Pathway Control and Breeding Strategies for Erucic Acid in <i>Brassica</i> Oilseeds (Rapeseed–Mustard): A Review

ABSTRACT Erucic acid (EA; 22:1) lies at the intersection of food safety, industrial chemistry and plant breeding, because regulations continue to restrict its concentration in edible oils while demand remains strong for renewable long‐chain fatty acids in lubricants, polymers and related specialty products. In oilseed crops, EA accumulation depends on the efficiency of fatty‐acid elongation from oleic acid, the strength of competing desaturation pathways and the broader metabolic context of developing seeds. These processes are further influenced by environmental conditions, particularly temperature and water availability during seed filling, which can generate substantial genotype × environment effects on final EA content. From a breeding perspective, low‐erucic cultivars represent a major historical success in quality improvement, whereas the development and stabilization of high‐erucic genotypes remain a more demanding challenge because industrial use requires consistently high EA levels together with acceptable oil content and agronomic performance. Here, we review the molecular, genetic and agronomic control of EA in oilseed crops and show how this knowledge can support more effective breeding strategies. The interest of this review lies in bringing together evidence that is often dispersed across biochemistry, genomics, physiology and applied breeding, thereby providing a clearer framework for the improvement of both established low‐erucic backgrounds and, more importantly, high‐erucic industrial materials. The major points are that EA accumulation is primarily determined by the FAE1‐encoded elongase, that transcriptional regulation and metabolic flux further shape substrate allocation to very‐long‐chain fatty acids, that environmental modulation is especially important for the stable expression of HEAR phenotypes and that QTL analysis, marker‐assisted selection, gene editing and emerging predictive approaches now offer improved tools for the targeted breeding of oilseed ideotypes with contrasting end uses.