Burkholderia phytofirmans PsJN promotes in vitro rooting and acclimatization of Helleborus
Helleborus is a valuable ornamental plant, flowering in early spring or winter. Its hybrid cultivars can be propagated vegetatively, including in vitro via axillary shoots. One of the obstacles preventing effective micropropagation is the necessity for culture to be kept at a temperature of around 15°C, which additionally increases costs. Knowledge obtained up to date shows that inoculating plants with bacteria Burkholderia phytofirmans PsJN can increase their tolerance to the non-optimal growth temperature. In this study, we tested whether the bacterium, which is known to produce a relatively high amount of IAA and demonstrates ACC deaminase activity, was able to stimulate Helleborus root formation at a temperature of 23°C. In our experiment, the microshoots cultured without auxin and not inoculated with PsJN rooted in 83% with 1.7 roots of 0.6 cm long. The microshoots, which were induced to root with auxins IBA 3 mg L-1 and NAA 1 mg L-1 but not inoculated, were rooted in 94% with 2.0 roots of 1.1 cm long. A similar result was obtained for the microshoots not rooted on auxin containing medium but inoculated with PsJN 95% rooted shoots with 2.3 roots of 1.2 mm long. The microshoots that were induced to root on the auxins containing medium and then inoculated with PsJN were rooted in 100% with 6.9 roots of 2.1 cm long. Almost all microplants from this treatment acclimatized to greenhouse conditions and grew vigorously, then flowered after winter precooling in a mildly heated greenhouse.
Orlikowska, T., Nowak, K. and Ogórek, L. 2017. Burkholderia phytofirmans PsJN promotes in vitro rooting and acclimatization of Helleborus. Acta Hort. (ISHS) 1155:513-518
auxins, beneficial bacteria, cytokinins, non-optimal temperature, ornamental plants