Isolation, structural elucidation and bioherbicidal activity of an eco-friendly bioactive 2-(hydroxymethyl) phenol, from Pseudomonas aeruginosa (C1501) and its ecotoxicological evaluation on soil.
Agricultural production in many emerging economies suffer losses owing to the challenges posed by weeds. Owing to cost, ecological, environmental and other human health safety issues regarding the use and application of chemicals as a control option against invasive weeds, there has been a renewed focus to explore alternative and safer methods such as biotechnology. In this study, we explored the use of some beneficial rhizobacteria as a possible alternative to chemicals. The impact of the newly characterized strains of rhizobacteria (acting as a bioherbicide), was investigated to ascertain whether they had any impact on the soil health - and here its effect on the soil organic carbon content, soil respiration, and enzymatic activities were investigated. Several bioactive metabolites extracted from the rhizobacteria were further screened (via leaf necrosis assays, under laboratory and screen house), for their selective efficacy against a range of test plants, of which the C1501 strain showed the most promising results for good herbicidal activity. In this study, the active compound is identified by combined spectroscopic methods (1D and 2D NMR techniques) as a 2-(hydroxymethyl) phenol. The C1501 strain were also shown to significantly decrease the dry-weight of A. hybridus seedlings. However, there was no noticeable or adverse effect observed in sorghum seedlings. A low adverse effect on soil was also shown after day 70 of the experiment, where the 2-(hydroxymethyl) phenol treated soil had the highest release of CO2 (867.50 mg CO2 kg-1 soil hr-1) when compared to the glyphosate treated soil (96.73 mg CO2 kg-1 soil hr-1). Similarly, the enzymatic activities and the soil carbon content were significantly higher in the 2-(hydroxymethyl) phenol treated soil when compared to the control. The C1501 strain was found to have an eco-friendly profile; was cheap and could be used as a good alternative product to chemical herbicides. This strain could thus serve as a good candidate bioherbicide for the control of the A. hybridus weed and possibly be considered for use in a large scale production system, which would be beneficial for a sustainable organic agricultural setting that improves yield and enhances food security.