Previous workers have championed the potential of pollen as a "window" through which fresh insights on the life cycle will be gleamed and hereditary transformation might be induced (K. Raman et al., J. Hered. 71:311, 1980; R. Flavell and R. Mathias, Nature 307:108, 1984; J. H. Krieger, Chem. Eng. News, Oct. 1984, p. 16). What might be true for normal pollen should be equally true for pollen derived from the tassel culture system, if in fact the pollen is normal, germinable and viable. Polowick (M.S. thesis, UW.O., 1981; Can. J. Bot., in press) documented the apparently normal cytogenetic features of pollen development in Seneca 60. The present report extends these observations to Oh43 and documents the in vitro germinability of this pollen.
Cultured tassels grow in vitro and produce spikelets after 16-20 days for cv. Seneca 60 and 20-25 days for cv. Oh43. Frequently, of the 100-200 normal spikelets per tassel, 5-20% yield extruded anthers with elongated filaments. Pollen from these extruded anthers, when spread on the surface of Cook and Walden Basal Medium (CWBM) (Can. J. Bot. 43:779, 1965) with an agar content of 1.5%, germinates well. For both Seneca 60 and Oh43, 40-50% of the pollen grains (Table 1) produce pollen tubes, while 30-40% of the grains possessing apparently normal cytoplasm remain ungerminated. Germination from unextruded anthers is also observed (8-11%), but at a reduced rate for both cultivars. In these, a much higher frequency (~25%) of "ghosts" is observed.
The in situ germinability of this in vitro derived pollen has yet to be demonstrated convincingly. Other than minor technical complications, we foresee, however, no serious reason why pollen from the tassel cultures cannot be used to produce viable embryos-whether in vivo or in vitro. When this is achieved, tests which attempt to introduce foreign hereditary factors into the pollen can be attempted.
Table 1: Summary of data from a number of experiments on germination on CWBM of pollen derived from cultured tassels.
D. R. Pareddy, R. I. Greyson and D. B. Walden
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