ROOTING AND ACCLIMATIZATION OF MICROPROPAGATED VITIS-LABRUSCA DELAWARE

Routine methods were developed to propagate through tissue culture large numbers of Vitis labrusca L. 'Delaware' cuttings on a 10-week production cycle. A 35-fold increase in shoots was achieved in 4 weeks through axillary bud proliferation of rejuvenated cultures using a modified Murashige and Skoog (MS) medium. Additive root-stimulating effects from the auxin combination of NAA at 0.001 mg . liter-1 and IBA at 0.005 mg . liter-1 in half-strength MS resulted in > 95% rooting of microcuttings in 10 days. More than 95% of the rooted plantlets were successfully acclimatized within 14 days using greenhouse flats fitted with humidity domes and containing a fortified soilless growing medium. Leaves from 21-day-old greenhouse plantlets lost 21% water after 40 min of holding at 40% relative humidity, compared to 62% from 9-day-old plantlets and 91% from 3-day-old plantlets. The combined features reported here enable clonal production of almost-equal-to 3000 'Delaware' grape plants per month using simplified methods and reduced intervals between sequential stages of development. Chemical names used: alpha-naphthaleneacetic acid (NAA), 1H-indole-3-butyric acid (IBA).