Mapping of a major QTL for salinity tolerance at the bud burst stage in rice (Oryza sativa L) using a high-density genetic map

Salinity tolerance plays an important role in direct seeding cultivation since tolerance to salinity at the bud burst stage of rice directly affects seedling formation and yield. However, information on the quantitative trait loci (QTL) associated with salinity tolerance at the bud burst stage is limited. Here, a recombinant inbred line (RIL) population, derived from a cross between Kongyu131 (salinity-sensitive) and Xiaobaijingzi (salinity-tolerant), was used to identify QTLs for salinity tolerance at the bud burst stage using a high-density genetic map. Four QTLs were identified. The threshold LOD score for QTL identification was 3.0. Among the four QTLs detected, two QTLs namely qRSL3 (PVE, 22.59%) and qRRL3 (PVE, 21.21%) were considered to be one QTL, named qST3, which was the major QTL related to salinity tolerance on chromosome 3. This major QTL was located within an interval of 2.55 Mb and contained 253 candidate genes. Using RNA-seq data, 51 differentially expressed genes (DEGs) were detected among the candidate region. According to Rice Annotation Project and quantitative real-time PCR (qRT-PCR) analysis, Os03g0664800 was accepted as the most likely candidate gene for qST3. These results will be useful for improving salinity tolerance of rice and for developing rice cultivars suitable for direct seeding in salinized soil.