Comparative Evaluation of the Effects of Gibberellic Acid Concentrations on Dormancy Break in Tubers of Solanum chacoense

Solanum chacoense is a wild relative of potato (Solanum tuberosum) that is of interest because of its many desirable traits, but it exhibits variations in tuber dormancy across accessions. The objective of this study was to determine an appropriate gibberellic acid (GA(3)) concentration and soak time treatment to encourage sprout development across four accessions of S. chacoense (A, B, C, and D) from the 174 accessions of the U.S. Department of Agriculture Potato Genebank. Twelve treatments were created by using four concentrations of GA(3) (0, 50, 100, and 150 mu g.mL(-1)) across three soak periods (5, 45, and 90 minutes). Small (average weight, 1.4 g), medium (2.6 g), and large (5.6 g) tubers were distributed among all treatments. Percentage of tubers sprouted, time to sprouting, sprout length, and sprout number per tuber were analyzed to determine the effectiveness of GA(3) treatments on dormancy breaking. GA(3) concentrations of 50, 100, and 150 mu g.mL(-1) partially broke dormancy within accessions B and C. None of the tested treatments were effective for breaking dormancy in accession D within 46 days after treatment. Accession A showed weaker dormancy, thus producing a similar percentage of sprouted tubers across all GA(3) treatments. Soak time had no significant effect on all parameters measured. Larger tubers produced greater sprout number per tuber and percentages of sprouted tubers. Soaking tubers in 50 mu g.mL(-1) of GA(3) may be an effective treatment for S. chacoense accessions with mild dormancy, but alternative methods to break dormancy may be required for S. chacoense accessions with stronger dormancy.