Optimization of high-frequency shoot regeneration across ten snapdragon varieties

Snapdragon (Antirrhinum majus L.) represents a commercially significant ornamental species . In this study, a shoot regeneration protocol was developed using hypocotyl explants from ten snapdragon varieties. The experimental materials included four cut flower varieties (Maryland Apple Blossom, Maryland True Pink, Maryland White, and Maryland Red) and six bedding varieties (Snapshot White, Snapshot Rose, Snapshot Yellow, Snapshot Pink, Twinny Peach, and Twinny Apple Blossom). To achieve consistent and high-frequency shoot regeneration, hypocotyl explants were cultured on media with different combinations of NAA (0.05, 0.1, and 0.2 mg.L-1), Zeatin (2 and 3 mg.L-1), and AgNO3 (4 mg.L-1). Across six varieties, the combination of 0.05 mg.L-1 NAA, 3 mg.L-1 Zeatin, and 4.0 mg.L-1 AgNO3 resulted in 100% shoot regeneration efficacy and the highest number of shoots per explant. However, three bedding varieties (Snapshot Rose, Snapshot Yellow, Snapshot Pink) consistently exhibited low shoot numbers per explant across all tested media combinations. Therefore, to improve the regeneration rate and shoot number, explants from these varieties were further cultured on media containing 0.05 mg.L-1 NAA, 2 mg.L-1 Zeatin, and different concentrations of AgNO3 (0, 1, 2, 3, and 4 mg.L-1). Interestingly, the absence of AgNO3 produced the highest shoot numbers per explant and achieved 100% shoot regeneration frequency. The effect of AgNO3 on shoot regeneration varied among varieties, acting as either a positive or a negative regulator. Among the four combinations of rooting media tested, the Maryland White variety showed enhanced rooting in the absence of NAA. Conversely, Snapshot White (0.5 mg.L-1 NAA) and Twinny Peach (0.1 mg.L-1 NAA) demonstrated improved rooting with NAA supplementation.