In vitro regeneration of Hypoxis colchicifolia plantlets

Corms of Hypoxis species are heavily traded for use in traditional medicine in southern Africa. High demand has increased unsustainable harvesting from the wild, diminishing natural populations. Micropropagation of Hypoxis colchicifolia was investigated as a means of mass producing plants for both commercialization and re-establishment in the wild. Various plant organs were tested as explant sources and decontamination optimized for each explant type. Seeds failed to germinate in vitro, and inflorescence peduncles, leaves (young and mature) turned brown and did not respond in culture. Only 6% of corm explants produced callus and shoots. Flower buds responded best, with multiple shoots initiated from explants either directly from meristemoids or indirectly via callus. The problem of browning due to phenolic exudation was solved by including polyvinylpyrrolidone (PVP) in the culture medium when required. Common pathogens were partially controlled by washing affected explants in benomyl solutions. Rooting and corm induction were successful, and plantlets could be stored at low temperature (10 °C) prior to acclimatization with no adverse effects. In planting trials with 5-month-old and 21-month-old plants regenerated using the improved protocols, flowering percentage, corm and leaf size were increased significantly in plants grown in pots compared to those grown in the field over a 28 month period.

► An in vitro propagation method for Hypoxis colchicifolia was established.
► Seeds, inflorescence peduncles and leaves did not respond to in vitro culture.
► Only 6% of corm explants and 53% of flower explants produced shoots or callus.
► Browning was partially controlled by addition of PVP and activated charcoal.
► Acclimatized plants grew faster in pots and flowered sooner than field-grown plants.