Propagation of Ornamental Plants
5(3): 164-169, 2005
BACTERIA DETECTION AND MICROPROPAGTION OF TEN BUDDLEIA CULTIVARS
Sinead Phelan1&2*, Alan Hunter2 and Gerry Douglas1
¹Teagasc Kinsealy Research Centre, Malahide Road, Dublin 17, Ireland. *Tel.:+353 1 8459000, Fax: +353 1 8460524, e-mail: firstname.lastname@example.org
² Department of Crop Science, Horticulture and Forestry, University College Dublin, Belfield, Dublin 4, Ireland
Nursery growers in Ireland and Europe, producing Buddleia by conventional cuttings, have reported that the plants produced suffer from apical dieback, a disorder that reduces plant quality. Micropropagation methods are currently being developed to combat the problem of apical dieback and rejuvenate plant growth of Buddleia cultivars. Shoots were excised from stock plants and established on a MS modified medium containing 0.22 µM BAP under standard micropropagation conditions. Bacterial contamination was most problematic for nodal cultures irrespective of whether single or two-node explants were cultured. Two-node explants for all cultivars of Buddleia produced higher micropropagation rates compared to those of single nodes and apical tips. In vitro flowering of shoot tips for five Buddleia cultivars was observed. Apical tips from proliferated shoots of four Buddleia cultivars were rooted on half-strength MS medium containing 19.7 µM IBA for four days, prior to transfer to MS without growth regulators. No significant difference was found among the rooting percentages, although the mean number of roots produced varied significantly. Survival of explants upon weaning was 100%. Conventional cuttings from stock plants (shoot tip and one node) were treated with SeradixТ 3 rooting powder ex vitro. All cultivars exhibited 100% rooting. Bacteria were detected by culturing internodal explants on Tryptic Soy Broth (TSB) and were found in cuttings from stock plants, shoots from plants cultured in vitro and in plants weaned to the greenhouse from shoot cultures. Pure colonies for each bacteria isolate detected were obtained and grouped based on color and colony morphology. At least two different isolates were detected for each cultivar. This confirms that although shoot cultures appeared free from bacteria, the bacteria presence could be confirmed using TSB..
Key words: Buddleia davidii, Buddleia cv. Lochinch, 2-node explants, endogenous bacteria, micropropagation, tryptic soy broth