II.38. Feeding of detached tillers improves haploid production in barley.
N. C. Subrahmanyam and K. J. Kasha, Crop Science Department, University of Guelph, Guelph, Ontario, Canada.
The interspecific cross between diploid Hordeum vulgare L. and H. bulbosum L. results in haploids (monoploids) of H. vulgare following embryoculture techniques (Kasha and Kao, 1970). Gibberellic acid treatment of the pollinated florets increases the frequency of such haploid progeny (Subrahmanyam and Kasha, 1971).
In an attempt to further improve the frequency of haploid seedlings in barley, we followed up the suggestion of C. J. Jensen, Danish Atomic Energy Research Station Riso, Roskilde, Denmark, of feeding detached tillers. Emasculations of vulgare florets (var. York) and pollination with H. bulbosum (line GBC-77) were done in the same way as we reported earlier. On the day following pollination, the tillers were severed from the plant 1/2" - 1" above the second node from the top and inserted into nutrient solution (modified Hoagland's solutions as in Table 1). The controls were left on the parent plant. Containers were mostly 250 ml beakers with a plastic top through which holes had been punched although plastic trays (14" x 9" x 3 1/2") are presently used in handling large numbers of tillers. The solution was replaced at 2 days interval to avoid algal growth and the cut end of the tiller was trimmed at each change of solution. Seeds were harvested 14 days after pollination and excised embryos were cultured as in earlier reports (Kao and Kasha, 1969; Kasha and Kao, 1970).
The results (Table 2) indicate that the frequency of seedlings (haploids) obtained was higher from detached tillers fed with nutrient solution. The average seedlings obtained through nutrient solution feeding in combination with GA treatment (on florets) was 23% as compared to 14.8% for the control. Additional studies comparing nutrient solution with water and using different methods of applying GA are summarized in Table 3. Treatment with 6 ppm of GA in nutrient solution for 2 days was better than the control.
The embryo size following cut stem feeding was also increased and enabled easy disection of seeds at the time of culturing. The number of visibly differentiated embryos was also found to be increased significantly. The majority of the seedlings obtained were from the differentiated embryos and further studies of this aspect are in progress.
Acknowledgements
Our appreciation is extended to Dr. L. A. Hunt, Crop Science Department,
University of Guelph, for permission to quote his unpublished composition
of the nutrient solution. Supported by a National Research Council Grant.
References:
Kao, K. N. and K. J. Kasha. 1969. Haploidy from interspecific crosses
with tetraploid barley. Barley Genetics II:82-89.
Kasha, K. J. and K. N. Kao. 1970. High frequency haploid production in barley (Hordeum vulgare L.). Nature, 225:874-876.
Subrahmanyam, N. C. and K. J. Kasha. 1971. Increased barley haploid production following gibberellic acid treatment. Barley Genetics Newsletter, 1:47-50.
