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) 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.