Sodium azide-induced mutagenesis and molecular characterization of banana mutants for enhanced drought tolerance under PEG-induced osmotic stress

The development of drought-tolerant genotypes is essential for sustainable banana production in the face of climate changes. This study utilized chemical mutagenesis via sodium azide (NaN3) at varying concentrations (0.002M, 0.004M, and 0.008M) and exposure durations (20 and 30 minutes) to induce genetic variation in three banana cultivars: ‘Grand Nain’, ‘Rahan 17’, and ‘Ra’. Resulting mutants were screened for drought resilience under PEG-induced osmotic stress (0%, 5%, 10%) at the rooting stage. Low-to-moderate treatments (T1-T4) enhanced shoot morphology in ‘Grand Nain’ and ‘Rahan 17’, while ‘Ra’ performed optimally under T1-T2. Conversely, higher concentrations (T5-T6) consistently inhibited growth across all cultivars. Under 5% PEG stress, mutants from T1, T3, and T4 showed superior growth, while T1, T2, T3, and T6 surpassed control groups at 10% PEG. Physiological analysis revealed significantly higher proline accumulation in specific lines, notably T1, T2, and T5 in ‘Grand Nain’; T2 and T3 in ‘Rahan 17’; and T1 and T2 in ‘Ra’. Genetic polymorphism, assessed using ISSR markers, reached 63.04%. The highest genetic variation (31.68%) was identified in the ‘Grand Nain’ mutant resulted from T2+10%PEG, whereas the lowest (14.85%) occurred in ‘Rahan 17’ (T2+10%PEG) and ‘Ra’ (T1+10%PEG). These results indicate that the magnitude of genetic change is both genotype- and treatment-dependent, which is crucial for selecting stable, true-to-type mutant lines for commercial use. Ultimately, this study identifies specific NaN₃-induced mutants that combine vigorous growth with biochemical resilience, providing valuable germplasm for breeding climate-resilient bananas.