Optimized Micropropagation of Rosa indica L. via BAP–IAA Synergy and Hormone-Free Rooting

Conventional propagation of Rosa indica L. through stem cuttings is limited by low rooting efficiency and seasonal dependence, restricting large-scale production. This study aimed to develop a simplified and cost-effective micropropagation protocol by optimizing cytokinin–auxin interactions for shoot multiplication, assessing the need for exogenous auxins during rooting, quantifying multiplication efficiency and examining In vitro flowering. Single-node explants from field-grown clonal mother plants were cultured on Murashige and Skoog (MS) medium supplemented with combinations of 6-benzylaminopurine (BAP) and auxins. The experiment followed a completely randomized design (CRD) (n = 60 per treatment) and data were analyzed using ANOVA and LSD at p < 0.05. The combination of 3 mg L⁻¹ BAP + 3 mg L⁻¹ indole-3-acetic acid (IAA) produced the best results, with the highest shoot proliferation (3.55 ± 0.15 shoots per explant), longest shoots (4.72 ± 0.12 cm) and fastest initiation (17.77 ± 0.33 days). The multiplication rate was 3.55 shoots per explant per 30-day cycle, yielding approximately 12.6 shoots after two cycles. For rooting, micro shoots were transferred to half-strength MS media with or without auxins. Half-strength MS without growth regulators showed superior rooting (4.67 ± 0.09 roots per shoot; 2.60 ± 0.07 cm), significantly outperforming auxin-supplemented media. In vitro flowering occurred in 8.3% of cultures after 8 weeks on BAP–IAA medium, representing a novel observation under simplified conditions. Somaclonal variation increased with subcultures, reaching 21.7% after four cycles. The optimized low-input protocol enables year-round mass propagation of Rosa indica, giving nurseries a practical way to avoid seasonal dependence and lower input costs for plant growth regulators.