Identification of Intronless Genes and the Development of KASP Markers for Salt Responses in Vicia faba L

Background/Objectives: Salinity stress limits agricultural production and threatens global food security. Faba bean (Vicia faba L.) is an important legume crop, and identifying salt-stress-responsive genes may support an improvement in salt response. This study aimed to identify intronless genes in faba bean, screen candidate genes associated with salt-stress responses, and develop a KASP marker for salt-response evaluation. Methods: Intronless genes were identified from the faba bean reference genome. Transcriptome analysis was conducted in roots and leaves of two cultivars, Sucan 4 and Yundou 1183, under 150 mM NaCl treatment and control conditions. Candidate genes were examined by expression analysis, functional annotation, PPI prediction, and a luciferase complementation assay. A KASP marker was developed from an SNP within the VfERF1A locus and tested in 97 accessions. Results: A total of 7581 intronless genes were identified, accounting for 20.69% of annotated genes. Fifteen intronless genes were significantly differentially expressed in both roots and leaves of the two cultivars under salt treatment. Functional annotation suggested that VfERF1A and VfHSP17.8 may be involved in salt-stress responses. PPI prediction and the LUC assay provided preliminary support for a possible association of VfERF1A with VfEIN2. The VfERF1A-based KASP marker showed clear genotype clustering, and the two homozygous classes differed significantly in QYmax, relative shoot fresh weight, and relative plant height under salt treatment (p < 0.05). The preliminary predictive accuracy for QYmax was 86.36%. Conclusions: These results provide a genome-wide resource of intronless genes in faba bean, identify candidate genes associated with salt-stress responses, and describe a preliminary KASP marker associated with salt-response traits. Further validation in independent populations, under diverse environmental conditions, and with additional functional evidence is still required.