Scientia Agricultura Sinica ›› 2026, Vol. 59 ›› Issue (12): 2623-2636.doi: 10.3864/j.issn.0578-1752.2026.12.007

• PLANT PROTECTION • Previous Articles     Next Articles

Inhibitory Effects and Mechanisms of Juglone Against Walnut Blight Pathogens

SU Yi(), SUN LeYuan, WU ChengXu, JI XinYing, NIE RuiNing, XIA Juan, HAN ZhuoRan, ZHOU Ye(), ZHANG JunPei()   

  1. Research Institute of Forestry, Chinese Academy of Forestry/State Key Laboratory of Tree Genetics and Breeding/Key Laboratory of Forest Cultivation and Management of National Forestry and Grassland Administration, Beijing 100091
  • Received:2026-01-31 Accepted:2026-04-05 Online:2026-06-16 Published:2026-06-16
  • Contact: ZHOU Ye, ZHANG JunPei

Abstract:

【Objective】This study aimed to determine the antibacterial activity of juglone against the major pathogens causing walnut blight, Xanthomonas arboricola pv. juglandis (Xaj) and Pantoea agglomerans (Pa), and to investigate its mechanism of action, so as to provide a theoretical basis for the green control of walnut blight.【Method】The antibacterial activity of juglone against Xaj and Pa was evaluated in vitro by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Growth curves and resazurin staining were used to characterize the dynamic changes in the viability of Xaj and Pa after juglone treatment. Scanning electron microscopy (SEM) was used to observe alterations in the cell surface and morphology of the two pathogens. Relative electrical conductivity and cell surface hydrophobicity were measured to reveal the effects of juglone on membrane integrity and surface properties. Changes in pathogen protein and nucleic acid electrophoretic profiles were analyzed to assess the interference of juglone with nucleic acids, proteins, and related biological processes. UV absorption spectroscopy and molecular docking were applied to clarify the interaction mode between juglone and pathogen DNA. Leaf inoculation assay was conducted to evaluate the protective effect of juglone against walnut blight on leaves.【Result】Juglone showed obvious antibacterial activity against the major pathogens causing walnut blight, and Xaj was more sensitive than Pa. The MIC values of juglone against Xaj and Pa were 0.1 and 0.4 mg·mL-1, respectively, while the corresponding MBC values were 0.2 and 0.8 mg·mL-1. Growth curve analysis showed that juglone inhibited the growth of both pathogens in a concentration-dependent manner. After treatment with 0.5×MIC juglone for 30 min, the cell viability of Xaj and Pa decreased by 35.25% and 37.43%, respectively. SEM observations showed that juglone treatment caused obvious morphological abnormalities in bacterial cells, including shrinkage, depression, and even rupture. After treatment with 0.5×MIC juglone, the relative electrical conductivity and cell surface hydrophobicity of both pathogens increased, accompanied by increased leakage of intracellular nucleic acids, proteins, and other substances, indicating that juglone disrupted cell membrane integrity. Ultraviolet absorption spectroscopy and molecular docking suggested that juglone might interact with bacterial DNA through groove binding mediated by non-covalent interactions such as hydrogen bonding. The detached-leaf assay showed that application of 1×MIC juglone significantly reduced the lesion area on infected walnut leaves, exhibiting good leaf control efficacy.【Conclusion】Juglone showed obvious antibacterial activity against the pathogens causing walnut blight. Its antibacterial effect was mainly achieved by disrupting cell membrane integrity, increasing membrane permeability, and further affecting nucleic acid- and protein-related biological processes. In addition, juglone showed control potential against walnut blight on leaves.

Key words: walnut blight, juglone, antibacterial mechanism, Xanthomonas arboricola pv. juglandis, Pantoea agglomerans

Fig. 1

Growth curves of walnut blight pathogens under juglone treatments"

Fig. 2

Effects of juglone treatments on the cell viability of walnut blight pathogens"

Fig. 3

Effects of juglone treatments on the morphology of walnut blight pathogens"

Fig. 4

Effects of juglone treatments on the relative electrical conductivity of walnut blight pathogens"

Fig. 5

Effects of juglone treatments on the cell surface hydrophobicity of walnut blight pathogens"

Fig. 6

Effects of juglone treatments on intracellular substance leakage in walnut blight pathogens"

Fig. 7

SDS-PAGE analysis of proteins from walnut blight pathogens following juglone treatments"

Fig. 8

Electrophoretic profiles of nucleic acids from walnut blight pathogens under juglone treatments"

Fig. 9

UV absorption spectra of the interaction between juglone and pathogen DNA"

Fig. 10

Interaction model of the juglone-DNA complex a: 1BNA; b: 1CGC; c: 1ZEW; d: 4C64"

Table 1

Molecular docking results"

对接体系
Docking system
结合能Binding energy (kJ·mol-1) 氢键作用(核苷酸-氢键长度)
Hydrogen bonding (nucleotide-hydrogen bond length, Å)
疏水作用(5 Å范围内核苷酸)
Hydrophobic interaction (nucleotides<5 Å)
1BNA (Fig. 10-a) -27.21 DG10 (A) (2.8, 3.0, 3.1); DG16 (B) (2.9, 3.1) DC11 (A); DA17 (B); DA18 (B)
1CGC (Fig. 10-b) -26.80 DG3 (A) (2.9, 3.2); DC18 (B) (2.8); DG19 (B) (3.0, 3.1) DG4 (A); DG5 (A)
1ZEW (Fig. 10-c) -27.21 DT3 (A) (3.2); DC4 (A) (2.8, 2.9); DG17 (B) (2.8) DA18 (B); DG19 (B); DG20 (B)
4C64 (Fig. 10-d) -27.63 DG10 (A) (2.8, 3.0); DC15 (B) (2.7); DG16 (B) (3.0) DC11 (A); DG12(A); DA17 (B)

Fig. 11

Control efficacy of juglone against walnut blight on detached leaves"

Table 2

Lesion area on inoculated leaves (cm2)"

病原菌Pathogen 仅接病菌Pathogen inoculation only 1×MIC胡桃醌处理Juglone treatment 对照Control
核桃黄单胞杆菌Xaj 0.030±0.007a 0.005±0.002b 0.001±0.0001c
成团泛菌Pa 0.027±0.013a 0.004±0.003b 0.001±0.0002c

Fig. 12

Proposed antibacterial mechanism of juglone against walnut blight pathogens"

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