Optimization of an efficient Agrobacterium mediated genetic transformation in chilli (Capsicum annuum)

Chilli (Capsicum annuum) is one of the important commercial spice crops in India and well known for its recalcitrant genetic nature. Due to its genetic nature, implicates the limitations in application of genetic engineering. Hence, the present study emphasized with optimization of effective Agrobacterium mediated transformation in major chilli cultivar of Tamil Nadu. The regeneration and transformation potential of chilli cultivar K2 and CO-4 was tested with explants of hypocotyl, leaf and cotyledon for different combinations of plant growth hormones. The maximum per cent calli induction was observed with hypocotyl (61.33%) followed by leaf (57.33%) and cotyledon (21.33%) explants of CO-4 variety. Indeed, K2 variety observed to be not responsive for regeneration as CO-4 and often showed the senescence reaction. The combination of cytokinin 2,4-D (5 mg l⁻¹) with auxin NAA (5 mg l⁻¹) was found to be highly effective in supporting regeneration of chilli. The hypocotyl explant produced amorphous calli at 25–30 days whereas shoot proliferation was observed at 40–43 days. On the other hand, leaf and cotyledon explants yielded calli induction at 30–35 days but failed to give shoot proliferation. There are 4–5 shoot buds were observed from the differentiated calli of inoculated hypocotyl explants. After 50–60 days of complete shoot proliferation, elongated shoots were separated and transferred for the root induction for 10–15 days. The presence of transgene in the putative lines was confirmed through molecular screening with NPTII, 35S promoter and replicase gene specific primers.