Cucumber (Cucumis sativus L.) seeds of `Marketer', `Marketmore', `Wisconsin SMR-18', `Tablegreen', `Spotfree', and `China' were stored at 3C and 38% relative humidity for up to 26 years. Seed older than 13 years did not germinate. Cultivars stored 10 years gave 80% germination, except Wisconsin SMR-18' (40%). Ten-year-old seeds were separated from their seedcoats, and cotyledons were excised into six segments. Explants were placed on Murashige and Skoog medium with all combinations of BAP (0, 1,2, and 3 mg·liter-1) and NAA (0, 0.1,0.2, and 0.3 mg·liter-1). Plants were obtained from culture for all cultivars grown on medium containing NAA and 1 mg BAP/liter. No plants were regenerated when BAP or NAA was lacking. Chemical names used: benzylaminopurine (BAP), 1-naphthaleneacetic acid (NAA).
Nawab Ali, Robert Skirvin, Walter E. Splittstoesser, and William L. George
Nawab Ali, Robert M. Skirvin, and Walter E. Splittstoesser
Nawab Ali, Robert M. Skirvin, Walter E. Splittstoesser, David E. Harry, and William L. George
Seed lots with the genetic background of `Baroda' and `Marketer' cucumber (Cucumis sativus L.) containing all possible combinations (DF Df, Dfdf, dfdf) of df (which increases dormancy) and Df (wild type) were used. Dormancy was not solely due to the genotype dfdf and clear effects of genetic background were apparent. The df allele in the homozygous state induced a strong dormancy in `Baroda', but the Df gene could not restore normal germination. However, Df did reduce the dormancy period to 85 days. In `Marketer', df did not delay germination. Any treatment (puncturing, removal, cutting) that damaged the inner integument allowed `Baroda' dfdf to germinate, indicating an intact integument was essential for maintaining dormancy in this cultivar. All `Baroda' dfdf embryonic axes without the cotyledons germinated in 5 days. `Baroda' dfdf seeds with intact integuments imbibed adequate water to germinate but remained dormant, suggesting that the effect of the integument on dormancy was not related to imbibition.