Approaches on vegetative propagation of difficult-to-root Salix caprea

Abstract

In the framework of a willow rust research project, it was necessary to include vegetatively propagated plant material of selected sallow trees (Salix caprea L.) into biotests for identification of pathotypes. Since it was not possible to root sufficient clonal plants by conventional cutting propagation, the applicability of tissue culture methods was tested. From 10 selected donor trees of Salix caprea newly sprouted shoots were harvested and transferred to nutrient media after surface disinfection. The cultures were grown at 20--22 °C, illuminated with warm-white fluorescent tubes. The majority of shoot tips and nodal segments died during the first month, but only with nursery-grown plants this was caused by bacteria contamination. Two clones could be established easily on hormone-free medium. Five clones could be initiated only after repeated subcultures on various media variants. Three clones failed completely. Different basic media compositions were tested and Woody Plant Medium, supplemented with 0.1% activated charcoal, proved to be best for most of the sallow clones. Well developed rooted plantlets were used in vitro for microcutting propagation. The resulting plants were transferred to soil and could be included in the rust screening program after acclimatising. The applicability of micropropagation for selected Salix caprea donor trees was strongly depending on the genotype. But the comparison of results from microcuttings with conventional cutting propagation showed that these methods were successful for different clones each.