Plant growth-promoting abilities and community structure of culturable endophytic bacteria from the fruit of an invasive plant Xanthium italicum

Potential of utilizing pathogen-derived mycotoxins as alternatives to synthetic herbicides in controlling the noxious invasive plant Xanthium italicum

Discovery of environmentally friendly agents for controlling alien invasive species (AIS) is challenging and in urgent need as their expansion continues to increase. Xanthium italicum is a notorious invasive weed that has caused serious ecological and economic impacts worldwide. For the purpose of exploring the possibility of utilizing herbicidal mycotoxins to control this species, three compounds, a new compound, curvularioxide (1), a new naturally occurring compound, dehydroradicinin (2), and a known compound, radicinin (3), were isolated via activity-guided fractionation from the secondary metabolites of the pathogenic Curvularia inaequalis, which was found to infect X. italicum in natural habitats. All isolated compounds exhibited potent herbicidal activity on receiver species. It is noteworthy to mention that their effects on X. italicum in our bioassays were equivalent to the commercial herbicide glyphosate. Subsequent morphological analysis revealed that application of radicinin (3) severely hindered X. italicum seedlings' hypocotyl and root development. Malondialdehyde content and the activity of catalase and peroxidase of the seedlings were also significantly different from the control, implying the occurrence of induced oxidative stress. Our results suggest that pathogens infecting invasive plants might be valuable resources for developing safer herbicides for controlling weeds. © 2023 Society of Chemical Industry.

Improved growth and metabolite accumulation in Codonopsis pilosula (Franch.) Nannf. by inoculation with the endophytic Geobacillu sp. RHBA19 and Pseudomonas fluorescens RHBA17

In this study, we focused on the plant-growth-promoting properties of two strains isolated from Codonopsis pilosula, and the effect of inoculation with different strain treatments on physiological and metabolite accumulation of C. pilosula. The strains RHBA19 and RHBA17 were isolated and identified as Geobacillu sp. and Pseudomonas fluorescens, respectively. The two strains produced indole acetic acid (IAA), siderophore, biofilm, and various exoenzymes. Based on the pot experiments, inoculation of RHBA19 (G group) and the two mixed bacteria (M group) significantly improved the growth, root development, and photosynthesis of C. pilosula. Compared with the no-inoculation group (CK), the total polysaccharide content of root in the G and M groups was dramatically enhanced by 59.27% and 96.07%, and the lobetyolin (root) improved by 58.4% and 66.0%, respectively. After inoculation with bacteria agents, the activities of antioxidant enzymes (CAT, POD, SOD) of C. pilosula increased differentially. Inoculation with two types of bacterial agents significantly increased the activities of sucrose synthase (SS) and sucrose phosphate synthase (SPS) in root, and phenylalanine ammonia lyase (PAL) in leaf of C. pilosula. In addition, the content of signaling molecules (NO and H₂O₂) in three types of tissue increased significantly. The magnitude of these results was higher with mixtures than with individual strains. These results imply that the two types of bacterial agents induce physiological metabolism changes to accumulate polysaccharides and lobetyolin by regulating stress resistance enzymes and signal molecules, especially NO and H₂O₂.