Cytological aspects of isolated microspore culture of Brassica napus

Preculture cytological events within anthers of two genotypes of Brassica napus were examined to detect differences between microspores that have embryogenic potential and those that do not. Microspores of five anthers per bud were cultured, while the sixth anther was fixed for cytological observation. A series of buds of increasing maturity were individually sampled from specific racemes. Correlations of bud, anther, microspore, and nuclear size were drawn to establish physical parameters for each cytological stage. Cytological events and cytophotometrically monitored DNA content were noted for spores of each anther size class. Best embryogenic responses were among populations of microspores in the late uninucleate stage, immediately prior to first pollen mitosis. Typical, rod-shaped, cotyledonous embryos could be generated within 30 days from microspores at this stage at a rate up to 1300/anther. Slightly younger or older microspores had a drastically reduced embryogenic performance. Postculture observa...