Impact of Burkholderia phytofirmans strain PsJN on the ex vitro acclimatization and in vitro propagation of tissue cultured Dionaea muscipula (Venus fly trap)

Dionaea muscipula, Venus fly trap, is an endangered plant that is propagated primarily through tissue culture. Tissue cultured plants must be acclimatized to their new environments when removed from their test tubes and the ensuing stress can result in plant mortality. A plant growth promoting rhizobacterium, Burkholderia phytofirmans strain PsJN, has been utilized in biotic hardening of tissue cultured plants and in the amelioration of stresses, particularly drought stress in potted plants. We investigated whether this bacterium could improve either propagation or acclimatization of tissue cultured Venus fly traps. Standardized inoculations were performed by adjusting cell density of inoculant by spectrophotometry. In ex vitro acclimatization, inoculation with the bacteria significantly improved survival but only in nonsterile soil media. Initial in vitro inoculations produced negative interactions with significant reduction in propagules and biomass in the plant and bacterial growth on the media. A modified plant tissue culture media using maltose instead of sucrose as a sugar source was created to address this problem. Inoculated plants grown in the maltose media were not significantly different than the mock inoculated controls in terms of biomass, traps produced and propagules produced. Additionally the bacteria did not visibly grow on media supplemented with maltose rather than sucrose as a sugar source. Plant infection was confirmed through fluorescence microscopy. Colony density estimates for both rhizosphere and endosphere populations of the bacteria in tissue cultured plants were generated using plate counting. These findings indicate that Burkholderia phytofirmans strain PsJN may be useful in reduction of mortality during acclimatization of Dionaea muscipula, but only in nonsterile growth situations or when drought stress is expected. The use of alternative tissue culture media using maltose when propagating biotized fly traps in vitro is an improvement over sucrose containing media. Further work must be done to determine whether mortality reduction by strain PsJN is the result of stress reduction by the endophyte or competitive inhibition of an unknown microbial agonist