Plant Cell Reports (2001) 20 : 16–21 Q Springer-Verlag 2001 Communicated by D. Dudits Á. Tantos 7 A. Mésáros 7 J. Szalai Department of Plant Molecular Biology, Faculty of Horticultural Science, Szent István University, Budapest, Hungary G. Horváth (Y) Department of Plant Molecular Biology, Faculty of Horticultural Science, Szent István University and Plant Physiology Research Group, Hungarian Academy of Sciences, P.O. Box 53, Budapest, Hungary, 1518 e-mail: ghorvath6omega.kee.hu Fax: c136-1-2096388 T. Farkas Institute of Biochemistry, Biological Research Center, P.O. Box 521, Szeged, Hungary, 6701 CELL BIOLOGY AND MORPHOGENESIS Á. Tantos 7 A. Mészáros 7 T. Farkas 7 J. Szalai G. Horváth Triacontanol-supported micropropagation of woody plants Received: 29 March 2000 / Revision received: 1 September 2000 / Accepted: 4 September 2000 Abstract The effectiveness of triacontanol in the micropropagation of two woody, economically impor- tant fruit plant species was investigated. Triacontanol was added to the routine multiplication and rooting media of apple (Malus domestica cv. JTE-E4) and sour cherry (Cerasus fruticosa cv. Probocskai) rootstocks at concentrations of 2, 5, 10 and 20 mg/l. It was found to increase the number of shoots and the fresh weight of apple in the multiplication phase and to enhance root number and chlorophyll content in the rooting phase. The addition of indole-3-butyric acid (IBA) to the media further improved the effect of triacontanol. A less pronounced effect could be seen in the multiplica- tion phase of sour cherry, although there was an enhancement of shoot proliferation. In the rooting phase, however, the application of triacontanol caused a significant increase in the number of roots per plant, and this effect was further improved when triacontanol was combined with 0.5 mg indole-3-butyric acid/l. Keywords Triacontanol 7 Apple 7 Sour cherry 7 Micropropagation 7 Growth regulator Abbreviations 2ABA 6-Benzylaminopurine 7 IBA Indole-3-butyric acid 7 MS Murashige and Skoog (1962) 7 PGR Plant growth regulator Introduction The micropropagation of woody plants is often proble- matic because of genotypic variation in the regenera- tion responses and the process of aging. Shoot cultures are commonly used in the micropropagation of economically important woody plants, e.g. fruits (Skirvin 1986). Apple is usually propagated in the pres- ence of 0.5–2 mg BA /l with only few or no auxin-like PGRs. Cherry cultivars respond better to somewhat lower concentrations of BA when explants proliferate new shoots arising principally from axillary buds (Morini et al. 1991). Root induction takes place in either PGR-free or auxin-like PGR-containing media (George 1993). IBA is generally used for inducing the roots of woody plants. In most cases chronic auxin-like PGR treatments (a standard concentration in the medium during root induction) have been used, but acute treatments (a short period with a high concentra- tion, followed by PGR-free medium) has sometimes been found to be more successful (Kataeva and Butenko 1987). Triacontanol, a natural component of the epicuti- cular waxes (Chibnall et al. 1933; Crosby and Vlitos 1959) has been shown to increase the vegetative growth, chlorophyll content and dry weight of various plants when applied in field conditions (Ries 1985). It can also be considered to be a potentially active agent in tissue culture because it can be autoclaved in solu- tion. For a long time, however, only Yun and Kim (1986) and Ma et al. (1990) tested triacontanol in tissue cultures. In a recently published paper we reported that triacontanol has a definite effect in the micropropaga- tion of balm, Melissa officinalis L., both in the multipli- cation and the rooting phases (Tantos et al. 1999); it enhanced shoot growth, fresh weight, chlorophyll