Chromosome doubling procedures of onion (Allium cepa L.) gynogenic embryos.
A novel approach for chromosome doubling that consists of treating embryos instead of parts of micropropagated plants was investigated. Following 2-year trials, amiprofos-methyl (APM) was found to be superior to oryzalin on the basis of a lower toxicity, and we were able to narrow the range of concentrations of APM. The addition of 2% dimethyl sulphoxide (DMSO) and 1% Triton X-100 to 25 microM APM had no effect in all treatments. A final experiment with 6,658 embryos demonstrated that a 2-day treatment in liquid media supplemented with 50 microM APM was the most successful with respect to chromosome doubling-36.7% of the plants were diploid-but the survival rate was reduced to 52.5% of that of the non-treated control. A 2-day treatment in liquid medium supplemented with 25 microM APM or a 2-day treatment on solid medium with 50 microM APM resulted in the production of diploids at a frequency of 28.9% and 21.3%, respectively. These may represent alternative methods for chromosome doubling since compared to the untreated control these two treatments reduced the survival rate by only about 24%. Final ploidy and fertility of the large proportion of induced mixoploid plants (up to 30.3%) need to be evaluated in further studies.
Jakse
M
M
Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000, Ljubljana, Slovenia.
Havey
M J
MJ
Bohanec
B
B
D000490:Allium / Q000196:embryology / Q000235:genetics*; D032461:Chromosomes, Plant; D003470:Culture Media; D004121:Dimethyl Sulfoxide; D017830:Octoxynol; D012639:Seeds / Q000235:genetics*
D003470:Culture Media; D017830:Octoxynol; D004121:Dimethyl Sulfoxide