Advantages of embryogenic cell cultures of Gramineae

Immature embryos and/or explants from very young leaves and inflorescences of 13 species and over 75 cultivars of Gramineae - including wheat, maize, rye, pearl millet, sugar-cane, Napier grass, Guinea grass, etc. - were used to initiate callus cultures. The cultures are white to yellowish white in colour, compact and contain small and thin-walled meristematic cells which are richly cytoplasmic, non-vacuolated and contain prominent starch grains. These embryogenic tissue cultures provide a long-term, highly reliable and efficient means of rapid mass clonal propagation by the formation of somatic embryos that arise from single cells. The cultures consist largely of cytologically normal diploid cells. During the process of plant regeneration via somatic embryogenesis, there is strong selection in favour of normal cells, so that plants recovered from such cultures neither exhibit any morphological abnormalities nor show any evidence of cytological changes in the number or structure of chromosomes. Embryogenic callus cultures have been used successfully to establish highly dispersed and friable cell-suspension cultures. These fast-growing cultures comprise groups of 2-6 embryogenic cells, which adhere together to form larger unorganized aggregates of up to about 75 cells, but do not contain any organized meristems or callus tissues. Plants were regenerated by somatic embryogenesis from embryogenic cell-suspension cultures of pearl millet, Guinea grass, sugar-cane and maize. Finally, embryogenic cell-suspension cultures are the only current source of totipotent protoplasts in Gramineae. Protoplasts isolated from such cultures have been successfully cultured to produce somatic embryos and plants in pearl millet, Guinea grass, Napier grass and sugar-cane. (author)