Effect of foliar-applied brassinosteroid on morphological traits, seed yield, and growth indices of camelina (Camelina sativa) under salinity stress

Introduction
Salinity stress significantly impairs plant growth and yield and represents a major challenge to sustainable agriculture. Camelina (Camelina sativa), an oilseed crop, is well known for its resilience to adverse environmental conditions, including salinity. Brassinosteroids, as plant growth regulators, have shown potential to mitigate salinity-induced stress. This study evaluated the effects of foliar brassinosteroid application on morphological traits, seed yield, and growth indices of camelina under salinity stress, with the aim of identifying effective strategies to improve crop performance in saline environments.
 
Materials and methods
A field experiment was conducted over two cropping seasons (2021–2022 and 2022–2023) in Yazd, Iran, using a split-plot arrangement in a randomized complete block design (RCBD) with three replications. Salinity levels (0, 4, 8, and 12 dS m⁻¹) were assigned to main plots, and foliar application of 24-epibrassinolide (0, 1, 2, and 3 μM) was assigned to subplots. Morphological traits (plant height, number of lateral branches, number of siliques per plant, and seeds per silique), yield components (thousand-seed weight and seed yield), and growth indices (biological yield and harvest index) were measured. Data were analyzed in SAS 9.1 using a mixed model, with year considered a random effect. Normality was assessed using the Kolmogorov–Smirnov test, and homogeneity of variance was evaluated using Bartlett’s test (χ² = 3.45, P = 0.32). A combined two‑year analysis was conducted, and treatment means were compared using the LSD test at the 5% significance level.
 
Results and discussion
The salinity × brassinosteroid interaction significantly affected all measured traits (P < 0.01). Salinity at 12 dS m⁻¹ reduced seed yield by 44% compared with untreated plants (0 μM) at 0 dS m⁻¹, whereas 3 μM brassinosteroid increased seed yield by 59%, 59%, 55%, and 76% at salinity levels of 0, 4, 8, and 12 dS m⁻¹, respectively, relative to untreated plants (0 μM) at the same salinity level (LSD = 85.3 kg ha ⁻¹). Plant height increased by 95%, 33%, 51%, and 50% at the respective salinity levels with 3 μM brassinosteroid, compared with untreated plants (LSD = 2.03 cm). The number of lateral branches increased by 161%, 23%, 97%, and 193% at salinity levels of 0, 4, 8, and 12 dS m^-1, respectively, with 3 μM brassinosteroid (LSD=1.16); however, the difference between 2 and 3 μM at 12 dS m⁻¹ was not significant (difference = 1.05 < LSD = 1.16). Leaf area index was not significantly affected by brassinosteroid treatments at any salinity level. (LSD = 0.12). The number of siliques per plant increased significantly, reaching up to 39% at 8  dS/m. Biological yield and harvest index at 12 dS m⁻¹ increased by 50% and 18%, respectively, relative to untreated plants (0 μM) (LSD = 150.2 kg ha⁻¹ and 1.45%). These findings are consistent with previous studies, suggesting that brassinosteroids can mitigate salinity stress by enhancing growth and reproductive traits (Sharma et al., 2022b; Khalid et al., 2020; Kaya et al., 2025).
 
Conclusion
Overall, salinity stress adversely affected camelina growth and yield; however, foliar application of 3 μM brassinosteroid effectively mitigated these effects and significantly improved morphological traits, seed yield, and growth indices. This treatment offers a promising strategy to improve camelina performance in saline environments and support sustainable agriculture in salt‑affected regions.