Determination of tobacco (Nicotiana tabacum) seed vigour using controlled deterioration followed by a conductivity test

Seeds of eight lots of four tobacco varieties differing in vigour were studied. The initial germination percentage (GPUT) was 81-100% and the controlled greenhouse emergence percentage (CEP) was 55-91%. All seeds were treated by controlled deterioration (CD) at 20% moisture content and 45 degrees C for 24 hours, then some seeds were subjected to a standard germination test and the rest of the seeds were subjected to a conductivity test. The electrical conductivity (EC) of seed soak water was measured every six hours up to 54 hours. The results showed that relative conductivity after CD (RCCD) was highly significantly correlated with GP(CD) after 30 to 48 hours soaking (r = -0.9324 to -0.9409, P < 0.001). After 36 and 42 hours, RCCD was significantly correlated (P < 0.01) with CEP (correlation coefficients of -0.9120 and -0.9137, respectively). Therefore, it is suggested that measuring relative conductivity after CD could be used to rank tobacco seed lots for vigour. In addition, the best seed soaking time for EC measurement is 36 to 42 hours, with respect to both efficiency and accuracy.