Effect of colchicine induced tetraploids of ginger (Zingiber officinale Rosc.) on cytology, rhizome morphology, and essential oil content

Abstract

Ginger (Zingiber officinale Roscoe; 2 n = 22) is an important spice crop recognized for its medicinal benefits and pharmacological activities. The crop is said to have a narrow genetic base in the cultivated gene pool due to hinderance in sexual recombination. Polyploid induction is an efficient strategy to develop new cultivars in vegetatively propagated horticultural crops. In this study, successful induction of tetraploids (2 n = 44) in ginger ‘IISR Rejatha’ was achieved through colchicine treatment and the tetraploid plants were subsequently characterized. The 21 putative polyploids were identified by altered morphology, particularly plant height, leaf size, pseudostem height and thickness through colchicine treatment. The chromosome counts confirmed polyploidization in two of the tetraploid lines (2 n = 4x = 44), while that of the control diploid plants was 2 n = 2x = 22. Further, the ploidy levels of diploid and tetraploids were confirmed by flow cytometric analysis. The morphological characterization of the induced tetraploids revealed significant differences in leaf and pseudostem characters. Significantly larger rhizome diameter (3.26 cm) and higher yield per plant (418.65 g/plant) was recorded in Tetraploid 2 compared with Tetraploid 1 (2.88 cm, 320.81 g/plant) and diploid (2.00 cm, 280.33 g/ plant). Overall, the colchicine induced tetraploids in ginger have larger rhizomes and greater source of essential oil.