Somatic Embryogenesis and Plant Regeneration of Wiregrass (Aristida stricta) and Creeping Bluestem (Schizachyrium scoparium var. stoloniferum)

Abstract

Initiation of callus and induction of embryogenesis were achieved from both wiregrass and creeping bluestem. MS basal medium containing coconut milk, sucrose, and 2,4-D were used to initiate callus from young inflorescence of wiregrass and creeping bluestem. The presence of 2,4-D was found to be essential for the induction and early development of embryoids, possibly up to the globular stage. In the case of bluestem, initiation of embryogenic callus required the presence of a low concentration of BA; using only 2,4-D resulted in more non-embryogenic callus. More globular embryos were formed when embryogenic cultures grew rapidly without subculturing, or after being transferred to a hormone-free or a reduced 2,4-D medium. Plant regeneration was carried on a hormone-free MS medium. Initiation of cell suspension and induction of embryoid formation of wiregrass were achieved. However, maintaining cell suspensions seems to have some problems. A majority of the cells were thick-walled, elongated, and non-dividing. No embryos were formed in suspension cultures planted onto solid media. Reinitiation of cell suspension culture of wiregrass is in progress. Initiation of creeping bluestem cell suspension culture was carried out in MS basal medium containing coconut milk, sucrose, and 2,4-D. The maintenance of the cell suspension cultures and induction of embryoid formation were tested under different combinations and concentrations of growth regulators. Suspension cultures were selected and planted onto semi-solid MS basal medium with or without growth regulators. Somatic embryoids formed from suspension culture 3 to 4 weeks after being planted on semi-solid medium. Germination and plant regeneration of somatic embryoid of creeping bluestem are in progress.