2017 ASHS Annual Conference

Plant propagation methods are foundational to agricultural and ornamental plant production sectors. In an attempt to optimize light quality conditions for coleus vegetative cutting propagation, seven commercial cultivars were selected for an initial screen: ‘Abbey Road’, ‘Lime Time’, ‘Limon Blush’, ‘Oxford Street’, ‘Velveteen’, ‘Trusty Rusty’, and ‘Twist and Twirl’. Narrow-bandwidth red light treatment improved root development of coleus cuttings in soil leading to increases in both shoot and root dry mass. Red light also enhanced root and shoot development in coleus ‘Gator Glory’ shoot tip cultures in vitro. When the cuttings in the soil were exposed to green light, the lowest growth parameters were observed. However, the shoot tips cultured in MS agar medium under green light showed better root and shoot growth than those of control (CWF) and blue light treatment. When the green light and red light were combined there were significant increases in root length, leaf and petiole length, dry weight and intermodal length compared to red light treatment alone. These results indicate the combination of red and green light could be the optimal light quality for coleus shoot tip culture in vitro. Blue light was not an ideal wavelength for propagation using shoot tip culture in vitro because it resulted in dwarf and compact plants.