Aimed at determining the effects of topping and various concentrations of ethephon on production traits of rapeseed (Brassica napus L.), the latest research proceeded during the winter of 2022–2023 at the University of Basrah, Iraq (30° 57ʹ N latitude, 47° 80ʹ longitude). The experiment layout was in a randomized complete block design, with two factors and three replications according to split plot arrangement. The topping and ethephon occupied the main plots, with symbols as T = topping, E0 = zero ethephon concentration, E1 = 1 ml L^-1 ethephon, and E2 = 2 ml L^-1 ethephon. The subplots comprised crop development and growth stages (elongation, flowering, and branching) represented by the symbols S1, S2, and S3. The evaluated traits consisted of plant height (cm), number of branches (branches m^-2), leaf area (cm²), pods per plant (pods plant^-1), seeds per pod (seeds pod^-1), 1000-seed weight (g), seed yield per plant (g plant^-1), and harvest index (%). The findings indicated ethephon concentrations and topping significantly differed for most traits. The ethephon with concentration of 2 ml L^-1 showed the highest seed yield (21.38 g plant^-1); however, it has a nonsignificant difference from the topping treatment (20.75 g plant^-1). The study showed that spraying at various growth stages had relevant effects on most studied features, and the S1 stage gave remarkable results, with the maximum seed yield (19.26 g plant^-1). The combination of spraying ethephon (E2, 2 ml L^-1) at the S1 stage had the best results, exhibiting the premier grain yield (24.03 g plant^-1). However, the said treatment was at par with the topping treatment at the same growth stage (23.44 g plant-1).

Keywords: Rapeseed (B. napus L.), ethephon, topping, growth stages, production, morphological and yield traits

Key findings: The rapeseed (B. napus L.) best performed with topping and foliar application of ethephon at 2 mL/L, giving the highest yield of 21.38 and 20.75 g/plant. The topping and spraying had better results for most traits assessed, including plant yield during the elongation stage (S1).