Control of shoot-tip necrosis during Argylia radiata in vitro multiplication

Abstract Argylia radiata is an herbaceous perennial plant native to northern Chile and a representative species of the “Blooming Desert”. Due to its showy flowers and other morphological characteristics, A. radiata has great ornamental potential. In earlier work, a deep morpho-anatomical description was made, but the micropropagation protocols, which could be used for commercial purposes, are not known. Previous assays showed that cytokinin supplementation improves the multiplication rate but produces shoot-tip necrosis in the microplants. To avoid it, different modifications of the growth medium were tested, including calcium nitrate supplementation; increasing in agar concentration; indole-3-butyric acid enrichment; and change of the basal medium formulation. The effect of these changes over the damage level, number of shoots, multiplication rate, plant height (cm), fresh weight and dry weight (g), and water content (%) of the microplants were evaluated. The use of McCown Woody Plant formulation as basal medium showed the best effect, reducing the damage level and improving the multiplication rate. Additionally, IBA supplementation was effective in reducing necrotic damage. However, 0.1 mg L-1 of IBA significantly decreased the multiplication rate, while 0.01 mg L-1 led to a higher multiplication rate than that of plants grown in the control medium. In conclusion, the use of McCown Woody Plant medium and IBA supplementation should be considered in commercial A. radiata micropropagation.