Embryogenesis followed by enhanced micro-multiplication and eco-restoration of Calamus thwaitesii Becc.: an economic non-wood forest produce for strengthening agroforestry system

Abstract

The present study is focussed on development of a high-frequency micro-multiplication system in Calamus thwaitesii, through somatic embryogenesis from immature zygotic embryos cultured in Murashige and Skoog (MS) medium supplemented with 31.68 µM 2,4-dichlorophenoxyacetic acid (2,4-D). The semi-friable calli when cultured in the same medium augmented with 2.22 µM 6-benzylaminopurine (BAP) and 1.07 µM α-naphthalene acetic acid (NAA) induced ~ 12 discrete globular embryoids in 6 weeks. The isolated embryoids in hormone-free media yielded 65% plantlets. Furthermore, embryoids and axenic shoots exhibited maximum shoot induction in medium supplemented with 0.45 µM Thidiazuron (TDZ). The shoot initials after subculture in media supplemented with 1.78 µM BAP and 0.45 µM TDZ produced shoot proliferation followed by elongation in basal medium. The elongated shoots produced roots in media supplemented with 16.11 µM NAA. With this established protocol, ~ 5940 rooted plantlets could be harvested after 40 weeks from a single embryoid. Genetic stability analysis of the plantlets using inter simple sequence repeat markers recorded only 0.05% genetic polymorphism. The plantlets were hardened in a mist house for 8 weeks, and then to 50% shade house for another 16 weeks, and the well-established 6-month-old nursery plants, reintroduced to selected forest segments, exhibited 86% field establishment even after 3 years of observation. Thus, the mass multiplication system developed could be a breakthrough for large-scale multiplication of C. thwaitesii to ensure continuous supply of quality planting material to the cottage industry through the development of agroforestry systems. Furthermore, the in vitro culture system developed here can be replicated for research activities related to the long-term–short-term conservation, micro-multiplication and sustainable utilization of rare, endangered, endemic, monopodial/single stemmed rattan palms.