Chemical mutagenesis is an important approach in rice (Oryza sativa L.) improvement, as it can develop novel genetic variation for breeding programs. Sodium azide (SA) is one of the most effective chemical mutagens used in cereals; however, information on the sensitivity of Indonesian salt-tolerant rice cultivars to SA remains limited. This study aimed to determine the LD₅₀ values of SA in two salt-tolerant cultivars (Biosalin-1-Agritan and Biosalin-2-Agritan) and one high-yielding cultivar (Inpari 32 HDB). Three rice cultivars sustained exposure to varying SA doses, examining their germination traits, seedling vigor, and their survival responses through median lethal doses (LD₅₀) values. The results revealed distinct genotype-dependent responses. The rice cultivars Biosalin-1-Agritan and Biosalin-2-Agritan emerged with LD₅₀ values of 8.30 and 9.20 mM, respectively, indicating moderate sensitivity to SA. In contrast, cultivar Inpari 32 HDB demonstrated the highest tolerance with LD₅₀ (17.00 mM) with better performance in germination, synchrony, and growth across the SA doses. The root and shoot growth showed inhibition in a dose-dependent manner in all rice genotypes; however, the extent of inhibition was more severe in the Biosalin cultivars, particularly with doses of ≥6 mM. The rice genotypes screening provides a considerable baseline before chemical mutagenesis through SA doses in rice breeding programs.

Keywords: Rice (O. sativa L.), mutagenesis, sodium azide, screening, sensitivity, seed viability, seed vigor

Key findings: This study identified genotype-specific responses to sodium azide in rice (O. sativa L.), revealing salt-tolerant cultivars were more sensitive to chemical mutagenesis than a popular high-yielding cultivar. The LD₅₀ values provide critical baseline data for optimizing mutagenesis protocols in rice breeding programs.