Optimization of explant sterilization and plant growth regulators for enhancing the in vitro propagation of Nymphaea colorata Peter

Thailand is renowned as a key player in the global waterlily hybrid market, producing a diverse range of tropical waterlily hybrids year-round. To meet the growing global demand and address the limitations of traditional propagation methods, while ensuring high-quality plantlet production, in vitro propagation has emerged as a promising solution for ornamental waterlilies production. Nymphaea colorata Peter, a valuable waterlily species with multiple uses and close evolutionary ties to other species in the Nymphaeaceae family, was selected as the model plant for this study. High microbial contamination rates and low healthy shoot multiplication remain major obstacles in waterlily in vitro propagation. Therefore, this study highlighted on HgCl₂ sterilization treatments and plant growth regulators (PGRs) for shoot multiplication. In this study, turions were collected from mature rhizomes and subjected to soaking in 0.1% HgCl 2 (w/v) for 15 min effectively reducing microbial contamination, resulting in a 10% contamination rate with a 90% survival rate, and explant germination occurred within 5.70 days. Each explant produced 2 shoots, which remained healthy after culture in liquid MS medium for 4 weeks. The maximum shoot number (4.40 shoots/explant) with vigorous and lush leaves was observed in liquid MS medium fortified with 2.0 mg L − 1 BAP within 2 weeks of culture. The excised individual shoots were inoculated on semi-solid MS medium fortified with 0.5 mg L − 1 NAA, exhibiting the highest rooting response (80%) with a high number of roots (6 roots/shoot) and longest root length (3.82 cm), providing a strong root system. The plantlets achieved an 85% survival rate after transplantation into aquatic plant soil, followed by loamy clay soil under field conditions, showing robust growth and flowering in five weeks.