Fine Mapping of the QTL qRLP12 That Controls Root Length Under Polyethylene glycol-Induced Drought Stress During the Early Seedling Stage of Sesame

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) <i>qRLP12</i> 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 <i>qRLP12</i> to a 91 kb region. Seven putative predicted genes were identified in the target region, among which <i>LOC105165547</i>, 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 <i>LOC105165547</i> was significantly induced by PEG stress in the <i>qRLP12</i>+ line. These indicated that <i>LOC105165547</i> might be the candidate gene for <i>qRLP12</i>, 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.