The Efficacy and Underlying Mechanism of Sulfone Derivatives Containing 1,3,4-oxadiazole on Citrus Canker.

Pei Li,Yuhua Ma,Jiawen Yan,Hui Luo,Zhuang Wang,Junliang Zhou,Yongya Mao

doi:10.3390/molecules200814103

Pei Li, Yuhua Ma + Show 5 more

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https://doi.org/10.3390/molecules200814103

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Abstract

The objectives of the current study were to isolate and identify the pathogen responsible for citrus canker and investigate the efficacy of sulfone derivatives containing 1,3,4-oxadiazole moiety on controlling citrus canker caused by Xanthomonas citri subsp. citri (Xcc) under in vitro and field conditions. In an in vitro study, we tested eight sulfone derivatives against Xcc and the results demonstrated that compound 3 exhibited the best antibacterial activity against Xcc, with a half-maximal effective concentration (EC50) value of 1.23 μg/mL, which was even better than those of commercial bactericides Kocide 3000 (58.21 μg/mL) and Thiodiazole copper (77.04 μg/mL), respectively. Meanwhile, under field experiments, compound 3 treatments demonstrated the highest ability to reduce the disease of citrus canker in leaves and fruits in two different places relative to an untreated control as well as the commercial bactericides Kocide 3000 and Thiodiazole copper. Meanwhile, compound 3 could stimulate the increase in peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia lyase (PAL) activities in the navel orange leaves, causing marked enhancement of plant resistance against citrus canker. Moreover, compound 3 could damage the cell membranes, destruct the biofilm formation, inhibit the production of extracellular polysaccharide (EPS), and affect the cell membrane permeability to restrain the growth of the bacteria.

Highlights

Citrus canker, a serious disease of most commercial citrus cultivars in subtropical citrus-producing areas of the world, has a significant impact on national and international citrus markets and trade [1,2,3].Citrus canker is a disease that is characterized by the formation of necrotic raised lesions on leaves, stems, and fruit of citrus trees, including limes, oranges, and grapefruit
The enzyme activities changes of POD, polyphenol oxidase (PPO), and phenylalanine ammonia lyase (PAL) preliminarily demonstrated that compound 3 can improve the disease resistance of plants that rely on inducible defense responses in the form of enzymes that are activated for controlling citrus canker
The pathogenic bacterium Xanthomonas citri subsp. citri (Xcc), the cause of citrus canker, was isolated from an infected corm of navel orange fruit and the species was identified via PCR analysis and the amplicons were sequenced

Summary

Introduction

Citrus canker is a disease that is characterized by the formation of necrotic raised lesions on leaves, stems, and fruit of citrus trees, including limes, oranges, and grapefruit. Once infected with the disease, citrus canker can cause defoliation, twig dieback, general tree decline, blemished fruit, and premature fruit drop [4]. Citri (Xcc) [5,6,7]. Citrus canker is caused by the bacterial pathogen Xanthomonas citri subsp. This bacterium is dispersed in rain splash often associated with wind [8,9,10,11,12] and enters the plant directly through stomata or through wounds, and it grows in the intercellular spaces of the spongy mesophyll [1]. Copper-containing bactericides are the primary control measure for citrus canker

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