Efficient Regeneration of Hedychium coronarium through Protocorm-Like Bodies

Abstract

Hedychium coronarium J. Koenig is a multipurpose plant with significant economic value, but it has been overexploited and listed as a vulnerable, near threatened or endangered species. In vitro culture methods have been used for propagating disease-free propagules for its conservation and production. However, explant contamination has been a bottleneck in in vitro propagation due to the use of rhizomes as the explant source. Plants in the family Zingiberaceae have pseudostems that support inflorescences, while rhizomes are considered true stems. The present study, for the first time, reported that the pseudostem bears nodes and vegetative buds and could actually be true stems. The evaluation of different sources of explants showed that mature node explants derived from the stem were the most suitable ones for in vitro culture because of the lowest contamination and the highest bud break rates. Culture of mature node explants on MS medium supplemented with 13.32, 17.76, and 22.20 μM 6-benzylaminopurine (BA), each in combination with 9.08 μM thidiazurin (TDZ) and 0.05 μM α-naphthaleneacetic acid (NAA) induced the conversion of buds to micro-rhizomes in six weeks. More than 96% of the micro-rhizomes cultured on MS medium supplemented with 17.76 μM BA, 6.81 μM TDZ, and 2.46 μM indole-3-butyric acid (IBA) were converted to globular-shaped clumps with protocorm-like bodies (PLBs). Further culture of a piece of the clumps induced more than 15 adventitious shoots. Adventitious roots were produced at the base of adventitious shoots, and plantlets were readily transplanted to a substrate for acclimatization in a shaded greenhouse. The survival rate of the plants in the greenhouse was up to 90%. Plants grew vigorously, and there were no off-types from the regenerated 11,100 plants. Our study also, for the first time, shows that H. coronarium can be regenerated via PLBs, which may represent a new way of the in vitro propagation of H. coronarium. The established protocol could be used for the increased propagation of H. coronarium for conservation or commercial production.