Isolated microspore culture of Chinese flowering cabbage (Brassica campestris ssp. parachinensis).

Microspores of several genotypes of Brassica campestris ssp. parachinensis have been cultured in vitro and induced to undergo embryogenesis and plant formation. Conditions favourable for embryogenesis in this species include a bud size of 2-2.9 mm, NLN-13 culture medium (Nitsch and Nitsch 1967; Lichter 1981, 1982; Swanson 1990), and an induction through exposure to 32°C for a period of 48 h. Longer periods of an elevated temperature for induction of embryogenesis resulted in embryo abortion at early developmental stages. With the protocol developed here, microspores of 60-80% of donor plants could be induced to produce embryos, although embryo yields were low, i.e. 2-5 embryos per 10 buds. Some genotypes responded to culture conditions with high numbers of embryo formation (100-150 embryos per 10 buds) but most of these subsequently failed to mature. The pattern of cell division and morphological changes of the microspores in culture were studied using various microscopic techniques.