Author : Meman, Micah Abegail C.

Summary : Abiotic stresses, particularly salinity, are increasingly threatening rice production by reducing productivity and quality. CSSLs (Chromosome Segment Substitution Lines) offer a precise method for integrating beneficial genes from donor parents into elite cultivars, enabling targeted improvements in stress tolerance. This study focuses on developing CSSLs to enhance salinity tolerance by incorporating traits from Oryza glaberrima and Gundang, a traditional Philippine rice variety. The two populations comprised of 76 CSSL entries from QD49 and IRGC population, were backcrossed to gradually replace the recipient's chromosomes with donor segments, resulting in a set of lines representing overlapping donor genomes. Using the IK RiCa SNP genotyping platform, chromosomal positions of substituted segments were identified. A total of 463 SNP markers were distributed across 12 chromosomes, with significant substitutions on Chromosomes 1, 3, 5, and 7 for QD49, and Chromosomes 1, 2, and 7 for the IRGC population. Candidate CSSLs underwent initial and validation salinity screenings under 50 mM and 150 mM NaCl. Eleven CSSLs exhibited a nine to ten days delay in progressing to SES 4 were selected in the initial screening, indicating potential salinity tolerance. The validation screening under 50 mM and 150 mM NaCl confirmed the variability observed in the selected CSSLs, suggesting multiple genes with complex interactions contributing to tolerance. The variability in tolerance observed suggests complex gene interactions. The result of this study can be further evaluated through fine mapping to identify the genomic regions responsible for salinity tolerance.