Seedling emergence in winter and spring canola genotypes under salinity stress

In the worldwide context of rising salinity issues in agriculture, it is important to understand crop responses to salinity stress. Currently, standing as the second largest oilseed crop, canola (Brassica napus L.) entices continued research focus on such aspects. Thus, this study investigated the genotypic variation in seedling emergence characters under salinity stress. Two growth chamber experiments were conducted in diverse canola genotypes (10 each of winter and spring types) at six salinity levels (0, 2, 4, 6, 8, and 10 dS m(-1) EC). Increasing salinity levels reduced the emergence indices (emergence percentage, emergence rate index, corrected emergence rate index, and emergence velocity) and salt tolerance index (STI). An approximate threshold salinity range of 6-8 dS m(-1) ECs was determined. Importantly, salinity at >= 8 dS m(-1) EC levels substantially reduced seedling emergence indices and delayed emergence by 3-7 days after seeding. Winter genotypes CP1022WC/Chinook and CP320WRR, and spring genotypes Monarch, PI597352, PI601200, and PI432395 had higher STI and emergence indices. Based on cluster analysis, genotype groups were classified as low (Athena, CP115W, Durola, Impress, and Gem), medium (Amanda, Ericka, CP320WRR, Salut, CP225WRR, Clearwater, and Wester), and high salt-tolerant types (CP1022WC/Chinook, Monarch, PI597352, and PI432395). All emergence indices showed high broad-sense heritability (H-2 = 0.82-0.94). Between canola types, spring canola consistently showed greater genetic potential for salt tolerance than winter canola. The results of this study provided useful information for canola seedling establishment under salinity and for further genetic improvement of salt tolerance.