| Abstract: | Micropropagation of a mature ash tree has been achieved forthe first time. The main obstacle encountered was contaminationof the initial explants with microorganisms. However, once apparentlysterile shoots had been obtained, shoot proliferation was achievedmost effectively by culturing nodes on Driver and Kuniyuki walnutmedium containing 22.2 µM benzyladenine. After severalsubcultures, a species of Bacillus appeared with the matureculture line, but it did not affect shoot or root developmentadversely. With successive subculturing, shoots of the matureash clone became progressively easier to root. Pinnately compoundleaf explants from micropropagated shoots of two seedlings andthe mature tree, placed on to Murashige and Skoog-based culturemedia supplemented with 4.4µM-phenyl-N-1,2,3-thiadiazol-5-ylurea,produced shoot buds. Most buds developed from the rachis atthe points of attachment of the leaflets. When transferred toDriver and Kuniyuki walnut medium, buds from one of the seedlinglines and from the mature tree, elongated into shoots, and weresubsequently transferred to media for micropropagation and rooting.Shoot initiation is discussed in relation to possible occurrenceof vestigial meristems in the axils of leaflets and the partialshoot theory of leaf structure. Key words: Forestry, leaf structure, partial shoot theory, thidiazuron, tree |
