Cell aggregates in wheat suspension cultures and their effects on isolation and culture of protoplasts.

Fine embryogenic suspension cultures of wheat (Triticum aestivum cv Hartog and Timmo, and T. durum cv D6962) tend to grow into large cell clumps (1-3 mm), resulting in the formation of mixed suspension cultures consisting of both fine and large cell clumps. The cell clumps were separated according to their sizes and cultured as new lines to investigate their growth rate and differentiation potential and the effects of cell aggregate size on protoplast culture. The results showed that the fine clusters (<310 μm) had a higher growth rate but a lower differentiation frequency than the large cell aggregates (310-2000 μm). After 2-4 weeks incubation, all the new lines reformed mixed suspension cultures again. The large clumps (>1100 μm) released fine cell clusters into the medium so it was possible to initiate fine embryogenic suspension cultures from the large clumps. With regard to the isolation and culture of protoplasts, although the highest yield of protoplasts was obtained from the fine cell clusters, the protoplasts isolated from different sized cell aggregates all had similar potential for sustained cell division and plant regeneration.