Submitted to: Seed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2010
Publication Date: 12/1/2010
Citation: Seiler, G.J. 2010. Germination and viability of wild sunflower species achenes stored at room temperature for 20 years. Seed Science and Technology. 38:786-791.
Interpretive Summary: Storage of seeds in genebanks has been the most common technique for the conservation of plant genetic resources over decades or centuries. In most base genebank collections, 3 to 7% seed moisture and 0 F or lower storage temperature theoretically assure seed viability, vigor, and genetic integrity for thousands of years. While optimal storage conditions have predictable results, the effects of prolonged storage on germination and viability of seeds of wild sunflower species stored under less than optimal conditions is not known. Knowledge of this would facilitate the long-term storage of wild sunflower seeds in genebanks and under less than ideal storage conditions. The objectives of this study were to: 1) test the germination of wild annual and prairie sunflower seeds stored at room temperature for 20 years, 2) determine the viability of the seeds, and 3) determine if the germination of the seeds could be enhanced by using gibberellic acid. Germination for wild annual sunflower seeds stored for 20 years was 13%, while prairie sunflower had only 1.5% germination. Germination percentage of fresh seeds 20 years ago was 35% for wild annual and 18.5% for prairie sunflower. Viability testing indicated that the seeds were alive, but dormant, resulting in very low germination after a long storage period. Wild annual sunflower seeds had 90% positive staining using the tetrazolium viability test indicating that they were alive, while prairie sunflower seeds had 80% staining. Pre-treating the seeds with gibberellic acid for one hour increased germination of the wild annual sunflower stored for 20 years from 13% to 88%, and prairie sunflower from 1.5% to 85%. This information indicates that seeds stored for long periods of time should not be discarded due to their low germination since they may still be viable, and only in a deep state of dormancy, and can be induced to germinate using gibberellic acid. The results of this study will be useful for genebank curation and others where wild sunflower seeds may have been stored for long periods, sometimes under less than ideal storage conditions. The seeds are dormant and should not be discarded due to their low germination. Treatment of the low-germinating dormant seeds with gibberellic acid should break the dormancy, allowing for the regeneration of the population.
Technical Abstract: Storage of seeds in genebanks has been the most common technique for ex situ conservation of plant genetic resources. Storage times and conditions affect the longevity of the seeds. It is not known what detrimental effects, if any, that storage of achenes of wild Helianthus species at less than optimal conditions for long periods of time would have on their viability and germination. The objectives of the study were to test the germination and viability of achenes of two wild annual sunflower species, H. annuus (common wild sunflower) and H. petiolaris (prairie sunflower), stored at room temperature (20-22 C) at a relative humidity of approximately 22% in a bell jar in the laboratory for 20 years, and to determine the efficacy of a germination technique using gibberellic acid (GA3) as a medium to overcome dormancy and increase germination. Germination for wild H. annuus achenes stored for 20 years was 13%, while H. petiolaris had only 1.5% germination. Germination percentage of fresh achenes 20 years ago was 35% for H. annuus, and 18.5% for H. petiolaris. Viability testing indicated that the achenes were alive, but dormant, resulting in very low germination after a long storage period. Wild H. annuus achenes had 90% positive staining using the tetrazolium viability test indicating that the achenes were alive, while H. petiolaris achenes had 80% staining. Treating the wild achenes with 1 mM GA3 for one hour increased germination of the wild H. annuus achenes stored for 20 years from 13% to 88%, and H. petiolaris from 1.5% to 85%. This information indicates that achenes stored for long periods of time should not be discarded due to their low germination since they may be still viable, but in a deep state of dormancy, and can be induced to germinate using GA3. This information will be useful for genebank curation.