Evaluation of various methods to break dormancy of potato (Solanum tuberosum L. 'Granola') minitubers

Different postharvest treatments were used to evaluate dormancy break in 'Granola' potato (Solanum tuberosum L.) minitubers. Treatments included ethephon (5,000 and 10,000 µL L^-1), modified atmosphere packaging (MAP) using 0.002 mm polyethylene bags (PEB), calcium carbide (CaC₂,3 and 5 g kg^-1) plus MAP, gibberellic acid (GA₃, 1 and 5 µL L^-1) and 1-methylcyclopropene (1-MCP, 1 and 10 µL L^-1, 48 h). As early as 3 weeks or at opening of the PEB, minitubers treated with 3 g kg^-1 CaC₂ and MAP had the highest sprouting percentage of 50%. This trend was consistent up to nine weeks of storage wherein 3 g kg^-1 CaC₂ and MAP treatments resulted in highest sprouting percentage (71 and 72%, respectively). Treatment of 3 g kg^-1 CaC₂ gave the highest weight loss (11%) at 12 weeks. Sprouting resulting from the different treatments ranged from 60 to 77% at 12 weeks, indicating long dormancy in 'Granola' minitubers. The ethephon and 5 µL L^-1 GA₃ treatments exhibited more than 50% sprouting at 9 weeks after treatment (WAT), but not the control, 1 µL L^-1 GA₃ and 1-MCP. Dormancy break with the use of CaC₂ (3 g kg^-1) resulted in most sprouts per minituber (2.9) and longest apical sprouts (3.5 mm) relative to the control (0.90 and 1.4 mm, respectively). However, CaC₂ and MAP treatments resulted in greater minituber decay at four weeks.