MICROPROPAGATION OF THE COLD-HARDY APPLE ROOTSTOCK KSC-3: A MORPHOLOGICAL ANALYSIS

Abstract

The cold-hardy apple rootstock KSC-3 (Malus × domestica Borkh.) was micropropagated on modified Murashige and Skoog (MS) medium using single node explants as the starting material. Explants grown on media containing BAP (0.5–5.0 mg L−1) and zeatin (5.0 mg L−1) produced multiple shoots. The largest number of shoots (≥ 5.0 mm) were obtained with 1.0 mg L−1 BAP. On the basis of useable shoots (≥ 15.0 mm), however, there was no difference in shoot number between 0.5 and 1.0 mg L−1 BAP. With increasing BAP concentration, shoot length decreased, while stem diameter increased. The longest shoots were obtained with 5.0 mg L−1 zeatin. Rooting was achieved by culturing individual shoots on either full or 1/4 strength MS. Reducing the MS concentration in the absence of exogenous auxin increased the percentage of rooted shoots and the median number of roots/shoot. When auxins were present, reducing the MS concentration had little effect on rooting. NAA, IBA and IAA were effective in promoting root formation while 2,4-D was often inhibitory. Basal callus formation increased when auxins were added to the rooting medium. The presence of 2,4-D or a reduction of the MS concentration to 1/4 strength had a detrimental effect on the shoots.Key words: Micropropagation, KSC-3, Malus, morphology, appleAbbreviations: MS = mineral salts of Murashige and Skoog (1962); BAP = 6-benzylaminopurine; 2iP = N6-(2-isopentyl) adenine; zeatin = 4-hydroxy-3-methyl-trans-2-butenylaminopurine; 2,4-D = 2.4-dichlorophenoxyacetic acid; NAA = 1-naphthaleneacetic acid; IBA = indole-3-butyric acid; IAA = Indole-3-acetic acid.