Effect of different osmopriming treatment on seed germination of two types of radicchio (Cichorium intybus L. var. silvestre)

To improve germination of two types of radicchio (“Rosso di Chioggia”, RCh, and “Bianco di Chioggia”, WCh) various pre-sowing treatments were evaluated. A non-soaked control was compared with seeds primed for 2, 4, 6, 8 hours in plain water (hydropriming) or in solutions containing the following concentration of polyethylene glycol (PEG 6000) and potassium nitrate (KNO3): a) PEG at -0.5, -0.9 and -1.7 MPa; b) KNO3 at -0.12, -0.24 and -0.52 MPa. After soaking, seeds were rinsed and placed in petri-dishes at 20 or 27°C germination temperature. Pre-sowing treatments affected the germination percentage more than the mean time of germination, and the effects were more evident in RCh and when 20°C germination temperature was applied. Generally, the higher germination percentage was obtained with longer hydropriming (6-8 hrs) and with short treatment (2 hrs) with osmotic compounds. KNO3 proved to be less effective than PEG which gave, on average, the best results at -0.5 and -0.9 MPa water potential.