A deeper root system can improve the efficiency of water and nutrient absorption from soil; therefore, genetic improvements to the root length of crops are essential for yield stability under drought stress. We previously identified a stable quantitative trait locus (QTL) qRLP12 for root length under polyethylene glycol (PEG)-induced drought stress in a Jinhuangma (JHM, sensitive)/Zhushanbai (ZSB, tolerant) recombinant inbred line (RIL) population. To validate and fine map this QTL, in this study, a secondary F₂ population was constructed, and the genetic effect of the target QTL was validated by comparing the phenotype data of different genotypes. Using newly developed markers, 14 genotypes of recombinant F₂ individuals were obtained. A phenotypic analysis of homozygous recombinant progeny lines narrowed qRLP12 to a 91 kb region. Seven putative predicted genes were identified in the target region, among which LOC105165547, a callose synthase gene, was the only one containing nonsynonymous variations in the coding region between two parents. Quantitative real-time PCR analysis revealed that LOC105165547 was significantly induced by PEG stress in the qRLP12+ line. These indicated that LOC105165547 might be the candidate gene for qRLP12, which is responsible for root length subjected to PEG stress. Our results provide a favored gene resource for improving root length under drought stress in sesame.

Auxin response factors (ARFs) are pivotal regulators mediating plant growth, development, and abiotic stress responses, especially during seed germination under stressful conditions. However, the ARF gene family has not been thoroughly studied or characterized in sesame. The identification and characterization of ARF family members in the sesame genome were analyzed by bioinformatics methods, and the expression patterns of sesame ARF genes were assessed by quantitative real-time PCR. In this study, a total of 23 ARF genes were identified in the sesame genome, distributed unevenly across 12 chromosomes. Additionally, 15 segmental duplication events were detected. Phylogenetic analysis classified the SiARF genes into four subfamilies, with members within each subgroup sharing conserved structural features and motif compositions. Promoter analysis revealed multiple cis-acting elements associated with plant growth, phytohormone responses, and stress responses. Expression profiling demonstrated distinct tissue-specific expression patterns among the SiARF genes. Notably, SiARF5 and SiARF15 showed predominant expression in seeds 5 days after pollination, whereas SiARF14 exhibited broad expression in roots, stems, leaves, and seeds germinated for 24 h. QRT-PCR analysis identified eight SiARF genes exhibiting biphasic expression patterns during seed germination under abiotic stresses, characterized by initial downregulation and subsequent upregulation. Among them, SiARF11 showed significant induction under all three stress conditions, while SiARF9 was specifically upregulated under salt stress, suggesting their critical roles in stress response regulation. These findings provide a foundation for further investigation into Auxin-mediated responses to abiotic stress during seed germination in sesame.