Dormant canes of `Muscat Bailey A´ (MBA) and `Riesling´ grapes were collected on November 1, and received various chilling at 4℃ for 0, 4, 8, and 10 weeks, and the percent bud break was examined at 25℃. The shoots derived from the cuttings were divided into shoot tips and axillary bud segments, and cultured separately in vitro on Murashige and Skoog´s (MS) medium supplemented with BAP, GA, NAA, and Picloram, and their responses in shoot growth, callus formation, branching, and rooting were studied.
1. Percent bud break of MBA was higher than that of `Riesling.´
2. Percent bud break of both cultivars increased with the additional chilling, showing the peak percent bud break with 10 weeks´ chilling at 4℃, but percentage of buds grown over 5㎝ was highest with 8 weeks´ chilling.
3. Increase in shoot growth of `Riesling´ by prolonged chilling was recognized only when eaplants were grown on basal and 1 μM BA-supplemented MS medium.
4. Shoot growth of `Riesling´ explants grown on basal VIS medium was better than that of MB a, but the difference was diminished by the supplementation of plant growth regulators. There also was no difference between shoot tips and axillary bud segments in growth performance.
5. IAA (2.7, 10.7μM) and Picloram (2.5, 10.0μM) enhanced the rate of callus proliferation of two cultivars, and calli induced by NAA and Pieloram covered the whole explants soon after inoculation. When NAA was supplemented to MS medium, shoots and roots were developed from the explants covered with callus, but Ficloram-induced mass of callus were browned and eventually died.
6. BAP (2.2, 4.4μM) enhanced the branching, and the growth of resulting lateral shoots was normal in both cultivars.
7. `Riesling´ rooted better than MBA, and NAA at 2.2 and 10.7μM increased the rooting of two cultivars. The straight, thick, and long roots were developed from MBA explants, while `Riesling´ resulted in many thin rootlets.
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