|KANTAR, MICHAEL - UNIVERSITY OF MINNESOTA|
|BETTS, KEVIN - UNIVERSITY OF MINNESOTA|
|STUPAR, ROBERT - UNIVERSITY OF MINNESOTA|
|WYSE, DONALD - UNIVERSITY OF MINNESOTA|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2012
Publication Date: 9/1/2012
Citation: Kantar, M., Betts, K., Hulke, B.S., Stupar, R.M., Wyse, D. 2012. Breaking tuber dormancy in Helianthus tuberosus L. and interspecific hybrids of Helianthus annuus L. x Helianthus tuberosus. HortScience. 47(9):1342-1346.
Interpretive Summary: This work is intended to provide a standard operating procedure for sunflower geneticists that are interested in using the species Helianthus tuberosus L. as a donor parent of new and useful genes. This species is clonally propagated by tubers, like potato. Dormancy is a major issue in using this species efficiently in crosses, and there was a need to develop a procedure to rapidly break dormancy in order to use this genetic resource. Gibberellic acid was discovered to be an agent that can rapidly break dormancy in Helianthus tuberosus tubers, thereby giving us a simple procedure to grow this plant in a wide variety of environments and multiple times per year. Previously, the dormancy issue limited us to one generation per year. The impact of greater availability of plants of this species is additional opportunities to discover genes for disease resistance, insect resistance, and perennial habit. These genes can be incorporated into cultivated sunflower by wide hybridization.
Technical Abstract: Helianthus tuberosus L. tubers are dormant from the late fall to the following spring. In the wild, tuber dormancy is broken after exposure to winter cold, resulting in sprouting and shoot development in the spring when environmental conditions are favorable. The dormancy period typically limits H. tuberosus populations to one growth cycle per year. An efficient method for breaking tuber dormancy would allow for an additional growth cycle each year, which could be grown in winter nursery or greenhouse conditions. The objective of this research was to compare chemical and cold temperature treatments for artificially breaking tuber dormancy in twelve genotypes of H. tuberosus and interspecific hybrids of Helianthus annuus L. x H. tuberosus. Five cold exposures (2, 4, 6, 8, 10 weeks at 2°C), three plant hormones (ethylene, cytokinin, and gibberellic acid), and one untreated control were examined. All three chemical hormone treatments broke dormancy earlier than even the best cold treatments. Gibberellic acid was the best chemical treatment, initiating plant growth within 6.5-11.5 days in the majority of genotypes tested. The best cold treatment was exposure to 2°C for eight weeks, showing plant growth 63.6-67.5 days following treatment initiation, which was far inferior to the hormone treatments. The gibberellic acid treatment strategy described here may not need further optimization, as 6.5-11.5 days of dormancy is short enough to allow for two growth cycles of H. tuberosus a year.