Effect of length and developmental stage of spike on the induction and differentiation efficiency of callus tissue in winter wheat. Evidence for generative development of regenerated plants

The capability of various immature inflorescence fragments of winter wheat cv. Grana to regenerate via callus was studied. The induction and regeneration efficiency of callus derived from spikes at different developmental stages (2-50 mm in length) was determined. Callus was initiated from the following organs of spike: whole segments of the youngest spikes (pairs of spikelets with a part of rachis), single spikelets and rachis of the middle stage spikes and finally individual flowers within spikelets excised from the oldest spikes. Morphogenic callus, capable to regenerate new plants, was obtained from segments derived from spikes being at early stage of organogenesis (2-10 mm in length) and distal flowers (3rd and 4th order) within spikelets of most advanced spikes (41-50 mm in length). Explants derived from spikes at the middle stage of organogenesis (11-40 mm in length) were not able to regenerate into new plants. No regeneration occurred also from developed rachis and glumes. All regenerants obtained in this study reached heading phase without additional vernalization, they were fertile and produced normally formed grains. It indicates that callus transferred the physiological state of the mother tissue i. e. the readiness to flowering.