.2 μM) with optimal multiplication at approximately 6 μM. Liquid medium did not affect multiplication rate when compared with agar, but plants were twice as large fromliquid as compared with those from agar at the time of transfer to the greenhouse. After five weeks of growth, plants in the greenhouse icropropagated on liquid culture were still larger than plants micropropagated on agar with BA and MT. A carryover of cytokinin inhibited rooting, and plants on agar were more severely affected than plants on the liquid medium. Cytokinin carryover reduced rooting from 92% (control) to 68% with either the 3.2 μM MT or 10 μM BA and at 10 μM MT only about 20% of the aloe plants rooted. There appeared to be a trade-off between maximum multiplication rates and best plant quality for ex vitro transfer. Using liquid medium led to larger plants and lessened the cytokinin carryover effect on rooting without affecting the multiplication rate. Approximately 6 μM BA in liquid medium would be optimal for multiplication and rooting of A.barbadensis