Genetic variation, trait association and heritability of root traits in parental and hybrid Brassica napus genotypes under PEG-treated hydroponic culture

Background: Rapeseed ( Brassica napus L.) is an important oilseed crop susceptible to drought stress. Research on rapeseed root systems is limited. This study aimed to determine the effects of Polyethylene Glycol (PEG)-induced osmotic stress in selected rapeseed breeding lines and hybrids, particularly on the root morphology. Methodology: Plants were cultured hydroponically for 25 days and subjected to two PEG concentrations: 0 (control) and 5%. Two weeks later, nine root traits, five shoot traits, and four biochemical traits were measured after a destructive harvest. Results: PEG-induced osmotic stress enhanced root dry weight by producing long and thick main and lateral roots and longer root hairs while suppressing the morphological growth of shoots. A negative association among root and shoot traits was found from principal component analysis. PEG treatment also altered the synthesis of antioxidants and reactive oxygen species. There was a trait-specific genotypic response to the two PEG levels. Among the root traits, lateral root length, root hair length, and root dry weight accounted for high variability and heritability. Conclusion: Root traits showing high heritability can be selected for advancing generations to select rapeseed genotypes with osmotic stress-tolerant root systems. The results imply that rapeseed breeders may consider lateral root traits in drought-stress breeding.