Effect of Alkylating Mutagens on Rooting Response and Callus Age on Shoot Regeneration of Rough Lemon (Citrus Jambhiri Lush.)

Many species of Citrus and compatible sexual relatives are being used to develop biotic and abiotic tolerant rootstocks and their ability to confer positive stionic effects. Citrus jambhiri is the commercial citrus rootstock in India, deep-rooted well adapted to the diverse agro-climatic conditions. It ensures high yield with large size fruits in most of the scion cultivars and at the same time is resistant to most of the viruses. For in vitro mutagenesis, leaf and epicotyl calli derived shoots were used as explant material. In-vitro mutagenesis is a valuable tool for improvement of a crop, especially when there is a need to add one or two easily identifiable characters in an otherwise well adapted variety, without disturbing its basic genotype. The alkylating agent methyl methane sulphonate (MMS) and ethyl methane sulphonate (EMS) at 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6%, were used for mutagenesis. The mutagenic calli derived shoots were regenerated on MS medium augmented with BAP (3.0 mg/l), followed by rooting in MS medium containing NAA (2.0 mg/l). Percent rooting (29.50-8.33%), (27.11-07.72%), number of roots per shoot (3.11-1.18), (3.12-1.04) and root length (4.13-2.22), (4.15-2.17) decreased with increasing doses of MMS and EMS treatments, respectively. Effect of increasing age of callus showed that callus retained regeneration capacity (3.55%) even after 210 days of culture by repeated sub-culturing. The plantlets were successfully acclimatized in different potting mixtures and highest survival rate (90.35%) was achieved in potting mixture containing garden soil with sand and farmyard manure (1:1:1).