Silver Nanoparticles As the Sterilant in Large-Scale Micropropagation of Chrysanthemum

Micropropagation has proven to be an effective method for large-scale plant production in a short time and a useful tool for plant breeding. Microbial contamination is one of the most difficult micropropagation challenges, resulting in reduced plant quality and loss of valuable stocks. Therefore, sterilization of culture media is a critical step in plant micropropagation. However, sterilized media might reduce the activity of plant growth regulators and nutritional components of culture media. The sterilization effects of silver nanoparticles (AgNP) on the growth of explants and culture media were examined. The treatment with 250 ppm AgNP for 15 to 20 min of 4-wk-old ex vitro leaves proved optimal for controlling the contamination. Furthermore, the Murashige and Skoog medium containing 4 ppm AgNP resulted in 100% medium disinfection (no contamination) after 4 wk of culture. The plantlets obtained from non-sterilized MS medium (NoM) containing 4 ppm AgNP and 4 g L −1 agar gave similar results as the control medium with 8 g L −1 agar and the absence of AgNP. Large scale culture systems using NoM in large plastic containers of two different sizes (NoM1 and NoM2) could produce quality plantlets. Chrysanthemum plantlets in the NoM1 system showed higher antioxidant enzyme activities of ascorbate peroxidase and superoxide dismutase than plantlets in the autoclaved medium. Furthermore, the plantlets from NoM were better acclimatized under greenhouse conditions than those from the autoclaved medium (AuM) system. The developmental stages (flower buds and blooming time) of NoM1 and NoM2 plantlets, were 1 wk earlier than those from the AuM system. The successful use of AgNP as a sterilizer and as a component of culture media would reduce the cost of micropropagation and improve plants' quality.