Development of the First Integrated Silver Nitrate-Containing In Vitro Regeneration Approach for the Endangered Tulipa montana var. chrysantha

Tulipa montana Lindl. var. chrysantha (Boiss.) Wendelbo is a native Iranian tulip occurring in the highlands of the Alborz Mountains. This study aimed to establish an efficient in vitro regeneration protocol by optimizing explant disinfection, bulblet regeneration, and rooting conditions. Basal and distal bulb-scale, leaf, petal, and flowering-stem explants were evaluated using different sodium hypochlorite (NaOCl) exposure times and silver nitrate (AgNO3) concentrations. AgNO3 concentrations of 0, 100, 200, and 300 mg L−1 were tested during establishment; 300 mg L−1 resulted in the lowest contamination and was subsequently retained during regeneration. Leaf, petal, and flowering-stem explants did not regenerate, whereas bulb-scale explants produced regenerated bulblets. Combinations of 6-benzylaminopurine (BAP) or thidiazuron (TDZ) with 1-naphthaleneacetic acid (NAA) were evaluated. The highest number of regenerated bulblets was obtained with 2 mg L−1 TDZ + 1 mg L−1 NAA, while the greatest shoot length occurred with 1 mg L−1 TDZ + 1 mg L−1 NAA. The highest root number was obtained on ½ MS + 1 mg L−1 NAA, whereas the longest roots developed on ½ MS + 0.5 mg L−1 NAA. Approximately 80% of plantlets survived after one month of acclimatization.