Variations in germination and seedling traits of rapeseed (Brassica napus L) genotypes under salinity stress and salicylic acid treatment

Rapeseed is an important oilseed crop in Bangladesh that's germination and seedling growth often get affected in saline-prone regions. This study focuses on assessing the variation in germination and seedling traits of rapeseed genotypes under salinity and dual stress – salinity with salicylic acid. Seeds of five parents and ten F3 segregants of rapeseed (Brassica napus) were subjected to three treatments for eight days— control, 8 dSm-1 salt and 8 dSm-1 salt+0.1mM salicylic acid. The F3 segregants were considered to evaluate the diverse inherent phenotypic expression of traits rather than only fixed genetic combination in parents. Shoot length was reduced by 52.6% and root-shoot ratio was increased by 43.7% in 8 dSm-1 salinity while percent germination, shoot length, root length and root-shoot ratio were reduced by 9.6%, 53.9%, 66.7%, 27.2%, respectively, in response to 8 dSm-1 salt+0.1mM salicylic acid, compared to control. Salinity stress with salicylic acid reduced percent germination, root length, dry mass per plant and root-shoot ratio by 9.1, 58.6, 20.0 and 18.3 %, respectively, compared to salinity stress alone. These results indicated that salicylic acid in association with NaCl reinforced the severity of stress. Despite, a few genotypes showed notable tolerance against both salinity and dual stress indicating their potential to select for further breeding and QTL analyses. PC1 explained 38% variation and separated the genotypes under 8 dSm-1 salt+0.1mM salicylic acid treatment from two other treatments for high and positive coefficient for shoot length, percent germination, root length and root-shoot ratio suggesting those are salt responsive traits. The results offer a foundation for phenotypic selection, biochemical analysis, and future molecular analysis upon dual treatment of salicylic acid and salt. The results will be also useful for early identification and development of salt-resilient rapeseed lines through high resolution genetic mapping during further studies.