Germination and viability of wild sunflower species seeds stored at room temperature and low humidity for 38 years

The effects of prolonged storage on the germination and viability of seeds of sunflower crop wild relatives stored under less-than-optimal conditions in working genebanks is not known. Seeds of two wild annual species, Helianthus annuus (common wild sunflower) and annual H. petiolaris (prairie sunflower), were stored at room temperature (20 to 22°C) and low humidity of ~ 22% in the laboratory for 38 years. Germination of stored annual sunflower seeds was 5.5%, while that of prairie sunflower seeds was 0.75%, compared with the germination of freshly harvested seeds of 34.7 and 18.5%, respectively. Tetrazolium, a vital stain, indicated that the seeds were alive. The viability equations were used to predict final viability of the stored seeds. Using the three tests of viability (germination with and without gibberellic acid, and tetrazolium staining), all appeared to underestimate the actual condition of the stored seeds of annual sunflower, but provided better predictions for prairie sunflower. This study indicated that wild sunflower seeds can be stored at less than ideal conditions in working genebanks where viability decreases over time reducing germination, but gibberellic acid treatment can sustainably increase germination to produce a number of plants to maintain the genetic integrity of the original stored seeds often used in long-term prebreeding programmes.