Effect of surface coating with waxes on the dormancy of potato tubers grown from true potato seed (TPS)

The control of dormancy is of great importance for the long-term storage of potato tubers. The effect of tuber coating with two waxes (paraffin wax and the edible wax 'Teycer', based on shellac and oxidised polyethylene) on the dormancy, weight loss, respiration and soluble sugars (glucose, fructose, sucrose) content of tubers grown from true potato seed (IP88008) was studied, using untreated tubers as controls. Tubers were stored for 120 days after treatment (DAT) in the dark at three different temperatures (5, 15, 20 degrees C) and 80 +/- 5% R.H. Paraffin wax and 'Teycer' did not affect tuber dormancy at 5 degrees C. In comparison with the controls, paraffin-treated tubers had a lower number of sprouted buds after the 42nd (15 degrees C) and the 35th (20 degrees C) DAT, lower weight loss (5, 15 degrees C) and lower respiration rate up to the 15th (5 degrees C) and the 5th ( 15, 20 degrees C) DAT. However, they presented higher weight loss at 20 degrees C and a higher respiration rate after the 25th and 10th DAT at 15 and 20 degrees C, respectively. In contrast, 'Teycer' increased tuber sprouting after the 7th (20 degrees C) and the 21st (15 degrees C) DAT, as well as tuber weight loss at 5 degrees C, but it had no effect on tuber weight loss at 15 and 20 degrees C. In addition, 'Teycer' caused tuber rotting (18-32%) at all storage temperatures. 'Teycer'-treated tubers had lower respiration rates than the controls from 5 to 15 DAT (5 degrees C) and up to the 10th (15 degrees C) and the 5th (20 degrees C) DAT. However, respiration was higher than the controls after the 40th (5 degrees C) and the 50th (15, 20 degrees C) DAT. In comparison with the control, fructose, glucose and sucrose content was higher in both paraffin-treated and 'Teycer'-treated tubers at all storage temperatures. These findings suggest that paraffin wax effectively controls tuber dormancy at 15 degrees C, whereas the application of 'Teycer' is not satisfactory for the control of tuber dormancy.