Establishing an Optimized EMS Mutagenesis Protocol for Tagetes erecta cv. Pusa Narangi Gainda: A Dose-Response Analysis in the M 1 Generation

The improvement of novel marigold ( Tagetes erecta L.) cultivars with enhanced ornamental value is constrained by limited genetic variability. Induced mutagenesis using ethyl methanesulfonate (EMS) provide a strong tool to produce new attribute, but its employment in marigold remains hampered by the lack of standardized, protocols. For widely cultivated African marigold, consistent methods to balance mutation induction with standard plant viability are critically needed to enable efficient mutant screening. This study demonstrates an refined EMS mutagenesis protocol for the commercially important cultivar i.e. ‘Pusa Narangi Gainda’. The effects of six EMS concentrations (10–60 mM) and two treatment durations (6 and 8 h) was studied on M ₁ generation (germination, growth, flowering, lethality, and mutagenic parameters). Results showed a significant (P ≤ 0.05), effects on all vegetative and floral traits. Germination and plant architecture (height, spread) decreased gradually with increasing the concentration of EMS. The higher doses strongly restrained vegetative growth, an intermediate dose of 20–30 mM EMS for 6 hours was identified as optimal, creating a favorable mutation window. This treatment increased number of flower per plant to 86.33 (at 30 mM) over 81.33 in the control, while maintaining > 80% germination and acceptable plant architecture. The 6 hour duration was generally more effective than 8 hours for key traits such as flower number. Probit analysis showed an extrapolated LD₅₀ of 261.27 mM, while mutagenic effectiveness and efficiency were highest at lower concentrations (10–20 mM). We conclude that EMS mutagenesis in marigold is highly dose specific, with intermediate doses (20–30 mM) optimally balancing floral enhancement against vegetative reduction. The known protocol gave a valid, reproducible framework for creating mutant populations in this cultivar, establishing a critical foundation for forward genetic screening and applied mutation breeding in marigold.