Optimization of Selected Minerals and a Cytokinin for In Vitro Propagation of Little-Leaf Mockorange (Philadelphus microphyllus A. Gray) Using Response Surface Methodology (RSM)

Abstract

Optimizing concentrations of minerals and phytohormones is essential when culturing a new plant species. The objective of this study was to use Response Surface Methodology (RSM) to evaluate combinations of selected minerals (N, Ca, and P) along with zeatin (Zea) to obtain optimum shoot growth of little-leaf mockorange. Forty-six treatment combinations were assigned using Proc Optex in SAS software version 9.4. The concentrations of Zea tested were 0.82, 1.095, or 1.37 µM, and the minerals were 22.5, 30, or 37.5 mM N, 1.13, 1.5, or 1.875 mM Ca, and 0.31, 0.625, or 0.937 mM P. Treatment concentrations were tested for their effects on the number of axillary shoots formed, shoot length, and dry weight. The response surface analyses showed that the optimum concentrations of N, Ca, and P were 34 to 39 mM, 1.5 mM, and 0.625 mM, respectively. Medium supplemented with 1.1 µM Zea affected shoot growth positively. Comparison of mineral concentrations in medium with concentrations in full-strength Murashige and Skoog (MS) medium, suggests ½ MS medium should be appropriate to efficiently multiply little-leaf mockorange shoots efficiently, thus saving the time and money involved in creating a custom medium formulation.