Facilitation of microshoot tip propagation of Vitis aestivalis var. Norton by combined application of an antioxidant and cytokinins

The Vitis aestivalis Michx.-dervied grape variety Norton proved to be recalcitrant to in vitro microshoot tip propagation under tissue culture conditions that were devised for Vitis vinifera L. In this study, various cytokinins, antioxidants, and nutrient salt concentrations were tested in an attempt to improve the viability and growth of V aestivalis var. Norton shoot tips in vitro. Incorporation of the antioxidant dithiothreitol at a concentration of 5 mg/L into a solid, single-layer medium remarkably increased the viability of V aestivalis microshoot tips. The presence of 6-benzylaminopurine or zeatin riboside at a concentration of 2 mg/L induced the growth of V aestivalis microshoot tips, but a combination of zeatin riboside at 2 mg/L and 6-benzylaminopurine at 0.5 mg/L slightly improved the microshoot tip growth. In contrast, heat treatment of the source vines or the concentration of nutrient salts in the medium had little or no effect on the viability or growth of shoot tips. These findings suggest that microshoot tip propagation in recalcitrant Vitis genotypes can be improved significantly by adjusting the components of the culture medium.