Marker-Assisted Breeding for Salt Tolerance in Rice: In Bangladesh Context.

Rifat Hasan Rabbi

Salinity stress threatens rice (Oryza sativa L.) production across 1.056 million hectares of Bangladesh's coastal regions, with intensification projected due to climate change and sea-level rise. Marker-assisted breeding (MAB) has emerged as a transformative approach for developing salt-tolerant varieties, offering precision and efficiency over conventional methods. This review examines marker-assisted selection (MAS) and marker-assisted backcrossing (MABC) applications for salt tolerance improvement in Bangladesh's rice breeding programs. We analyze the genetic architecture of salt tolerance, particularly the major Saltol QTL harboring OsHKT1;5 on chromosome 1, and discuss molecular marker systems including SSRs, SNPs, and InDels utilized by the Bangladesh Rice Research Institute (BRRI). The review documents successful introgression of salt tolerance into elite varieties, resulting in seventeen released varieties including BRRI dhan47, BRRI dhan73, and BRRI dhan78, with yields of 4.5-8.3 t ha⁻¹ under saline conditions (8-14 dS m⁻¹). We evaluate physiological mechanisms of Na⁺ exclusion and ionic homeostasis, analyze breeding achievements using foreground and background selection strategies, and discuss future integration of genomic selection, GWAS, and CRISPR/Cas9 gene editing. Despite substantial progress, continued integration of molecular breeding with phenomics and participatory approaches remains essential for developing climate-resilient varieties addressing Bangladesh's intensifying salinity challenge.