In recent years, naturally occurring tetrahydro-β-carboline (THC) alkaloids and their derivatives have been of biological interest. However, few studies and developments have reported the use of such structures in managing plant bacterial diseases. Herein, an array of novel THC derivatives containing an attractive 1,3-diaminopropan-2-ol pattern were prepared to evaluate the antiphytopathogen activity in vitro and in vivo and explore innovative antibacterial frameworks. Notably, target compounds exhibited excellent activities against three rebellious phytopathogens, namely, Pseudomonas syringae pv. actinidiae (Psa), Xanthomonas axonopodis pv. citri, and Xanthomonas oryzae pv. oryzae, at related optimal EC 50 values of 2.39 (II 9 ), 2.06 (I 23 ), and 1.69 (II 9 ) μg/mL, respectively. These effects were superior to those of the parent structure 1,2,3,4-THC and positive controls. In vivo assays showed that II 9 exhibited excellent control efficiencies of 51.89 and 65.45% at 200 μg/mL against rice bacterial blight and kiwifruit bacterial canker, respectively, and I 23 substantially relieved the citrus canker on the leaves. Antibacterial mechanisms indicated that these THC compounds could induce the increment of reactive oxygen species and subsequently endow the tested bacteria with distinct apoptotic behavior. In addition, II 9 could alleviate the hypersensitive response and pathogenicity of Psa. Overall, these simple THC derivatives can be further developed as versatile antibacterial agents.

Supramolecular chemistry provides huge potentials and opportunities in agricultural pest management. In an attempt to develop highly bioactive, eco-friendly, and biocompatible supramolecular complexes for managing intractable plant bacterial diseases, herein, a type of interesting adamantane-functionalized 1,3,4-oxadiazole was rationally prepared to facilitate the formation of supramolecular complexes via β-cyclodextrin−adamantane host−guest interactions. Initial antibacterial screening revealed that most of these adamantane-decorated 1,3,4-oxadiazoles were obviously bioactive against three typically destructive phytopathogens. The lowest EC 50 values could reach 0.936 (III 18 ), 0.889 (III 18 ), and 2.10 (III 19 ) μg/mL against the corresponding Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas axonopodis pv. citri (Xac), and Pseudomonas syringae pv. actinidiae (Psa). Next, the representative supramolecular binary complex III 18 @β-CD (binding mode 1:1) was successfully fabricated and characterized by 1 H nuclear magnetic resonance (NMR), isothermal titration calorimetry (ITC), high-resolution mass spectrometry (HRMS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Eventually, correlative water solubility and foliar surface wettability were significantly improved after the formation of host−guest assemblies. In vivo antibacterial evaluation found that the achieved supramolecular complex could distinctly alleviate the disease symptoms and promote the control efficiencies against rice bacterial blight (from 34.6−35.7% (III 18 ) to 40.3−43.6% (III 18 @β-CD)) and kiwi canker diseases (from 41.0−42.3% (III 18 ) to 53.9−68.0% (III 18 @β-CD)) at 200 μg/mL (active ingredient). The current study can provide a feasible platform and insight for constructing biocompatible supramolecular assemblies for managing destructive bacterial infections in agriculture.

A safe, biocompatible, and stimuli-responsive cucurbit [7]urilmediated supramolecular bactericidal nanoparticle was fabricated by encapsulating a highly bioactive carbazole-decorated imidazolium salt (A 1 , EC 50 = 0.647 μg/mL against phytopathogen Xanthomonas oryzae pv oryzae) into the host cucurbit[7]uril (CB[7]), thereby leading to self-assembled topographies from microsheets (A 1 ) to nanospheroidal architectures (A 1 @ CB[7]). The assembly behaviors were elucidated by acquired single-crystal structures, 1 H NMR, ITC, and X-ray powder diffraction experiments. Complex A 1 @CB[7] displayed lower phytotoxicity and could efficiently switch on its potent antibacterial ability via introducing a simple competitor 1-adamantanamine hydrochloride (AD). In vivo antibacterial trials against rice bacterial blight revealed that A 1 @CB[7] could relieve the disease symptoms after being triggered by AD and provide a workable control efficiency of 42.6% at 100 μg/mL, which was superior to bismerthiazol (33.4%). These materials can provide a viable platform for fabricating diverse stimuli-responsive supramolecular bactericides for managing bacterial infections with improved safety.

The effective prevention of plant bacterial infections has been complicated and challenged by unceasing bacterial resistance. The application of traditional bactericides has achieved certain effects to alleviate this situation. However, these chemicals also have limitations, such as short half-life in reality, limited bioavailability, and pollutant emission from their formulations. These disadvantages drive the demand for promoting antibacterial therapeutics. Self-assembled nanostructures based on amphiphiles have inherently versatile characteristics, including high durability, good bioavailability, sustained release, and regenerability. As such, they have garnered wide interest because of these advantages that may serve as a feasible platform for the management of pathogenic infections. Flexible tuning of the shapes of these nanostructures by manipulating noncovalent driving forces consequently results in different levels of antibacterial activity. Herein, an antibacterial amphiphile, 1-[11-(9-anthracenylmethoxy)-11-oxoundecyl]pyridinium bromide (AP), was assembled into microfilms in screening medium. Hierarchical nanofibers were constructed by introducing an electron-deficient trinitrofluorenone (TNF) molecule into the assembling system directed by charge-transfer (CT) interactions to further investigate the contribution of aggregate shape to bioactivity. Biological evaluation revealed that antibacterial efficacy improved after CT complex formation. This study provides an innovative platform for developing versatile assembled structures for restraining the propagation of plant pathogens and an improved understanding of the actual interplay between the selfassembly and antibacterial ability of bactericides at the supramolecular level.

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