1. Breaking Physiological Dormancy in Tubers of Solanum chacoense Christian T. Christensen 1, Lincoln Zotarelli 1, Kathleen Haynes 23 Kathleen Haynes 2,and Mihai Giurcanu 3 1 Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, 2 USDA-ARS, Beltsville, MD 20705, 2 USDA-ARS, Beltsville, MD 20705, 3 Department of Statistics, University of Florida, Gainesville, FL, 32611

2. Outline Introduction Current Challenges ObjectiveMaterialsMethod Preliminary Results Conclusions

3. Dormancy Factors Genetic Makeup Stage of Tuber Development Environmental Conditions during tuber growth and storage –Bethke (2013) Hormone contributions: Abscisic acid (ABA) and Ethylene: induction Cytokinin: loss of dormancy –Suttle (2004)

4. Gibberellins Exogenous gibberellins can be used to break dormancy in potato tubers –Brian et al. (1955) and Hemberg (1985) GA 3 is typically used in seed certification programs –Suttle (2004)

5. Current Challenges Solanum chacoense (chc) has shown difficulty breaking dormancy which may result in uneven emergence

6. Objective To determine an appropriate concentration of gibberellic acid (GA 3 ) and soak time to encourage breaking dormancy in chc

7. Materials and Methods 11 genotypes of chc across four accessions Separated by size evenly across 12 treatments –Small (1.4g avg.) –Medium (2.5g avg.) –Large (5.8 avg.) AccessionGenotypePI #Country Chc AA-3, A-5, A-6PI 275136Argentina Chc BB-3, B-5, B-10PI 320288Argentina Chc CC-6, C-8PI 537025Bolivia Chc DD-6, D-7, D-8PI 566738Paraguay Left to Right: Small, Medium, And Large

8. Materials and Methods Treatments Protocol GA 3 – Fischer Scientific International Inc. GA 3 dissolved in DI water for two hours Tubers were treated with desired treatment Tubers air dried for 30 minutes GA 3 (μg/ml)Soak Time (min.) 05 045 090 505 45 5090 1005 45 10090 1500 45 15090

9. Materials and Methods CRD with 3 replicates Maintained in an incubator at 25 ºC Sprout number every 2 days Study duration of 46 DAT

10. Statistical Analysis Binary logistic regression model- proportion of sprouting SAS statistical package for Windows (SAS Systems for Windows Version 9.2, SAS Institute Inc. Cary, NC, USA) – –PROC GLIMMIX

11. Results EffectNum DFPr > F GA 3 30.0003 Minutes20.6493 Size2<.0001 Genotype10<.0001 GA 3 *Minutes60.2488 GA 3 *Genotype30<.0001 Minutes*Genotype200.8862 GA 3 *Minutes*Genotype600.8543 GA 3 *Size60.8663 Minutes*Size40.9118 GA 3 *Minutes*Size120.9655 Genotype*Size200.1041 GA 3 *Genotype*Size600.9387 Minutes*Genotype*Size400.8396 GA 3 *Minutes*Genotype*Size1200.9573 Main effects –GA 3 –Genotype –Size Interactions –GA 3 xGenotype

12. Main effects: GA 3 Proportion of Sprouting EffectNum DFPr > F GA 3 3 0.0003 Minutes20.5301 Genotype10<.0001 Size2<.0001 B A A A GA 3 concentrations greater than 0 µg/ml were more successful at breaking dormancy overall GA 3 concentrations greater than 0 µg/ml were more successful at breaking dormancy overall Time had no affect on % tuber sprouting

13. Main Effects: Genotype Proportion of Sprouting Genotypes showed large variation in % tuber sprouting EffectNum DFPr > F GA 3 3 0.0003 Minutes20.5301 Genotype10<.0001 Size2<.0001 A B B B C CDCD D D E E E

14. Main Effects: Size Proportion of Sprouting A B C Direct Correlation between tuber size and % tuber sprouting Direct Correlation between tuber size and % tuber sprouting EffectNum DFPr > F GA 3 3 0.0003 Minutes20.5230 Genotype10<.0001 Size2<.0001

15. Interactions: GA 3 x Genotype NS

16. Conclusion Direct Correlation between tuber size and % sprouted tubers Genotypes showed variation in % sprouted tubers with D-6, D-7, and D-8 exhibiting the strongest dormancy Genotypes from Argentina exhibited weaker dormancy mechanisms while those originating from Bolivia or Paraguay exhibited a stronger dormancy mechanism

17. Conclusion GA 3 concentrations greater than 0 µg/ml were more successful at breaking dormancy overall Soak time had no affect on breaking dormancy No single treatment combination broke dormancy across all genotypes

18. Questions

19. Literature Cited Bethke, P. 2013. Potato Tuber Dormancy. USDA ARS Vegetable Crops Research Unit and UW Department of Horticulture Brian, P.W., H.G. Hemming, and M. Radley. 1955. A physiological comparison of gibberellic acid with some auxins. Physiol Plant 8:899-912 Errebhi, M., C.J. Rosen, S.C. Gupta, and D.E. Birong. 1998b. Potato yield response and nitrate leaching as infl uenced by nitrogen management. Agron. J. 90:10–15. Errebhi M, C.J. Rosen, F.I. Lauer, M.W. Martin, and J.B. Bamberg. 1999. Evaluation of tuberbearing Solanum species for nitrogen use efficiency and biomass partitioning. Amer JPotato Res 76:143-151. Hemberg, T. 1985. Potato rest. In: PH Li(ed), Potato Physiology, Academic Press, New York. Pp 353-388 Opena, G.B. and G.A. Porter. 1999. Soil management and supplemental irrigation effects on potato: II. Root growth. Agronomy Journal 91, 426–431. Suttle, J.C. 2004. Physiological Regulation of Potato Tuber Dormancy. Amer J of Potato Res 81:253-262

20. Acknowledgments USDA-ARS Beltsville, MD –Kathleen Haynes: Committee Member –Karen Frazier: T.C. Technician University of Florida –Lincoln Zotarelli: Advisor –Mihai Giurcanu: Statistician –Rebecca Darnell: Committee Member –Charles ‘Ethan’ Kelly: Lab and Field Technician