Prediction of seedling emergence in onion (Allium cepa) seed lots through saturated salt accelerated ageing test

The emergence of six seed lots of two onion (Allium cepa L.) cultivars Pusa Red and Pusa Madhvi was compared by standard germination, vigour index, germination at non-standard temperatures, accelerated ageing and saturated salt accelerated ageing tests. Germination tests were conducted at standard (20 degrees C) and non-standard temperatures of 15 degrees C, 25 degrees C and 30 degrees C. The accelerated ageing (AA) and saturated salt accelerated ageing (SSAA) tests were performed using four relative humidity levels, viz. standard AA (RH 100%), NaCl (RH 75%), Mg (NO3)(2) (RH 53%) and CaCl2 (RH 29%). These vigour tests were able to assess vigour differences among different seed lots. The field emergence percentage ranged from 32% to 55.5% in onion seed lots. Field emergence had non-significant correlation with germination at non-standard temperatures of 15 degrees C, 25 degrees C and 30 degrees C. However, accelerated ageing (RH 100%) and saturated salt accelerated ageing using NaCl (RH 75%) showed positive and significant correlation value of 0.943 and 0.957, respectively. The regression analysis results for onion seed lots revealed that standard germination, accelerated ageing (AA) and saturated salt accelerated ageing (SSAA) test using NaCl (RH 75%) explain 88%, 88% and 91% variation in field emergence, respectively. The results suggest that saturated salt accelerated ageing (SSAA) test using NaCl (RH 75%) is useful vigour tests to predict seedling emergence in onion seed lots.