Long-term effects of culture establishment from shoot-tip explants in micropropagating oak (Quercus robur L)

Abstract

Summary — This paper describes a method of in vitro culture establishment from shoot-tip explants taken from juvenile and mature plant material for oak (table I). The cultures established from shoot-tips were then compared with cultures derived from nodal explants for decontamination, their initial reactivity and their potential for long-term propagation. For the decontamination, the results showed that the use of shoot-tip explants is useful only when culture establishement must be made directly from source-plants growing in situ (table II). Otherwise, the use of nodal explants taken from source-plants that are maintained under active growth and controlled sanitary conditions is more advisable due to a better initial reactivity. As regards the potential for long-term propagation, the culture establishment from shoot-tips appeared truly interesting only in the case of recalcitrant clones and/or insufficient optimization of the culture methods (fig 1). However, this positive effect attenuated after a 6-7 month culture period, and the clonal effects and the management of the media became the determining factors of the culture behaviour whatever the initial explant used (fig 2).

Why and How Using Micropropagated Trees rather than Germinations for Controlled Synthesis of Ectomycorrhizal Associations?

“…Morphogenetic gradients along the stem and various growth responses of the explants are observed in relation to the initial position of the lateral buds from which they are obtained. Juncker and Favre (1994) noticed this influence and used only basal nodes for micropropagation as these produced longer shoots with more numerous leaves. San-Jose et al (1988) observed that the percentage of explants forming shoots in all clones was greater for apical than for nodal culture and the number of shoots per explant was greater for nodal than for apical culture.…”

“…In other cases, a progressive degeneration can occur at a time at which long-term culture is occurring. After 6-7 months, the clonal effect is the most important determining factor of the behavior of a long-term culture (Juncker and Favre 1994).…”

“…An optimal total N concentration was essential to avoid degeneration of the oak clone (Juncker and Favre 1994). For this reason, we used two basic media: the MS half-strength culture medium with 1/8 or 1/4 NH 4 NO 3 and the modified GD Medium as proposed by Favre (1994) (Gresshoff andDoy 1972;Murashige and Skoog 1962;and Table 1).…”

Technological advances in temperate hardwood tree improvement including breeding and molecular marker applications

“…Mature clones (grafted plants) of P. serotina (black cherry) have been micropropagated and field tested (Tricoli et al 1985;Maynard 1994). Several Quercus species (Q. petraea, Q. robur, Q. rubra, and Q. suber) have been micropropagated from mature explants (San-Jose et al 1990;Romano et al 1992;Juncker and Favre 1994;Sanchez et al 1996;Chalupa 2000;Vidal et al 2003). Black locust (R. pseudoacacia) can be propagated using dormant vegetative buds, shoot tips, and nodal segment explants of mature trees (Davis and Keathley 1987a, b;Kamlesh et al 1995;Han et al 1997;Nakatsubo et al 2003).…”

Quercus spp. (Oak): In Vitro Culture and Production of Tannins

“…Culture establishment from explants with high organogenetic potential such as shoot tips, induced a temporary Stimulation of shoot growth and multiplicalion factor which disappeared after four to six subcultures (Juncker and Favre 1993).…”