Morpho-physiochemical traits and metabolic analysis reveal the rapeseed responses under large clod sized soil conditions

Abstract

Soil clod size is an important factor affecting seedling growth; besides, cultivation of strong seedlings is important to improve yield and benefit of direct-seeding rapeseed. To simulate the open field conditions, two rapeseed cultivars were grown in different clod sized soil to study morpho-physiochemical responses at five leaf stage, beside applying metabolite profiling. Moreover, foliar application via alpha-linolenic acid (ALA) was applied to improve the adaptability of rapeseed to large clod sized soil. Our results showed that soil water content was decreased in large clod sized soil (K2) versus small clod sized soil (K1), which decreased seedling weight, shoot length and root vitality, while increasing root length. Furthermore, osmolyte contents and peroxidase (POD) and catalase (CAT) activity were decreased with increasing malondialdehyde content in studied rapeseed cultivars under K2 conditions. Moreover, phospholipase A2 (PLA2) of phospholipid metabolism and its related enzymes were decreased, while its content and gene expression were increased. Besides, ALA metabolism was up-regulated, while lipoxygenase (LOX) activity, content and its gene expression were elevated under K2 conditions. Metabolic profiling showed that lipid metabolism was significantly changed than other identified components, which is synthetic precursors of various secondary metabolites. Compared with K1, the metabolic pathways of ALA and pyrimidine were up-regulated, while the metabolic pathways of glycerophospholipids and purines were down-regulated in both studied cultivars under K2 conditions. Moreover, ALA application enhanced seedling growth by improving root length, shoot and root dry weight, root vitality, ALA and proline contents, while reducing the malondialdehyde (MDA) content of two rapeseed cultivars under K2 conditions. Taken together, our study provided a theoretical basis and technical support for the soil tillage and cultivation of direct-seeding rapeseed.