SUNFLOWER GERMPLASM DIVERSIFICATION AND CHARACTERIZATION UTILIZING WILD SUNFLOWER SPECIES, CYTOGENETICS, AND APPLIED GENOMICS
Location: Sunflower Research
Title: Are wild sunflower achenes stored at room temperature for 20 years still alive?
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 6, 2009
Publication Date: March 6, 2009
Citation: Seiler, G.J. 2009. Are Wild Sunflower Achenes Stored at Room Temperature for 20 Years Still Alive?. Proceedings 31st Sunflower Research Workshop, National Sunflower Association, January 13-14, 2009, Fargo, ND. Available: http://www.sunflowernsa.com/research/research-workshop/documents/Seiler_SFachenes_09.pdf
Interpretive Summary: Storage of seeds in genebanks has been the most common technique for conservation of plant genetic resources since the 1970s. In most genebank collections, optimum humidity and storage temperature theoretically assure seed viability, vigor, and genetic integrity for hundreds of years. The effects of prolonged storage of wild sunflower seeds stored at less than optimal conditions on germination and viability are not known. Knowledge of this would help facilitate the long-term storage of wild sunflower achenes in controlled genebanks and under less than ideal storage conditions. The objectives of this study were to: 1) test the germination of two wild annual sunflower species, common annual sunflower, and the prairie sunflower, stored at room temperature for 20 years; 2) determine if the germination of the achenes could be enhanced by using a growth hormone, gibberellic acid; and 3) determine the viability of the seeds. Seeds of common wild and prairie sunflower stored for 20 years at room temperature lost on average 22 and 17% germination, respectively. Viability tests indicated that seeds of the common wild and prairie sunflower had 93 and 85% viability at harvest, respectively, which slightly decreased to 90 and 80% viability, respectively, after 20 years of storage at room temperature and low humidity. Use of a growth hormone, gibberellic acid, overcame the dormancy in seeds, increasing germination from 13 to 88.6% in common wild and from 1.5 to 85.3% in prairie sunflower for seeds stored 20 years at room temperature. This is useful information for genebank curation where seeds may have been stored for long periods of time, and should not be discarded due to their low germination since the seeds are still viable, but in a deep state of dormancy, and can be induced to germinate using a growth hormone.
Dormancy in achenes of wild sunflower (Helianthus) species ensures that they do not germinate in temperate climates until conditions are optimal for seedling survival. Once dormancy is imposed, it suppresses germination, allowing the achenes to survive in nature for years. It is not known what detrimental effects storage of achenes 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 viability and germination of achenes of two wild annual sunflower species, H. annuus and H. petiolaris, 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. The tetrazolium test was used to test the viability of the achenes of the wild species. Wild H. annuus had 90% positive staining after 20 years of storage indicating achene viability vs. 93% at harvest, while H. petiolaris had 80% staining after storage vs. 85% at harvest. Germination using a standard technique for wild H. annuus was 13%, while H. petiolaris had only 1.5% germination. Germination of fresh achenes 20 years ago was 35% for H. annuus, and 18.5% for H. petiolaris. Treatment of the wild achenes with 1mM GA3 for one hour resulted in an increased germination of the wild H. annuus from 13% to 88%, and H. petiolaris from 1.5% to 85%. Viability testing indicated that the achenes were alive, but due to dormancy, they had very low germination after their long storage period. While the germination percentage appears to decrease with storage time, the achenes are still viable and can be induced to germinate using GA3. Priming or infusion of chemicals into achenes greatly enhanced germination. This is useful information for genebank curation where achenes may have been stored for long periods of time, but should not be discarded due to their low germination. Chemical treatment of the low-germinating achenes from the original population is possible for regeneration of the population accession. This will increase the genetic diversity available for improvement of cultivated sunflower.