Plantlet regeneration from long-term callus cultures of Citrus acida Roxb.and the uniformity of regenerated plants

Callus cultures were initiated from epicotyl explants of in vitro grown nuc ellar seedlings of Citrus acida. Best callus induction occurred on MS mediu m containing BAP and 2,4-D and when explants were incubated in the dark. Hi gh levels of MS vitamins enhanced callus initiation and growth. These calli could be maintained in culture for upto two years and plantlets regenerate d from them on transfer to light. Greening of callus and regeneration of sh oot-buds from callus occurred on transfer to MS media with BAP. These shoot s grew further in media with both, BAP and GA(3), Rooting of shoots occurre d on media with NAA or IBA and the rooted plantlets could be transferred to sail. Regeneration of shoots and roots decreased with increase in age of c allus. Cytological study of the regenerants revealed no change in chromosom e number. Thus, genetically uniform plantlets could be regenerated continuo usly from established callus upto two years old, thereby helping in multipl ication and conservation of the species. (C) 1999 Elsevier Science B.V. All rights reserved.