Burkholderia phytofirmansPsJN promotes in vitro rooting and acclimatization ofHelleborus

Abstract

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 o 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 o 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 and NAA 1 mg/L 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.

Using plant growth-promoting microorganisms (PGPMs) to improve plant development under in vitro culture conditions

“…At this point, the large number of studies available in the scientific literature provide sufficient evidence to support the use of PGPMs to improve the efficiency of in vitro induction and development of adventitious roots. The use of microorganisms in in vitro culture to promote rooting has resulted in encouraging results in many plant species such as one belonging to Helleborus genus (Orlikowska et al, 2017a), Photinia x fraseri Dress (Larraburu et al 2007) or P. avium (Quambusch et al 2016). The latter studies combined the supplementation of the culture medium with hormones and the inoculation with microorganisms.…”

Application and Improvement of In Vitro Culture Systems for Commercial Production of Ornamental, Fruit, and Industrial Plants in Poland

“…could reduce the stress from overheating. It turned out that the inoculation of the microshoots with this bacterium positively influences the quality of the root system, increasing the number of roots three times and their length twice, thus improving acclimatization (Orlikowska et al, 2015). However, this bacterium showed no effect on raspberry cultures, possibly because of its inability to colonize this particular species.…”