Abstract
Schisandra chinensis extracts (SEs) have traditionally been used as an oriental medicine for the treatment of various human diseases, however, their further application in the biocontrol of plant disease remains poorly understood. This study was conducted to develop eco-friendly botanical pesticides from extracts of S. chinensis and assess whether they could play a key role in plant disease defense. Concentrated active fractions (SE-I, SE-II, and SE-III) were obtained from S. chinensis via specific extraction and separation. Then, lignan-like substances, such as Schisanhenol B, were detected via High-Performance Liquid Chromatography-ElectroSpray Ionization-Mass Spectrometry (HPLC-ESI-MS) analyses of the active fractions. Moreover, the results from biological tests on colony growth inhibition and spore germination indicated that SE-I, SE-II, and SE-III could inhibit hyphal growth and spore generation of three important plant pathogenic fungi (Monilinia fructicola, Fusarium oxysporum, and Botryosphaeria dothidea). The study of the mechanisms of resistant fungi revealed that the oxidation resistance system, including reactive oxygen species (ROS), malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD), was activated. The expression of genes related to defense, such as pathogenesis-related protein (PR4), α-farnesene synthase (AFS), polyphenol oxidase (PPO), and phenylalanine ammonia lyase (PAL) were shown to be up-regulated after treatment with SEs, which suggested an increase in apple immunity and that fruits were induced to effectively defend against the infection of pathogenic fungi (B. dothidea). This study revealed that SEs and their lignans represent promising resources for the development of safe, effective, and multi-targeted agents against pathogenic fungi.
Highlights
Bioactive substances derived from plants play important roles in environmental improvement, food production, food security, and biodiversity conservation
In the study, according to gradient elution, seven fractions were obtained from crude S. chinensis extract and were named S. chinensis fruit extract (SE)-I, SE-II, SE-III, SE-IV, SE-V, SE-VI, and SE-VII (SE series, SEs) according to polarity sequence
The results indicated that SE-I to SE-III had inhibitive effects against M. fructicola, F. oxysporum, and B. dothidea, but their activities varied among the different pathogenic fungi, with the inhibitive ability of SE-III being best of the three candidate fractions based on their EC50 values
Summary
Bioactive substances derived from plants play important roles in environmental improvement, food production, food security, and biodiversity conservation. Research regarding the application of botanical pesticides has shown that such substances are advantageous because of their high selectivity, low toxicity to humans, and biodegradability. Today they are one of the most important potential sources for the creation of new pesticides [6,7,8,9]. Several studies have shown that plant extracts contain active antibacterial ingredients, many of which have been extracted, developed, and applied as botanical fungicides [10,11,12,13]. Identifying which species in the voluminous plant kingdom contain effective concentrations of active substances, and which of the ingredients in the 400,000 known secondary metabolites derived from plants have insecticidal activity [14], has been and will continue to be a puzzle to be solved
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