Rapeseed (Brassica napus L.) response to salinity and seed priming with NaCl

Laboratory and pot trials were conducted to study germination performance of rapeseed (Brassica napus L., genotype Excalibur) under NaCl salinity after seed priming with 20 mM NaCl for 24 h. In the laboratory trial, salinity levels of 80, 160, and 240 mM NaCl reduced the germination percentage by 14, 56, and 80 percentage points, respectively compared to the non-saline control. NaCl priming lowered the detrimental effect of salt stress on germination by promoting germination from 81% to 85% under salinity of 80 mM, from 39% to 68% under salinity of 160 mM, and from 15% to 56% under salinity of 240 mM NaCl (maximum alleviation). Furthermore, NaCl priming increased the germination tolerance index and the vigour index of seedlings as compared with the control seeds. Relative water content of the leaves was decreased with increasing salinity, showing limited water availability and a loss of turgor in the leaves. NaCl priming reduced the decrease in relative water content under salinity. Concerning the pot trial, the salinity level of 240 mM NaCl reduced the dry weight of rapeseed seedlings by 80.9% in the non-primed seeds and by 55.8% in the primed seeds. NaCl priming improved the mean productivity index by 1.26 times under salinity of 240 mM NaCl and the harmonic mean index by 1.98 times under salinity of 240 mM NaCl compared with non-primed seeds. Salinity limited seed performance of rapeseed, whereas NaCl priming improved seed performance and early growth in saline environment. The priming method needs to be examined in a selection of relevant genotypes under a range of saline conditions.