II. 17 Chromosome doubling at various growth stages of barley haploids with colchicine.
K. M. Ho, D. P. Shanks, W. C. Smith and P. C. Ma, CIBA-GEIGY SEEDS LTD., Ailsa Craig, Ontario, Canada, NOM 1AQ.
The techniques used for chromosome doubling of barley haploids with colchicine have been reported by Jensen (1974), Subrahmanyam and Kasha (1975), and Thiebaut and Kasha (1977). However, the efficiency of chromosome doubling with colchicine at various growth stages of haploids has not been extensively studied. This report presents the results of chromosome doubling treated at various growth stages of barley haploids.
The combination of 0.1% colchicine plus 2% dimethyl sulfoxide (DMSO) in an aqueous solution as suggested by Subrahmanyam and Kasha (1975) was used throughout this study for chromosome doubling. The procedures of chromosome doubling described by Jensen (1974) and Subrahmanyam and Kasha (1975) were followed. Five different treatments were used in this study: (A) treated at the three leaf stage in culture vials and the roots rinsed in water after colchicine plus DMSO was applied, (B) treated at the tillering stage (2-3 tillers) and rinsed, (C) treated at the tillering stage but not rinsed, (D) treated at the erecting stage (pseudo-stem erecting) but not rinsed, and (E) treated and rinsed after the first treatment failed.
During 1975-1977, more than 5,000 barley haploids were treated at various growth stages with colchicine plus DMS0. The results are presented in Table 1. The percentage of haploids doubled increased significantly from 23% in Treatment A to 50% in Treatment B, indicating that the application of colchicine plus DMS0 was more effective at the tillering stage than at the three leaf stage. The delay of the application from the tillering stage (Treatment C) to the erecting stage (Treatment D) resulted in a decrease of the percentage of doubling from 46% to 29%. In summary, the chromosome doubling of haploids with colchicine plus DMS0 at the tillering stage was more efficient than at the earlier stage (three leaf stage) or at the later stage (erection stage).
The percentage of haploids doubled was 22% in Treatment E. It appears that it is worthwhile to re-treat the haploid after the first treatment has failed. Although the haploid plants used in Treatment E had been previously selected (only those with good regrowing tillers were treated), the treatment still led to a mortality of 27%, which was significantly higher than those in Treatments A and B (20% and 10% respectively). Furthermore, Treatment E took a longer time to obtain new tillers. Consequently, it required more growth room space than did other treatments.
There was no difference in the percentage of haploids doubled with (Treatment B) or without (Treatment C) rinsing the roots in water after the treatment. But the mortality increased significantly from 10% with rinsing to 42% without rinsing. If the second treatment of chromosome doubling is expected, it is recommended to rinse the roots after the application of colchicine plus DMS0.
Acknowledgements:
We thank Dr. K. J. Kasha for technical advice and the I.R.A.P. Cereal 198 Grant for partial financial support. A special thanks to our Research and Development Director, G. E. Jones for reviewing the manuscript.
References:
Jensen, C. J. 1974. Chromosome doubling techniques in haploids. In: Haploids in higher plants - Advances and potential. Edited by K. J. Kasha. University of Guelph, Canada. pp. 153-190.
Subrahmanyam, N. C. and K. J. Kasha. 1975. Chromosome doubling of barley haploids by nitrous oxide and colchicine treatments. Can. J. Genet. Cytol. 17:573-583.
Thiebaut, J. and K. J. Kasha. 1977. Experiments on chromosome doubling of barley haploids with colchicine. BGN 7:63-66.
