Persistence ofPseudomonas fluorescensLBUM677 in the rhizosphere of corn gromwell (Buglossoides arvensis) under field conditions and its impact on seed oil and stearidonic acid bioaccumulation

Abstract

Aims The aim of this study was to evaluate the persistence of Pseudomonas fluorescens LBUM677 in the rhizosphere of Buglossoides arvensis under agricultural field conditions and determine if B. arvensis intraspecific genetic variations affect the capacity of LBUM677 to colonize its rhizosphere and increase seed oil and stearidonic acid (SDA) accumulation. Methods and Results Two field experiments were performed to: (i) study the persistence of various concentrations of LBUM677 inoculated in the rhizosphere of B. arvensis and determine a minimum inoculation threshold required to maximize biological activity; and (ii) study the impact of B. arvensis intraspecific genetic variations on LBUM677 rhizosphere colonization and seed oil and SDA accumulation. In order to track LBUM677 populations in soil over time, a specific quantitative polymerase chain reaction assay was developed. Inoculation with a minimum of 109 LBUM677 bacterial cells per plant was determined as a threshold to promote maximum B. arvensis rhizosphere colonization and seed oil and SDA accumulation. Buglossoides arvensis intraspecific genetic variations had an impact on rhizosphere colonization, B. arvensis seed oil and SDA accumulation, where two cultivars benefited more than others from LBUM677 inoculation. Conclusions LBUM677 can colonize the rhizosphere and increase seed oil and SDA yields in B. arvensis plants in a cultivar‐dependant manner. Significance and Impact of the Study LBUM677 shows potential to be used as a biofertilizer to specifically increase seed oil and SDA yields in B. arvensis. This will in turn promote the development of an economically viable agricultural‐based approach as an alternative for producing high‐quality polyunsaturated fatty acids.

Pseudomonas fluorescens LBUM677 differentially increases plant biomass, total oil content and lipid composition in three oilseed crops

“…LBUM677 was able to establish itself in the rhizosphere of the three plant species under study at similar levels, indicating that none of the plants had a significant effect on LBUM677's colonization abilities. The levels observed for the three plant species were higher than those previously measured in B. arvensis plants; however, this could be due to the previous levels having been measured in field settings and not in a controlled environment, as in this study (Novinscak and Filion , ). The results obtained in this study on the influence of different plant species on the rhizocompetence of Pseudomonas spp.…”

“…also have, but to a lesser extent, been studied for their ability to increase seed oil content as well as fatty acid composition of oilseed crops (Kumar et al ). Previous studies by our research group have shown that P. fluorescens LBUM677 was able to increase oil and SDA yield in B. arvensis plants grown under field conditions (Novinscak and Filion , ). In this study, P. fluorescens LBUM677 colonization resulted in a significant increase in oil yield for all three plant species under study but led to a general plant growth promotion in only two out of three species, B. napus and B. arvensis .…”

“…However, the effects of this bacterium on B. napus and G. max should be examined under field conditions to ascertain that the bacterium displays its oil‐increasing effects in the field as environmental conditions between controlled and field set‐ups can vary greatly. The ability of LBUM677 to increase the oil yield and SDA content of B. arvensis in the field has been previously demonstrated (Novinscak and Filion , ). Finally, it may be worth in future experiments to test if the cell‐free conditioned medium in which LBUM677 was grown can also influence the physiology of the plant as the experimental procedure used in this work cannot rule out this possibility.…”

“…The DNA quantity and quality was evaluated using a NanoDrop ND‐1000 spectrophotometer (NanoDrop Technologies, Wilmington, DE). A previously developed PCR primer pair and a TaqMan probe targeting a specific molecular marker (61 bp) in P. fluorescens LBUM677 was used to specifically detect and quantify rhizosphere soil populations of LBUM677 (Novinscak and Filion ). qPCR reactions were performed in triplicate on a CFX Connect Real‐Time PCR Thermocycler (BioRad, Mississauga, ON, Canada) using the iTaq Universal Probe Supermix kit and protocol (BioRad).…”

“…Recently, Buglossoides arvensis has gained nutraceutical interest due to its accumulation of the omega‐3 fatty acid stearidonic acid (SDA) in its seeds, representing approximately 20% of its oil content (Cumberford and Hebard ; Lefort et al ). Our research group has previously determined that Pseudomonas fluorescens LBUM677 was capable of significantly increasing SDA accumulation in B. arvensis (Novinscak and Filion , ). However, the impact of LBUM677 on other oilseed crops, such as B. napus and G. max , has never been characterized.…”