Plant Cell, Tissue and Organ Culture 66: 25–29, 2001. © 2001 Kluwer Academic Publishers. Printed in the Netherlands. 25 Effect of genotype, explant type and growth regulators on organogenesis in Morus alba B.S. Bhau ∗ & A.K. Wakhlu Plant Tissue Culture Laboratory, Department of Botany Jammu University, Jammu 180 006 Jammu & Kashmir, India ( ∗ requests for offprints; E-mail: bsbhau@teri.res.in) Received 27 June 2000; accepted in revised form 26 February 2001 Key words: auxin, cytokinin, genotype, mature explant, Morus, mulberry, organogenesis Abstract Plantlets of the mulberry (Morus alba L. vars. Chinese White, and Kokuso-27) were produced from callus cultures. For callus induction, leaf, internodal segments, and petiole explants of Chinese White, Kokuso-27 and Ichinose varieties were grown on MS basal medium fortified with 2,4-D and 6-benzylaminopurine (BA). Callogenesis was dependent on the nature of explant used, the genotype and growth regulators supplemented in the medium. Leaves were the best explant type used for callus induction. Best callogenesis was obtained on MS medium containing a combination of 1 mg l -1 2,4-D and 0.5 mg l -1 BA (95-100%). Calluses formed shoots on MS medium sup- plemented with 1 mg l -1 BA. Supplementation with 0.1 mg l -1 2,3,5-triiodobenzoic acid (TIBA) in this medium enhanced shooting response. Presence of TIBA in the medium also improved the long-term organogenic potential of the callus. Regenerated shoots produced roots on Murashige & Skoog (MS) medium containing either 0.5 mg l -1 indole-3-butyric acid (IBA) or α-naphthaleneacetic acid (NAA). Seventy percent of the rooted plants were established in the field where they are performing well. Abbreviations: 2,4-D – 2,4-dichlorophenoxyacetic acid; BA – 6-benzylaminopurine; IAA – indole-3-acetic acid; NAA – ∝-napthaleneacetic acid; IBA – indole-3-butyric acid; MS – Murashige & Skoog; TIBA – 2,3,5-triiodobenzoic acid Introduction Mulberry (Morus) is an invaluable tree for the sericul- ture industry, as it is the only source of food for silk- worm (Wakhlu and Bhau, 2000). Morus alba L. vars. Chinese White, Kokuso-27 and Ichinose are promising genotypes for sericulture industry in temperate regions of the world. In India, these varieties are cultiv- ated for commercial purposes in Jammu and Kashmir, West Bengal, Karnataka and Tamil Nadu (Dandin and Sengupta, 1988; Rajan et al., 1992). Methods of con- ventional vegetative propagation through grafting is not economically viable for these varieties because it involves skilled manpower, expensive nursery facilit- ies and a minimum time period of 4–5 years to obtain plants ready for harvest (Bhau, 1999). Propagation of plants through cuttings is also not viable for these vari- eties due to their poor rooting ability. An attempt to induce rooting in stem cuttings of these varieties by auxin application has not yielded encouraging results (Fotadar et al., 1990). Tissue culture propagation can be a viable alternative for rapid multiplication of the mulberries. The successful regeneration of plants in vitro has been achieved in several mulberry species by axillary shoot proliferation and organogenesis from callus cultures (see review Wakhlu and Bhau, 2000). These studies have revealed that regeneration ability in Morus spp. is greatly dependent on the growth regu- lator combinations, explant type and the mulberry gen- otype (Jain and Datta, 1992; Kathiravan et al., 1995; Sahoo et al., 1997; Vijayan et. al., 1998). These factors have been investigated separately without examining their interaction and the regeneration potential of these protocols was very low and inconsistent (Jain and