Cytokinins, donor plants and time in culture affect shoot regenerative capacity of American elm leaves

Abstract

Cytokinins, donor plants and their time in vitro as well as basal media were investigated for their influence on shoot regenerative capacity of American elm (Ulmus americana L.) leaves. Leaves excised from six 2-year-old seedlings formed adventitious shoots when placed on Driver and Kuniyuki Walnut (DKW) medium supplemented with 7.5, 15 or 22.5 laM of benzyladenine (BA) or thidiazuron (TDZ). Thidiazuron induced significantly higher regeneration percentages on elm leaves than BA, regardless of concentration used. Donor plant also affected the efficiency of shoot regeneration, with certain seedlings having 1.5 to 7 times more explants forming shoots as compared to other seedlings tested. By subculture 15, the average number of shoots per regenerating explant increased at least 3-fold for leaves on media with BA or TDZ for the one donor plant that survived continued subculturing. Leaf explants from donor plants with the highest regenerative capacity had a higher percentage of shoot formation on DKW than MS medium. Explants from productive donor plants should be placed on DKW medium supplemented with TDZ to improve shoot regeneration efficiency from American elm leaves.

Micropropagation of mature wych elm (Ulmus glabra Huds.)

“…In our experiments no fasciated shoots of wych elm were observed. Our results are consistent with those reported by George and Tripepi (1994) for U. americana where TDZ induced significantly higher shoot formation percentages than BAP. The mean number of American elm shoots per explant ranged from 3.1 shoots on 7.5 mM TDZ to 11.1 shoots on 22.5 mM TDZ.…”

“…Micropropagation techniques combine both the strategies of short-to-medium-term ex situ storage of valuable genotypes and bulky production of the clonal plant stock (George 1993). Adventitious shoot formation has been induced from nodal segments of mature U. pumila trees (Corchete et al 1993), on leaf explants of juvenile U. americana (Bolyard et al 1991;George and Tripepi 1994), an on strips of the woody stem of the Dutch elm hybrid 'Commelin' (Ben Jouira et al 1998). Krajňµkovµ and Longauer (1996) reported adventitious shoot multiplication in mature hybrid clones of U. pinnatoramosa and successful establishment of the regenerants in the field.…”

Somatic embryogenesis and plant regeneration from leaves of Ulmus minor Mill.

“…However, this strategy can only be initiated after the establishment of efficient protocols for plant regeneration from cells and tissues of elm trees (Fenning et al 1996a). Protocols of this type have already been developed from differentiated explants (Fink et al 1986;Dorion et al 1987;Bolyard et al 1991;Fenning et al 1993;George and Tripepi 1994;Cheng and Shi 1995;Kapaun and Cheng 1997;Ben Jouira et al 1998), from callus (Karnosky et al 1982), from suspension cultures (Durzan and Lopushansky 1975) and from protoplasts (Sticklen et al 1986;Dorion et al 1994) of some species and clones of special interest.…”

Thidiazuron induces shoot organogenesis at low concentrations and somatic embryogenesis at high concentrations on leaf and petiole explants of African violet (Saintpaulia ionantha Wendl.)

“…Regeneration via shoot organogenesis from various types of explants, including leaf discs, petioles, petals, and anthers, with plant growth regulators such as IAA, NAA, BA and kinetin have been described in African violets (Bilkey and Cocking 1981;Harney and Knop 1979;Lo 1997;Start and Cumming 1976;Vazquez et al 1977). In a number of plant species, the in vitro morphogenic response is influenced considerably by the type of explant (Brand and Lineberger 1992;George and Tripepi 1994;Leege and Tripepi 1993), the physiological state of the donor plant (Bonga and Von Aderkas 1992), and the combination of plant growth regulators in the medium (Skoog and Miller 1957).…”