Enhancement and improvement of selenium in soil to the resistance of rape stem against Sclerotinia sclerotiorum and the inhibition of dissolved organic matter derived from rape straw on mycelium

Synthesis and Antifungal Activity of Norbornene Carboxamide/sulfonamide Derivatives as Potential Fungicides Targeting Laccase

To explore more potential fungicides with new scaffolds, thirty-seven norbornene carboxamide/sulfonamide derivatives were designed, synthesized, and assayed for inhibitory activity against six plant pathogenic fungi and oomycetes. The preliminary antifungal assay suggested that the title derivatives showed moderate to good antifungal activity against six plant pathogens. Especially, compound 6 e presented excellent in vitro antifungal activity against Sclerotinia sclerotiorum (EC50=0.71 mg/L), which was substantially stronger than pydiflumetofen. In vivo antifungal assay indicated 6 e displayed prominent protective and curative effects on rape leaves infected by S. sclerotiorum. The preliminary mechanism research displayed that 6 e could damage the surface morphology and inhibit the sclerotia formation of S. sclerotiorum. In addition, the in vitro enzyme inhibition bioassay indicated that 6 e displayed pronounced laccase inhibition activity (IC50=0.63 μM), much stronger than positive control cysteine. Molecular docking elucidated the binding modes between 6 e and laccase. The bioassay results and mechanism investigation demonstrated that this class of norbornene carboxamide/sulfonamide derivatives could be promising laccase inhibitors for novel fungicide development.

Design, Synthesis, Antibacterial, and Antifungal Evaluation of Phenylthiazole Derivatives Containing a 1,3,4-Thiadiazole Thione Moiety

To effectively control the infection of plant pathogens, we designed and synthesized a series of phenylthiazole derivatives containing a 1,3,4-thiadiazole thione moiety and screened for their antibacterial potencies against Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, as well as their antifungal potencies against Sclerotinia sclerotiorum, Rhizoctonia solani, Magnaporthe oryzae and Colletotrichum gloeosporioides. The chemical structures of the target compounds were characterized by 1H NMR, 13C NMR and HRMS. The bioassay results revealed that all the tested compounds exhibited moderate-to-excellent antibacterial and antifungal activities against six plant pathogens. Especially, compound 5k possessed the most remarkable antibacterial activity against R. solanacearum (EC50 = 2.23 μg/mL), which was significantly superior to that of compound E1 (EC50 = 69.87 μg/mL) and the commercial agent Thiodiazole copper (EC50 = 52.01 μg/mL). Meanwhile, compound 5b displayed the most excellent antifungal activity against S. sclerotiorum (EC50 = 0.51 μg/mL), which was equivalent to that of the commercial fungicide Carbendazim (EC50 = 0.57 μg/mL). The preliminary structure-activity relationship (SAR) results suggested that introducing an electron-withdrawing group at the meta-position and ortho-position of the benzene ring could endow the final structure with remarkable antibacterial and antifungal activity, respectively. The current results indicated that these compounds were capable of serving as promising lead compounds.

Maleic acid and malonic acid reduced the pathogenicity of Sclerotinia sclerotiorum by inhibiting mycelial growth, sclerotia formation and virulence factors

Sclerotinia sclerotiorum is a necrotrophic plant pathogenic fungus with broad distribution and host range. Bioactive compounds derived from plant extracts have been proven to be effective in controlling S. sclerotiorum. In this study, the mycelial growth of S. sclerotiorum was effectively inhibited by maleic acid, malonic acid, and their combination at a concentration of 2 mg/mL, with respective inhibition rates of 32.5%, 9.98%, and 67.6%. The treatment of detached leaves with the two acids resulted in a decrease in lesion diameters. Interestingly, maleic acid and malonic acid decreased the number of sclerotia while simultaneously increasing their weight. The two acids also disrupted the cell structure of sclerotia, leading to sheet-like electron-thin regions. On a molecular level, maleic acid reduced oxalic acid secretion, upregulated the expression of Ss-Odc2 and downregulated CWDE10, Ss-Bi1 and Ss-Ggt1. Differently, malonic acid downregulated CWDE2 and Ss-Odc1. These findings verified that maleic acid and malonic acid could effectively inhibit S. sclerotiorum, providing promising evidence for the development of an environmentally friendly biocontrol agent.

Nano-selenium enhances melon resistance to Podosphaera xanthii by enhancing the antioxidant capacity and promoting alterations in the polyamine, phenylpropanoid and hormone signaling pathways

Powdery mildew is one of the main problematic diseases in melon production, requiring the use of chemical pesticides with disease-resistant cultivars for control. However, the often rapid acquisition of fungicidal resistance by mildew pathogens makes this practice unsustainable. The identification of crop treatments that can enhance resistance to powdery mildew resistance is therefore important to reduce melon crop attrition. This study indicates that the application of Nano-Se can reduce the powdery mildew disease index by 21-45%. The Nano-Se treatment reduced reactive oxygen species (ROS) and malondialdehyde (MDA) accumulation, with increases in glutathione (GSH), proline and 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH). Increases were also observed in the activities and transcriptional levels of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD). Assays with four different cultivars of melon with differing levels of mildew resistance demonstrated that relative to the control, the Nano-Se treatment resulted in larger responses to mildew infection, including increases in the levels of putrescine (PUT; 43-112%) and spermine (SPM; 36-118%), indoleacetic acid (IAA; 43-172%) and salicylic acid (SA; 24-73%), the activities of phenylalanine ammonium lyase (PAL), trans-cinnamate 4-hydroxylase (C4H) and 4-coumarate: Co A ligase (4CL) of the phenylpropanoid pathway (22-38%, 24-126% and 19-64%, respectively). Key genes in the polyamine and phenylpropanoid pathway were also upregulated. These results indicate that the foliar application of Nano-Se improved melon defenses against powdery mildew infection, with a significant reduction in mildew disease development.

Review on Pesticide Abiotic Stress over Crop Health and Intervention by Various Biostimulants

Plants are essential for life on earth, and agricultural crops are a primary food source for humans. For the One Health future, crop health is crucial for safe, high-quality agricultural products and the development of future green commodities. However, the overuse of pesticides in modern agriculture raises concerns about their adverse effects on crop resistance and product quality. Recently, biostimulants, including microecological bacteria agents and nanoparticles, have garnered worldwide interest for their ability to sustain plant health and enhance crop resistance. This review analyzed the effects and mechanisms of pesticide stress on crop health. It also investigated the regulation of biostimulants on crop health and the multiomics mechanism, combining research on nanoselenium activating various crop health aspects conducted by the authors' research group. The paper helps readers understand the impact of pesticides on crop health and the positive influence of various biostimulants, especially nanomaterials and small molecules, on crop health.

Green Nanopesticide: pH-Responsive Eco-Friendly Pillar[5]arene-Modified Selenium Nanoparticles for Smart Delivery of Carbendazim to Suppress Sclerotinia Diseases

Controlled-release delivery systems have been widely used to improve the efficacy and bioavailability of pesticides and minimize environmental risks. Herein, a fungicide carbendazim (CBZ)-loaded, a kind of nanovalve including trimethylammoniumpillar[5]arene (AP5), and methyl orange (MO)-functionalized mesoporous selenium (MSe) nanopesticides (CBZ@AP5/MSe⊃MO) were prepared. The nanovalve endowed CBZ@AP5/MSe⊃MO with a pH-responsive property, so the CBZ@AP5/MSe⊃MO can respond to the microenvironment of the pathogen Sclerotinia sclerotiorum (S. sclerotiorum). First, MO was shed due to protonation, and AP5-functionalized MSe gradually dissolved in an acid environment. Finally, CBZ was released rapidly. It is reported that AP5 and MO as the host and guest functionalized mesoporous selenium (MSe) have never been applied to agriculture. In vitro release experiments showed that the cumulative release rate of CBZ at pH 4.5 was 1.74 times higher than that in a neutral environment. In addition, we found that the contact angle of the CBZ@AP5/MSe⊃MO in maize and rape leaves was effectively decreased, which could retain more in the leaves after washout. It can also decrease the dry biomass and the reducing sugar of S.sclerotiorum. The CBZ@AP5/MSe⊃MO holds a good safety profile for plants, animal cells, and the environment owing to the targeted release properties. These results suggest that CBZ@AP5/MSe⊃MO is an environmentally friendly and effective drug-loaded system against S. sclerotiorum. It provides a new strategy for the design and development of nanopesticides and the control of S. sclerotiorum.

Dissipation, uptake, translocation and accumulation of five phthalic acid esters in sediment-Zizania latifolia system

The dissipation, uptake, translocation and accumulation of phthalic acid esters (PAEs) including diallyl phthalate (DAP), diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP) and di-(2-ethylhexyl) phthalate (DEHP) in sediment-Zizania latifolia system were investigated by gas chromatography-flame ionization detector after a QuEChERS pretreatment method. The dissipation rates of PAEs in sediment were positively correlated with exposure time, and more than 68.12% of PAEs in sediment were decreased after 28 d even when the spiked contents were extremely high. All the five PAEs could be taken up by roots from contaminated sediment and subsequently be transported into stems and leaves. There were significant linear correlations between the sediment content and the content in each tissue. DEHP was most readily transported from sediment to roots and stems, followed by BBP, DBP, DIBP and DAP, whereas the order of transportation from roots to leaves was reversed. During 28 d of exposure, the average concentration of each PAE in stems was the highest, followed by roots, leaves and edible parts. DEHP and BBP were the major contaminants in edible parts but could not pose a risk to human health. The accumulation of PAEs in edible parts was influenced by the species and concentration of PAEs as well as the survival time and harvest time of edible parts. The differences in uptake and translocation behaviors among PAEs in plant tissues were significantly correlated to their physicochemical properties, such as alkyl chain length and octanol/water partition coefficient (logK_ow). The results reveal that Zizania latifolia is not only a kind of safe food, but also a potential plant to remediate contaminated sediment by accumulating and degrading PAEs from the habitats.

Selenium Improved Phenylacetic Acid Content in Oilseed Rape and Thus Enhanced the Prevention of Sclerotinia sclerotiorum by Dimethachlon

Sclerotinia sclerotiorum is a broad-spectrum necrotrophic phytopathogen that can infect many plant species worldwide. The application of fungicides is a common measure for controlling Sclerotinia sclerotiorum. Due to the risk of developing resistance to fungicides, it is imperative to find ways to be environmentally friendly and even effective. Using bioactive compounds in plants to reduce the amounts of fungicides has become a clean and sustainable strategy of controlling Sclerotinia sclerotiorum. Our study found that selenium in soil mediated the phenylacetic acid-related metabolic pathway in oilseed rape and reduced the incidence rate of Sclerotinia sclerotiorum. The growth-inhibition rates of Sclerotinia sclerotiorum were observed at 25.82%, 19.67%, and 52.61% for treatments of 0.8 mg·L-1 dimethachlon, 0.1 mg·mL-1 phenylacetic acid, and dimethachlon (0.8 mg·L-1) + phenylacetic acid (0.1 mg·mL-1), respectively. Phenylacetic acid reduced the application amount of dimethachlon and enhanced the inhibition effect for Sclerotinia sclerotiorum. Results also suggested that phenylacetic acid severely damaged the morphological structure, changed the electrical conductivity, and reduced the capacity of acid production and oxalic acid secretion of Sclerotinia sclerotiorum mycelium. Further studies revealed that phenylacetic acid increased the gene-expression level of Ssodc1, Ssodc2, CWDE2 and CWDE10 in mycelium while decreasing the expression level of SsGgt1, and phenylacetic acid + dimethachlon reduced the relative expression level of SsBil. These findings verified that phenylacetic acid could partially replace the amount of dimethachlon, as well as enhance the prevention of Sclerotinia sclerotiorum by dimethachlon, which provides evidence for developing an environment-friendly method for Sclerotinia sclerotiorum control.

Selenium in Soil-Plant-Microbe: A Review

Selenium (Se) plays an important role in geochemistry and is an essential trace element for humans and animals. This review summarizes the transformation and accumulation of Se in the plant-soil-microbe system. As one of the important reservoirs of Se, soil is an important material basis of its entry into the food chain through plants. Soil with an appropriate amount of Se is beneficial for plant growth and plays a valuable role in a stress-resistant environment. Among the many migration and transformation pathways, the transformation of Se by microorganisms is particularly important and is the main form of Se transformation in the soil environment. In this review, the role and form transformation of Se in plants, soil, and microorganisms; the role of Se in plants; the form, input, and output of Se in soil; the absorption and transformation of Se by plants; and the role of microorganisms in Se transformation are presented. In addition to describing the migration and transformation laws of Se in the environment, this review expounds on the main directions and trends of Se research in the agricultural field as well as current gaps and difficulties in Se-related research. Overall, this reviews aims to provide necessary information and theoretical references for the development of Se-rich agriculture.

Soil applied Ca, Mg and B altered phyllosphere and rhizosphere bacterial microbiome and reduced Huanglongbing incidence in Gannan Navel Orange

Huanglongbing (HLB) caused by 'Ca. Liberibacter. Asiaticus (Clas)' is one of the destructive diseases for citrus, threatening the development of citrus industry. Adopting a proper fertilization method instead of using pesticides seems particularly important, which would contribute to a sustainable development of orchard. In this study, the impact of soil application of nutrients combined with foliar spray of macro- and micro-nutrients on the incidence of HLB and the phyllosphere and rhizosphere bacterial microbiome was investigated in Gannan Navel Orange orchard from 2015 to 2018. Compared with the control (T1), the yield of Gannan Navel Orange in all other treatments applied with macro- and micro-nutrients increased significantly in 2018 (by 20.5%-45.8%), but not in the first two years (2016-17). Among treatments, Ca + Mg + B application in soil (T2) showed the highest yield and lowest HLB incidence. According to the PCR results, CLas was negative in T2 but positive in the control, which directly proved HLB incidence was reduced with Ca + Mg + B application in soil. Moreover, 16S rRNA sequencing was used to characterize rhizosphere and phyllosphere microbial communities. Results showed that microbial biodiversity was increased and microbial community structure was altered in T2 treatment, of which the beneficial bacteria were enriched in phyllosphere and rhizosphere. The results of PICRUSt showed that in T2 treatment, rhizosphere microbe contained more membrane transport (ABC transporters) genes, while, carbohydrate metabolism genes were enriched in the control rhizosphere due to HLB obstruct the photosynthetic metabolite transport. In summary, results indicated that macro- and micro-nutrients application improved the yield of Gannan Navel Orange and soil application of Ca + Mg + B reduced HLB incidence by altering microbial community structure and increasing microbial biodiversity. This study developed an environment-friendly way to reduce HLB incidence and improve the yield of citrus.

Metabolomics of Chlorophylls and Carotenoids: Analytical Methods and Metabolome-Based Studies

Chlorophylls and carotenoids are two families of antioxidants present in daily ingested foods, whose recognition as added-value ingredients runs in parallel with the increasing number of demonstrated functional properties. Both groups include a complex and vast number of compounds, and extraction and analysis methods evolved recently to a modern protocol. New methodologies are more potent, precise, and accurate, but their application requires a better understanding of the technical and biological context. Therefore, the present review compiles the basic knowledge and recent advances of the metabolomics of chlorophylls and carotenoids, including the interrelation with the primary metabolism. The study includes material preparation and extraction protocols, the instrumental techniques for the acquisition of spectroscopic and spectrometric properties, the workflows and software tools for data pre-processing and analysis, and the application of mass spectrometry to pigment metabolomics. In addition, the review encompasses a critical description of studies where metabolomics analyses of chlorophylls and carotenoids were developed as an approach to analyzing the effects of biotic and abiotic stressors on living organisms.

Microbes: a potential tool for selenium biofortification

Selenium (Se) is a component of many enzymes and indispensable for human health due to its characteristics of reducing oxidative stress and enhancing immunity. Human beings take Se mainly from Se-containing crops. Taking measures to biofortify crops with Se may lead to improved public health. Se accumulation in plants mainly depends on the content and bioavailability of Se in soil. Beneficial microbes may change the chemical form and bioavailability of Se. This review highlights the potential role of microbes in promoting Se uptake and accumulation in crops and the related mechanisms. The potential approaches of microbial enhancement of Se biofortification can be summarized in the following four aspects: (1) microbes alter soil properties and impact the redox chemistry of Se to improve the bioavailability of Se in soil; (2) beneficial microbes regulate root morphology and stimulate the development of plants through the release of certain secretions, facilitating Se uptake in plants; (3) microbes upregulate the expression of certain genes and proteins that are related to Se metabolism in plants; and (4) the inoculation of microbes give rise to the generation of certain metabolites in plants contributing to Se absorption. Considering the ecological safety and economic feasibility, microbial enhancement is a potential tool for Se biofortification. For further study, the recombination and establishment of synthesis microbes is of potential benefit in Se-enrichment agriculture.

Design, Synthesis, and Structure-Activity Relationship of Quinazolinone Derivatives as Potential Fungicides

Plant diseases caused by phytopathogenic fungi reduce the yield and quality of crops. To develop novel antifungal agents, we designed and synthesized eight series of quinazolinone derivatives and evaluated their anti-phytopathogenic fungal activity. The bioassay results revealed that compounds KZL-15, KZL-22, 5b, 6b, 6c, 8e, and 8f exhibited remarkable antifungal activity in vitro. Especially, compound 6c displayed the highest bioactivity against Sclerotinia sclerotiorum, Pellicularia sasakii, Fusarium graminearum, and Fusarium oxysporum, displaying appreciable IC₅₀ values (50% inhibitory concentration) of 2.46, 2.94, 6.03, and 11.9 μg/mL, respectively. A further mechanism interrogation revealed abnormal mycelia, damaged organelles, and changed permeability of cell membranes in S. sclerotiorum treated with compound 6c. In addition, the in vivo bioassay indicated that compound 6c possessed comparable curative and protective effects (87.3 and 90.7%, respectively) to the positive control azoxystrobin (89.5 and 91.2%, respectively) at 100 μg/mL concentration against S. sclerotiorum. This work validated the potential of compound 6c as a new and promising fungicide candidate, contributing to the exploration of potent antifungal agents.