Visible-Light-Driven Zinc Oxide Quantum Dots for the Management of Bacterial Fruit Blotch Disease and the Improvement of Melon Seedlings Growth

Abstract

Bacterial fruit blotch is one of the most destructing diseases of melon producing-regions. Here, zinc oxide quantum dots (ZnO QDs) were synthesized, and their antibacterial activity against Acidovorax citrulli was investigated. The results indicated that the obtained ZnO QDs displayed 5.7-fold higher antibacterial activity than a commercial Zn-based bactericide (zinc thiazole). Interestingly, the antibacterial activity of ZnO QDs irradiated with light was 1.8 times higher than that of the dark-treated group. It was because ZnO QDs could induce the generation of hydroxyl radicals and then up-regulate the expression of oxidative stressrelated genes, finally leading to the loss of cell membrane integrity. A pot experiment demonstrated that foliar application of ZnO QDs significantly reduced the bacterial fruit blotch disease incidence (32.0%). Furthermore, the supply of ZnO QDs could improve the growth of infected melon seedlings by activating the antioxidant defense system. This work provides a promising light-activated quantum-bactericide for the management of pathogenic bacterial infections in melon crop protection.

Visible‐light‐driven water‐soluble zinc oxide quantum dots for efficient control of citrus canker

“…2(b)). Our results are consistent with the light‐enhanced antimicrobial activity of ZnO QDs shown previously 31,35 . Our study shows stronger a antibacterial activity of ZnO QDs compared with that of other chemical pesticides (Supporting Information, Table S1), 4 indicating good application potential for the use of ZnO QDs as a control agent for citrus canker.…”

“…3(g), the rod‐like structure of the bacteria remained unchanged before and after light treatment with ZnO QDs, and the cell membrane did not show any significant rupture. This finding is inconsistent with the results of Wang et al 31 . but consistent with the results of Du et al ., 35 suggesting that water‐soluble ZnO QDs do not cause cell membrane fragmentation with a short exposure time and that other factors have important roles in the photocatalytic antibacterial activity of ZnO QDs.…”

“…The amounts of Zn ions released from ZnO QDs in different solutions were analysed using an inductively coupled plasma optical emission spectrometer (ThermoFisher, USA; further details are provided in Supporting Information, Text S3). 31 …”

“…The observed production of •OH, •O − 2 and 1 O 2 agrees with the results of Chen et al 14 and Zhou et al, 34 but includes more ROS species than observed in the previous study of ZnO QDs against Acidovorax citrulli (•OH). 31 It has been reported that the photo-induction of water-soluble ZnO QDs can generate various types of ROS (•OH, •O − 2 and 1 O 2 ) because of its high specific surface area and large number of oxygen vacancy defects. 34 Given this, the water-soluble ZnO QDs may have greater oxygen vacancy defects and ROS generation factors than conventional ZnO QDs.…”

“…[24][25][26] In comparison with conventional-scale ZnO nanoparticles, ZnO quantum dots (ZnO QDs) show higher plant transport efficiency, 27,28 higher photocatalytic efficiency and higher antibacterial activity. 29,30 ZnO QDs can effectively control plant bacterial diseases, such as bacterial fruit blotch disease, 31 citrus canker disease and citrus huanglongbing disease, 28 mainly by the generation of ROS and the release of Zn 2+ during the binding of ZnO QDs and bacteria. Studies have shown that the antibacterial activity of nanomaterials is closely related to their water dispersibility, with better dispersion being correlated with more significant antibacterial activity.…”