We previously reported (MGCNL 59:73, 1985) that 20% of normal spikelets of cultured maize tassels extrude anthers with elongated filaments. We report here the procedure for recovering the pollen from these extruded anthers, some characteristics of the pollen and its germination, and also fertilization and seed production with in vitro-derived pollen.
After 16-25 days of tassel culture (MGCNL 59:72, 1985), extruding anthers of both cv. Oh43 and Se60 tassels were excised separately, dried on Whatman #1 filter paper in a desiccator containing a mixture of dehydrated silica gel and CaCl2 for 1/2 to 5 h. Fresh pollen, collected within 1/2 h after drying of the anthers, was used for measuring the characteristics listed in Table 1. Germination percentage and tube growth rate were calculated from pollen germinated on nutrient agar medium (Can. J. Bot. 43:779, 1965). As indicated, in vitro-produced pollen and greenhouse pollen were similar in the measured parameters.
The in vitro-produced pollen also germinated on receptive silks. For observations on in situ germination, ears with receptive silks were pollinated with fresh pollen and the general procedure of fixing, clearing, staining with aniline blue and fluorescence microscopy (Naturwissen. 44:1, 1957) was followed. No observable differences were detected between in vitro pollen and native pollen during germination and tube growth in or on silks.
The in vitro-derived pollen also fertilized ovules and produced viable seed. Female parent plants were grown in plastic pots in greenhouse, detasseled and bagged prior to the emergence of silks. The plants were moved to the laboratory and ears were pollinated with pollen collected after 1/2 to 5 h of drying of extruded anthers under monitored conditions in March and April, 1985.
All ears pollinated with pollen collected within 5 h after drying of anthers produced kernels. But the number of kernels produced per ear declined with increased drying time of anthers. Nevertheless, with generous application of fresh pollen, collected within 1 h after drying of anthers, up to 300 kernels per ear were produced. Kernels had 100% germinability and yielded normal, fertile, genetically true plants during summer, 1985.
The demonstration that the cultured tassels produce normal, germinable and viable pollen, and that the pollen is essentially similar to native pollen, suggests that the system has considerable potential for both basic and applied research.
D. R. Pareddy, R. I. Greyson and D. B. Walden
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