Effect of Type and Application Time of Chemicals on Dormancy Breaking of Potato Minitubers

In this study, the effect of application time (immediately and one week after harvest) of some chemicals (rindite, carbon disulphide, gibberellic acid and thiourea) on breaking of dormancy and sprouting of potato (Solanum tuberosum L., cv., Marfona) minitubers was investigated. For the carbon disulphide (25 ml m-3 for four days) and rindite (0.2 ml L-1 for two days) application, minitubers were exposed to evaporation of these materials in plastic containers with tightly fitting lids, immersed in solution of thiourea (30 g L-1 for two hrs) or gibberellic acid (50 mg L-1 for two hrs). Results showed that time of application had a significant effect on breaking of potato minituber dormancy. Rindite and carbon disulphide immediately and gibberellic acid and thiourea in one week after harvest had a greater effect. Irrespective of time of treatment, minitubers were treated with rindite and thiourea had the lowest and the highest dormancy period, respectively. The number, length and fresh weight of sprout in treated minitubers significantly enhanced by treating minitubers with chemicals compared with the untreated control minitubers, but there were strong interactions between chemicals and time of treatment. Rindite and carbon disulphide immediately and gibberellic acid and thiourea in one week after harvest had a greater effect on sprouting. Sprout mass per unit of sprout length of the longest sprout were significantly increased by treating minitubers with rindite, thiourea and carbon disulphide compared with the untreated control minitubers, but in gibberellins treated minituber decreased.