Regeneration from embryogenic callus and suspension cultures of the wild medicinal plant Cymbopogon schoenanthus

Abstract

Somatic embryogenesis and plant regeneration from both callus and suspension cultures of the wild medicinal plant Cymbopogon schoenanthus subsp. proximus has been achieved. The species is rare and confined in its distribution to Africa. A range (0.5 to 8 mg/l) of 2,4-dichlorophenoxyacetic acid (2,4-D) for the induction of embryogenic callus from seed cultures were used. Results show that 1.0 and 4.0 mg/l 2,4-D gave a 90 to 100% frequency of embryogenic callus containing mature embryos within three months of culture. Testing the effect of phosphorus and nitrogen concentrations on somatic  embryogenesis from callus cultures showed that high phosphorus and low nitrogen concentrations enhanced embryo induction. Low NH₄NO₃ enhanced growth and maturation of somatic embryos, while low KNO₃ enhanced germination and shoot production. Suspension cultures were initiated from  embryogenic callus on 0.5, 1.0 and 2.0 mg/l 2,4-D, then plated on 3 different combinations of 2,4-D and 6-benzyl adenine (BA). Mature embryos were highest on both 0.5 and 1.0 mg/l 2,4-D (X = 15.8, 17.3), while shoot germination was enhanced by using BA in the regeneration media. The effect of high  phosphorus concentration in the culture media was significant on both embryo induction and early  maturation (X = 41). Lower ammonium nitrate concentrations enhanced growth and maturation of embryos. Both embryo maturation and the germination of shoots after 6 and 8 months of plating were  best on low ammonium nitrate (X = 36.8 and 27.6 shoots, respectively). The presented embryogenic  system will be of value for the clonal propagation, ex situ conservation and production of bioactive  compounds from this threatened plant species.

Key words: Somatic embryogenesis, gramineae, in vitro culture, proximol, micropropagation, plant conservation, nitrogen, phosphorus.