Organogenesis and plant regeneration in Zephyranthes rosea Lindl.: Histological and chromosomal study

Abstract

The genus Zephyranthes rosea is a member of the family Amaryllidaceae. The plant is widely cultivated as ornamental. The objective of this study was to optimize an in vitro propagation method for the production of genetically stable Z. rosea plant. The chromosomal status of the regenerated plants was also studied to determine their ploidy levels and to identify the structural and numerical variations, if any. Two explants of Zephyranthes rosea, i.e. bulb scale and flower bud (3–4 mm each), were used and incubated in a culture room at 25 ± 2°C in which two different types of calli were induced from two sources. The MS medium amended with 2,4-dichlorophenoxyacetic acid (2,4-D) (0.5–2.0 mg/l) successfully induced callus from bulb-scale explants (50.25–57.5%). The addition of coconut water (10%) in 2,4-D-added medium further improved the callus induction frequency (68.4%). Bulb-scale calli were found to be highly regenerative while flower-bud calli did not show any organogenetic responses. The use of plant growth regulators, such as naphthaleneacetic acid (NAA) + benzylaminopurine (BAP), was found to be very effective for shoot bud development; maximum shoot number (11.50/callus mass) was observed in NAA (0.5 mg/l) + BAP (1.0 mg/l) added medium. Histological analysis of callus revealed that the origin of the shoot bud was de novo. Rooting frequency (65.25%) and the number of roots (7.5/shoot) were best achieved in indole-3-butyric acid (4.0 mg/l)-amended medium, followed by indole-3-acetic acid (4.0 mg/l). The regenerated Z. rosea plants showed 2n = 24 chromosome numbers.