New aromatic cytokinins can make the difference

A number of derivatives of the cytokinin 6-(3-hydroxybenzylamino)purine (meta-topolin, mT) was evaluated in the micropropagation system of Petunia hybrida or Rosa hybrida: 6-(3-methoxybenzylamino)purine (meta-methoxytopulin, MemT), 6(3-methoxybenzylamino)purine-9-riboside (MemTR), 6-(3-fluorobenzylamino)purine (FmT) and 6-(3-fluorobenzylamino)purine-9-riboside (FmTR). A leaf-variegated petunia chimera with a green-white-green (GWG) histogenic composition was used as a model plant to evaluate meristem stability during micropropagation. MemTR was superior to BA regarding a reliable multiplication of this chimera. In contrast with MemTR, BA induced too much non-variegated shoots. Roses that are micropropagated with BA, suffer from early senescence in vitro. From 4-6 weeks on, some leaves and shoots deteriorate and gradually all the plants in the jars die. The compounds FmT and FmTR showed the best shoot multiplication rate but MemTR had the best anti-senescing effects. After 18 weeks, only half of the plants on MemTR was completely brown. For BA, mT, MemT, MemTR, FmT and FmTR, this was respectively 85, 67, 67, 93 and 76%.