Developmental Stage‐Dependent Gene Expression Modulates Maternal Control of Seed Vicine Biosynthesis in Faba Bean

ABSTRACT Faba bean ( Vicia faba L.) is a multipurpose legume valued for its high seed protein content and contribution to sustainable agriculture. However, its broader utilization is constrained by the presence of vicine and convicine (v‐c), antinutritional compounds distributed throughout the plant. Although key genes involved in v‐c biosynthesis have been identified, enabling genomic tools for breeding low v‐c cultivars, the biosynthesis and accumulation of v‐c within the plant remain incompletely understood. While previous studies reported maternal determination of seed v‐c content, the underlying molecular mechanism remains unclear. In this study, we used multiple reciprocal crosses between five high and two low v‐c parental lines to show that seed v‐c content is determined by the maternal genotype, with F1 seeds consistently reflecting the maternal v‐c phenotype. Expression analysis of VICINE‐CONVICINE 1 and RIBOFLAVIN BIOSYNTHESIS PROTEIN 2 revealed maternal influence, with transcripts predominantly expressed in the seed coat, while the embryo remained transcriptionally inactive. Tissue‐specific expression profiling confirmed that the activity of v‐c‐related genes is restricted to maternal tissues during seed development, suggesting that maternal determination is regulated by developmental stage‐specific transcription. This absence of gene activity in the embryo explains the observed phenotypic delay in which the seed v‐c content reflects the genotype of the previous generation. Despite maternal control of v‐c expression, we found that segregation of the v‐c trait follows Mendelian ratios regardless of cross direction, indicating that maternal phenotype does not affect breeding outcomes. These findings provide a molecular basis for maternal inheritance of v‐c content and offer practical insights for breeding strategies, including seed‐based genotyping, marker‐assisted selection, and hybrid or synthetic breeding, supporting effective development of low v‐c varieties.