Because of their small size, minitubers have a long period of dormancy, which leads to delayed and uneven shoot emergence and makes them unsuitable as the planting material for commercial crops.
In the experiments reported here, micropropagated plantlets of the potato 'Marfona' were raised in a peat and perlite mix in a greenhouse and minitubers were harvested from them. Freshly-harvested minitubers plus others harvested a week earlier were immersed for one, two or three hours in water or in solutions containing from 10mg to 100mg of gibberellic acid per litre.
They were air-dried and placed in the dark at 25 degsC and 85 per cent relative humidity. They were regarded as having sprouted once they had at least one 2mm sprout and the "duration of dormancy" was the time taken for 80 per cent of the minitubers to sprout.
Gibberellic acid shortened dormancy, increased the number of sprouts and was more effective on freshly-harvested tubers. The optimum treatment prior to planting was to immerse freshly-harvested minitubers for two hours in a solution containing 25mg per litre of gibberellic acid.
Effects of Concentration and Propagule age on the Efficacy of Gibberellic Acid for Breaking Dormancy in Potato Minitubers by Salimi, Hosseini, Tavakkol-Afshari and Struik (2010). Journal of Horticultural Science & Biotechnology 85 (6): 461-464. The authors' abstract of their manuscript can be seen in full at www.jhortscib.com
Dr Ken Cockshull is associate fellow, Warwick Crop Centre, University of Warwick