One of the basic prerequisites for any tissue culture system is the establishment of efficient callus initiation and subsequent plantlet regeneration. Callus cultures were established from seedling roots and immature glumes on Linsmaier and Skoog (LS) and Murashige and Skoog (MS) media. In the present study, 2,4-dichlorophenoxy acetic acid (2,4-D) and its analogues such as 2,4-5 trichlorophenoxy acetic acid (2,4-5T) and 2(2,4-5 trichlorophenoxy) propionic acid (2,4-5P) were used in concentrations ranging from 0.5 - 4 mg/I for callus induction and maintenance of cultures. Callus growth was assessed by fresh and dry weight analysis after four weeks (See Table). The results indicate that low levels of 2,4-5T and 2,4-5P were superior over 2,4-D for callus initiation from root cultures whereas 2,4-D is the auxin requirement for glume explants. Multiple roots were observed in medium with low levels of 2,4-D, 2,4-5T and 2,4-5P. The differential optimal requirement of auxins for callus induction in roots and glumes may be due to physiological status of the explants and that auxin sites may have a higher affinity for analogues than 2,4-D (Sanchez et al., Ann. Appl. Biol. 98:347-353, 1981). Suspension cultures were also obtained from the above callus cultures in liquid medium. Further studies of plating of cells or cell aggregates and regeneration of roots and shoots are in progress.
P. Suprasanna, K. V. Rao and G. M. Reddy
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