Control Of Plant Diseases Research Articles

Using metabolomics to explore the effects of epigenetic-modification strategies on the metabolites of Acanthus ilicifolius L. endophytic fungi against ovarian cancer

Ovarian cancer is a serious threat to women's health and safety. So far, people have discovered more than 130 small molecule compounds of natural origin for anti-tumor, of which approximately 50% are of microbial origin. The Acanthus ilicifolius L. species is primarily distributed in the Guangdong, Hainan, and Guangxi regions of China and grows in tidally accessible coastal areas. Recent studies have revealed that Acanthus ilicifolius L. extracts are endowed with a range of pharmacological properties, including anti-inflammatory, hepatoprotective, antioxidant, and antitumor activities. Endophytic fungi are commonly found in the healthy tissue and organs of medicinal plants. These fungi and the plants they inhabit form mutually beneficial symbiotic relationships. Endophytic fungi produce a series of secondary metabolites, with active substances having shown great economic value and applications prospects in drug research and development as well as for the biological control of plant diseases. Secondary metabolites production by endophytic fungi is regulated by specific gene clusters, and several techniques have been used to stimulate the secondary metabolic processes of fungi, including epigenetic-modification and OSMAC (one strain many compounds) strategies, co-culturing, and gene modification. Among these, epigenetic modification has been shown to be effective; this strategy involves the addition of small-molecule epigenetic modifiers to the culture medium, thereby activating silenced biosynthetic gene clusters without altering the DNA sequences of the fungi. This approach facilitates the expression of silenced genes in endophytic fungi, thereby increasing the number and diversity of secondary metabolites. Furthermore, it assists in overcoming the inhibition of microbial secondary-metabolite synthesis under laboratory conditions, and enhances silenced-gene expressions. The advent of novel analytical techniques and bioinformatics has provided a comprehensive, multifaceted, and holistic understanding of fungal metabolism through the development of metabolomics as a research platform. However, few studies have combined anti-ovarian cancer-activity screening with metabolomic approaches in the search for activity-differentiating metabolites from endophytic fungi under the intervention of epigenetic modifiers. Herein, we investigated the impact of epigenetic modifiers on the secondary metabolites of the endophytic Diaporthe goulteri fungus from Acanthus ilicifolius L. to determine their potential anti-ovarian cancer activities. Crude extracts were obtained by controlling three variables: the number of fermentation days, the type of epigenetic modifier, and its concentration, with activities screened using the CCK-8 (cell counting kit-8) method. Ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was subsequently employed for non-targeted metabolomic analysis. A multivariate statistical analysis model was constructed using principal component analysis and orthogonal partial least squares-discriminant analysis, which combines model and variable importance projection, with qualitative screening performed and significant changes (variable importance in the projection (VIP)≥1; P<0. 05) determined. Fifteen differential metabolites were identified in the fungal and epigenetic modification group, primarily comprising polyketides, amino acids, derivatives, alkaloids, and organic acids, including prenderol, glycine, valine, 2-ethylcaproic acid, rubratoxin B, finasteride, 6-silaspiro[5.5]undecane, 1-(2-nitrophenoxy)octane, heptadecene, 1-pentadecene, 11-ketoetiocholanolone, 3-(1-ethyl-1,3,3-trimethyl-2,3-dihydro-1H-inden-5-yl)butanal, N2-benzoylarginine, tabutrex, (3aR,6S,6aS)-6-(4-hydroxy-2-methoxy-2-butanyl)-4,4-dimethylhexahydro-1(2H)-pentalenone, and 8-aminoquinoline. The expressions of prenderol, 1-(2-nitrophenoxy)octane, 3-(1-ethyl-1,3,3-trimethyl-2,3-dihydro-1H-inden-5-yl)butanal, N2-benzoylarginine, and 8-aminoquinoline were downregulated, whereas the expressions of the remaining 10 substances were upregulated. Polyketides were the main components that exhibited higher expressions. This study showed that latent active differential metabolites can be searched by combining anti-ovarian cancer-activity screening with metabolomics analysis, thereby providing a reference for the further development of Acanthus ilicifolius L. resources and the subsequent targeted isolation of active compounds.

Biocontrol potential of Bevibacillus brevis HK544 for fungal plant diseases

Chemical fungicides have been widely used to control plant diseases caused by fungal pathogens. Still, the overuse of these fungicides has led to concerns about the hazards to humans, animals, and the environment and an increase in fungicide resistance. Interest in biocontrol agents with strong antimicrobial activity has significantly increased to counteract the escalating risks of chemical fungicides. Our previous study found that a soil-born microbe, Brevibacillus brevis HK544, exhibited a promising antifungal activity against a plant pathogen, Fusarium graminearum, with edeine B1 identified as the active compound. Herein, we extended our study to investigate the in vitro and in vivo antifungal spectrum of B. brevis HK544, including edeine B1, against various plant pathogenic fungi and evaluated the possibility that B. brevis HK544 could be used in combination with chemical fungicides to enhance the disease control efficacy. With an in vitro broad-spectrum antifungal activity, the B. brevis HK544 culture filtrate, culture broth, and metabolite edeine B1 exhibited a promising disease control efficacy against tomato gray mold and tomato late blight among the tested fungal diseases. Based on the in vitro antifungal activity against Botrytis cinerea, when edeine B1 was combined with various chemical fungicides, the highest average synergy score among the tested combinations was observed in the edeine B1 and benomyl combination. The co-application of the B. brevis HK544 culture filtrate and benomyl improved the disease control efficacy against gray mold disease, supporting the in vitro result. Taken together, our results show that B. brevis HK544 has potential as a biological control agent for controlling plant pathogenic fungi and also that B. brevis HK544 could be combined with chemical fungicides to enhance the efficacy of antifungal agents.

Edge-Cloud Remote Sensing Data-Based Plant Disease Detection Using Deep Neural Networks with Transfer Learning.

The identification and control of plant diseases have become increasingly complex as agricultural lands expand globally. Traditional manual methods of monitoring and diagnosing diseases are not feasible for large-scale farms. The complexity is further heightened by the heterogeneity of data types collected through remote sensing methods, such as images, videos, and sensor readings, which need to be processed in real-time. This paper introduces a novel EdgeCloud Remote Sensing architecture that utilizes Deep Neural Networks (DNNs) with Transfer Learning to enhance the detection of plant diseases using remote sensing data. The proposed system employs a Fuzzy Deep Convolutional Neural Network (FCDCNN) to process multimodal data collected from both edge nodes and satellite point clouds. Transfer learning allows the sharing of model weights between cloud and edge nodes, thus optimizing performance without requiring frequent retraining. Simulations show that the proposed system achieves a 98% detection accuracy and reduces processing time by 25% compared to existing methods. By distributing tasks between edge and cloud resources, the system is able to process large datasets effectively and improve disease detection performance on vast farmlands.

Grapevines grown from canes having spent 10 months in space: study of their downy mildew susceptibility

The control of plant diseases represents a significant challenge in agriculture, particularly with the current emphasis on reducing pesticide use, necessitating alternative approaches. Among them, resistant plant breeding programs offer a promising alternative. Considering the stressful conditions in space, space conditions emerge as an innovative method for advancing crop improvement. This study explored the unique potential of the International Space Station (ISS) environment to induce beneficial modifications in grapevine, resulting in plants with reduced susceptibility to diseases. Canes of two Vitis vinifera L. cultivars, Cabernet Sauvignon (CS) and Merlot (Me), have undergone a 10-month space journey on-board the ISS, while others stayed on Earth (Ground Control, GC). We conducted a 2-year analysis of the response to downy mildew (Plasmopara viticola) of plants developed from ISS and GC canes, called Mother plants. The disease development of progenies produced from Merlot Mother plants was also evaluated. A higher proportion of individuals with low-susceptibility was noted in the ISS Mother group compared to the controls for both cultivars. This trend was also observed for the Merlot progenies. Finally, 11% of Merlot individuals (Mother and progenies, and for the 2 years of study) were distributed in the low susceptibility class. This study suggests that grapevine canes exposure to ISS conditions resulted in an enhanced percentage of plants showing reduction of susceptibility to downy mildew.

Unravelling the Current Status of Rice Stripe Mosaic Virus: Its Geographical Spread, Biology, Epidemiology, and Management

Rice stripe mosaic virus (RSMV) belongs to the Cytorhabdovirus species in the Rhabdoviridae family. Recently, RSMV was widely spread in East Asia and caused severe yield losses. RSMV is transmitted by the planthopper vectors, Recilia dorsalis, Nephotettix virescens, and Nilaparvata lugens, that mostly affect rice. The adult vectors can hibernate, transmit the virus, lay eggs on rice plants, and, finally, multiply in subsequent generations, resulting in new infection outbreaks. RSMV-infected rice varieties display striped mosaicism, mild dwarfism, stiff and twisted leaves, delayed heading, short panicles with large unfilled grains, and yield reduction. In nature, the infection of multiple pathogens in the same host is widespread, which is defined as co-infection. It can be antagonistic or synergistic. Pathological synergistic effects between RSMV and other viruses can generate strains with new genetic characteristics, leading to unpredictable epidemiological consequences. After the first identification of RSMV in 2015, significant advancements in understanding the disease’s characteristics, symptoms, cycles, geographic distribution, potential vectors, and synergistic interaction, as well as its management strategies, were developed. To reduce the damage due to RSMV infection, many scientists have recommended pest control techniques to target adult vectors. It is also essential to confirm the actual time of monitoring, development of resistant varieties, and changes in cultivation systems. Due to the limitations of the conventional plant disease control technologies, improvements in efficiency and safety are in high demand. Therefore, to find efficient and environmentally safe controls to mitigate these challenges, reviews of research are the foremost step. In this review, we summarize the basic epidemiological information about the origin of RSMV and its infection symptoms in the field, synergistic interaction with viruses during co-transmission, yield losses, formulation of the disease cycle, and control strategies from several case studies. Finally, we recommend the formulation of the disease cycle and management strategies of RSMV infection.

Effectiveness and Genetic Control of Trichoderma spp. as a Biological Control of Wheat Powdery Mildew Disease.

Wheat powdery mildew (WPM) is one of the most devasting diseases that affects wheat yield worldwide. Few efforts have been made to control such a serious disease. An effective way to control WPM is urgently needed. Biological control is an effective way to control plant diseases worldwide. In this study, the efficiency of three different Trichoderma spp. in controlling WPM at the seedling growth stage was tested using 35 highly diverse wheat genotypes. Highly significant differences were found in WPM resistance among the four treatments, confirming the efficiency of Trichoderma in controlling WPM. Of the three species, T. asperellum T34 (T34) was the most effective species in controlling WPM, as it reduced the symptoms by 50.56%. A set of 196 wheat genotypes was used to identify the genetic control of the WPM resistance induced by T34. A total of 39, 27, and 18 gene models were identified to contain the significant markers under Pm, T34, and the improvement in powdery mildew resistance due to T34 (T34_improvement) conditions. Furthermore, no gene model was common between T34 and Pm, suggesting the presence of completely different genetic systems controlling the resistance under T34 and Pm. The functional annotation and biological process pathways of the detected gene models confirm their association with the normal and induced resistance. This study, for the first time, confirms the efficiency of T34 in controlling WPM and provides a deep understanding of the genetic control of induced and normal resistance to WPM.

Assessment of Trichoderma Species Isolated From Volcanic Soil of a Durian Field in Sisaket Province, Thailand for Plant Growth Promotion and Biocontrol Potential

Trichoderma species are ubiquitous saprophytic fungi commonly found in soil, with potential as fungal biocontrol agents for plant disease control and growth promotion. This research aimed to assess the attributes of Trichoderma sp. as plant growth promoters, focusing on nitrogen fixation, siderophore production, plant nutrient solubilization and indole-3-acetic acid production. Out of 19 isolates tested, 6 (T05, T19, T25, T27, T28 and T33) showed superior plant growth promotion abilities. These isolates were further evaluated for their capacity to enhance the germination of Khao Dawk Mali 105 rice seeds. Seeds were soaked in a suspension of conidia at a concentration of 1×1012 conidia/mL, and germination rates were measured. The germination rate ranged between 77.67 - 86.67 %, statistically significantly higher than the control rate of 33.33 %. Among the isolates, T05 exhibited the highest promotion of plant growth, evidenced by root length (7.27 cm), shoot length (8.50 cm), fresh weight (0.54 g) and dry weight (0.27 g), all significantly different from the control. Additionally, the potential of isolates to inhibit the fungal pathogen Colletotrichum sp. MN-3 was assessed using a dual culture method, with T35 showing the highest inhibition percentage (60.90 %). Morphological classification and nucleotide sequencing of the ITS1-5.8S-ITS2 region of rDNA gene identified the isolates as T. harzianum, T. reesei, T. asperellum and T. longibrachiatum. These findings underscore the effectiveness of Trichoderma sp. in promoting plant growth and suppressing plant pathogenic fungi. HIGHLIGHTSSix Trichoderma isolates (T05, T19, T25, T27, T28 and T33) exhibited superior plant growth promotion abilities. These isolates significantly enhanced germination rates of Khao Dawk Mali 105 rice seeds compared to the method. Among the isolates, T05 showed the greatest promotion of plant growth, as evidenced by root length, shoot length, fresh weight and dry weight. Trichoderma isolates demonstrated potential for inhibiting the fungal pathogen Colletotrichum sp. MN-3. Morphological classification divided the Trichoderma sp. into 4 groups, and species identification through nucleotide sequencing revealed T. harzianum, T. reesei, T. asperellum and T. longibrachiatum. GRAPHICAL ABSTRACT

Preparation of carboxymethylated curdlan oligosaccharides and application on plant disease control

Curdlan is produced by fermentation of microorganisms, which is an insoluble β-(1 → 3)-D-glucans. To better effectively utilize native curdlan, firstly, a derivative from curdlan, carboxymethylated curdlan (CMCD), with different degrees of substitution (DS) DS ∼ 0.20, DS ∼ 0.43 and DS ∼ 0.82 were prepared in this study. Carboxymethylation increases solubility in water more than native curdlan. Moreover, CMCDs were investigated to be hydrolyzed by CcGluE, an endo-β-1 → 3-glucanase and generated the degradation products were oligosaccharides with degrees of polymerization (DP) mainly ranging from 2 to 7. CcGluE also showed high thermal and pH stability when CMCD ∼ 0.43 was used as a substrate. Then these oligosaccharides generated by different CMCDs were applied to Arabidopsis and the activity in inducing defense responses were detected after being treated by the pathogen of Pseudomonas syringae pv tomato DC3000 (Pst DC3000). CMCD (DS ∼ 0.20) degradation oligosaccharide (CMCD ∼ 0.20 OS) pre-treatment was the just one that significantly enhanced the disease resistance to Pst DC3000, which is mediated by the salicylic acid (SA) signaling pathway in plants. The findings offer new insights into the application of curdlan, demonstrating that carboxymethylation enhances its solubility in water. Additionally, the oligosaccharide products derived from CMCD degradation show promising prospects for controlling plant diseases in agriculture.

The Potential of Microorganisms for the Control of Grape Downy Mildew-A Review.

Plasmopara viticola (Berk.et Curtis) Berl. Et de Toni is the pathogen that causes grape downy mildew, which is an airborne disease that severely affects grape yield and causes huge economic losses. The usage of effective control methods can reduce the damage to plants induced by grape downy mildew. Biocontrol has been widely used to control plant diseases due to its advantages of environmental friendliness and sustainability. However, to date, only a few comprehensive reviews on the biocontrol of grape downy mildew have been reported. In this review, we summarize the biological characteristics of P. viticola and its infection cycle, followed by a detailed overview of current biocontrol agents, including bacteria and fungi that could be used to control grape downy mildew, and their control effects. Furthermore, potential control mechanisms of biocontrol agents against grape downy mildew are discussed. Lastly, suggestions for future research on the biocontrol of grape downy mildew are provided. This review provides the basis for the application of grape downy mildew biocontrol.

RNA interference: a promising biotechnological approach to combat plant pathogens, mechanism and future prospects.

Plant pathogens and other biological pests represent significant obstacles to crop Protection worldwide. Even though there are many effective conventional methods for controlling plant diseases, new methods that are also effective, environmentally safe, and cost-effective are required. While plant breeding has traditionally been used to manipulate the plant genome to develop resistant cultivars for controlling plant diseases, the emergence of genetic engineering has introduced a completely new approach to render plants resistant to bacteria, nematodes, fungi, and viruses. The RNA interference (RNAi) approach has recently emerged as a potentially useful tool for mitigating the inherent risks associated with the development of conventional transgenics. These risks include the use of specific transgenes, gene control sequences, or marker genes. Utilizing RNAi to silence certain genes is a promising solution to this dilemma as disease-resistant transgenic plants can be generated within a legislative structure. Recent investigations have shown that using target double stranded RNAs via an effective vector system can produce significant silencing effects. Both dsRNA-containing crop sprays and transgenic plants carrying RNAi vectors have proven effective in controlling plant diseases that threaten commercially significant crop species. This article discusses the methods and applications of the most recent RNAi technology for reducing plant diseases to ensure sustainable agricultural yields.

Ralstonia solanacearum Infection Drives the Assembly and Functional Adaptation of Potato Rhizosphere Microbial Communities.

Bacterial wilt caused by Ralstonia solanacearum is a destructive disease that affects potato production, leading to severe yield losses. Currently, little is known about the changes in the assembly and functional adaptation of potato rhizosphere microbial communities during different stages of R. solanacearum infection. In this study, using amplicon and metagenomic sequencing approaches, we analyzed the changes in the composition and functions of bacterial and fungal communities in the potato rhizosphere across four stages of R. solanacearum infection. The results showed that R. solanacearum infection led to significant changes in the composition and functions of bacterial and fungal communities in the potato rhizosphere, with various microbial properties (including α,β-diversity, species composition, and community ecological functions) all being driven by R. solanacearum infection. The relative abundance of some beneficial microorganisms in the potato rhizosphere, including Firmicutes, Bacillus, Pseudomonas, and Mortierella, decreased as the duration of infection increased. Moreover, the related microbial communities played a significant role in basic metabolism and signal transduction; however, the functions involved in soil C, N, and P transformation weakened. This study provides new insights into the dynamic changes in the composition and functions of potato rhizosphere microbial communities at different stages of R. solanacearum infection to adapt to the growth promotion or disease suppression strategies of host plants, which may provide guidance for formulating future strategies to regulate microbial communities for the integrated control of soil-borne plant diseases.

Isolation of a novel Bacillus subtilis HF1 strain that is rich in lipopeptide homologs and has strong effects on the resistance of plant fungi and growth improvement of broilers.

Bacillus subtilis is an important probiotic microorganism that secretes a variety of antimicrobial compounds, including lipopeptides, which are a class of small molecule peptides with important application value in the fields of feed additives, food, biopesticides, biofertilizers, medicine and the biological control of plant diseases. In this study, we isolated a novel B. subtilis HF1 strain that is rich in lipopeptide components and homologs, has a strong antagonistic effect on a variety of plant fungi, and is highly efficient in promoting the growth of broilers. The live B. subtilis HF1 and its fermentation broth without cells showed significant inhibitory effects on 20 species of plant fungi. The crude extracts of lipopeptides in the fermentation supernatant of B. subtilis HF1 were obtained by combining acid precipitation and methanol extraction, and the lipopeptide compositions were analyzed by ultrahigh-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). The results showed that HF1 could produce 11 homologs of surfactin and 13 homologs of fengycin. Among the fengycin homologs, C13-C19 fengycin A and C15-C17 fengycin B were identified; among the surfactin homologs, C11-C17 surfactin A and C13-C16 surfactin B were characterized. C13 fengycin A, C11 surfactin A and C17 surfactin A were reported for the first time, and their functions are worthy of further study. In addition, we found that HF1 fermentation broth with and without live cells could be used as a feed additive to promote the growth of broilers by significantly increasing body weight up to 15.84%. HF1 could be a prospective strain for developing a biocontrol agent for plant fungal diseases and an efficient feed additive for green agriculture.

Cestrum tomentosum L.f. Extracts against Colletotrichum scovillei by Altering Cell Membrane Permeability and Inducing ROS Accumulation.

Chili pepper anthracnose, caused by Colletotrichum spp., is a significant biotic stress affecting chili fruits globally. While fungicide application is commonly used for disease management due to its efficiency and costeffectiveness, excessive use poses risks to human health and the environment. Botanical fungicides offer advantages such as rapid degradation and low toxicity to mammals, making them increasingly popular for sustainable plant disease control. This study investigated the antifungal properties of Cestrum tomentosum L.f. crude extracts (CTCE) against Colletotrichum scovillei. The results demonstrated that CTCE effectively inhibited conidia germination and germ tube elongation at 40 µg/ml concentrations. Moreover, CTCE exhibited strong antifungal activity against C. scovillei mycelial growth, with an EC50 value of 18.81 µg/ml. In vivo experiments confirmed the protective and curative effects of CTCE on chili pepper fruits infected with C. scovillei. XTT analysis showed that the CTCE could significantly inhibit the cell viability of C. scovillei. Mechanistic studies revealed that CTCE disrupted the plasma membrane integrity of C. scovillei and induced the accumulation of reactive oxygen species in hyphal cells. These findings highlight CTCE as a promising eco-friendly botanical fungicide for managing C. scovillei infections in chili peppers.

Two medicinal molecules Hydralazine and Isoniazid have the potential to control wheat crown rot by combing with a N-acetyltransferase FDB2

Fusarium pseudograminearum is the main pathogen that causes wheat crown rot (WCR), causing serious harm to wheat production. Wheat secretes Benzoxazolinones (Bxs) as fungicidins to prevent F. pseudograminearum infection. Fusarium Detoxification of Bx 2 (FDB2) can degrade Bx to non-fungitoxic N-(2-hydroxyphenyl) malonamic acid. Therefore, FDB2 may be a potential drug target for WCR.In the present study, the structure of FDB2 was determined using the molecular replacement method. The overall FDB2 structure displayed a typical N-acetyltransferase (NAT1) conformation. Unlike other NAT1s, the active site cleft is divided into two parts by a long loop (A135MSPYPDVRKNQA147). Hydralazine, Isoniazid, and 2,4′-dibromoacetanilide were screened out as potential inhibitors of FDB2 by structure alignment. Affinity measurements by MST showed that FDB2 prefers to combine Isoniazid and Hydralazine rather than its natural substrate, 2-aminophenol. Wheat seedling infection assays showed that Isoniazid and Hydralazine suppress F. pseudograminearum invasion in wheat. Our study found that Hydralazine and Isoniazid have the potential to control WCR. This article provides a new idea for the application of medicine, which has serious adverse effects, on plant disease control to reduce research costs and make obsolete drugs shine with vitality.

Antibacterial Properties of Plant Extracts against the Pathogen of Rosaceae Plants Erwinia amylovora

Erwinia amylovora is a devastating pathogen of plants of the family Rosaceae causing blight on the leaves, shoots, and flowers. Orchard trees suffer the most, however, other plants, like roses, strawberries, raspberries, and hawthorn, can also be affected. Due to the extreme use of chemicals for plant protection, alternatives like plant extracts have been studied recently. Some of the research shows a good potential to control plant diseases, however, only a symbolic number of plant species have been tested, and also, on a restricted number of pathogens. The information on the activity of plant extracts against E. amylovora is scarce. In this study, we prepared plant extracts from fifteen plant species and tested them against the plant pathogenic bacteria E. amylovora. The products were prepared by Soxhlet extraction with methanol and the following concentration according to an established procedure. The finished products were diluted and tested for antibacterial activity in different concentrations in vitro against seven reference strains of E. am¬ylovora, isolated from different hosts, such as pear, apple, quince, aronia, hawthorn, strawberry, and musk strawberry. Extracts from the roots of Geranium macrorrhizum and fruits of Chaenomeles sp. genotypes showed promising potentialities for further experiments on the control of E. amylovora.

Understanding the Diversity, Evolution, Ecology, and Applications of Mycoviruses.

Mycoviruses are widely distributed among various kinds of fungi. Over the past 10 years, more novel mycoviruses have been discovered with the use of high-throughput sequencing techniques, and research on mycoviruses has made fantastic progress, promoting our understanding of the diversity, classification, evolution, and ecology of the entire virosphere. Mycoviruses affect the biological and ecological functions of their hosts, for example, by suppressing or improving hosts' virulence and reproduction ability, and subsequently affect the microbiological community where their hosts live; hence, we may develop mycoviruses to regulate the health of environments, plants, animals, and human beings. In this review, we introduce recently discovered mycoviruses from fungi of humans, animals, plants, and environments, and their diversity, evolution, and ecological characteristics. We also present the potential application of mycoviruses by describing the latest progress on using mycoviruses to control plant diseases. Finally, we discuss the main issues facing mycovirus research in the future.

Regulatory mechanism of C4-dicarboxylates in cyclo (Phe-Pro) production

Cyclo (Phe-Pro) (cFP), a cyclic dipeptide with notable antifungal, antibacterial, and antiviral properties, shows great promise for biological control of plant diseases. Produced as a byproduct by non-ribosomal peptide synthetases (NRPS), the regulatory mechanism of cFP biosynthesis remains unclear. In a screening test of 997 Tn5 mutants of Burkholderia seminalis strain R456, we identified eight mutants with enhanced antagonistic effects against Fusarium graminearum (Fg). Among these, mutant 88’s culture filtrate contained cFP, confirmed through HPLC and LC-MS, which actively inhibited Fg. The gene disrupted in mutant 88 is part of the Dct transport system (Dct-A, -B, -D), responsible for C4-dicarboxylate transport. Knockout mutants of Dct genes exhibited higher cFP levels than the wild type, whereas complementary strains showed no significant difference. Additionally, the presence of exogenous C4-dicarboxylates reduced cFP production in wild type R456, indicating that these substrates negatively regulate cFP synthesis. Given that cFP synthesis is related to NRPS, we previously identified an NRPS cluster in R456, horizontally transferred from algae. Specifically, knocking out gene 2061 within this NRPS cluster significantly reduced cFP production. A Fur box binding site was predicted upstream of gene 2061, and yeast one-hybrid assays confirmed Fur protein binding, which increased with additional C4-dicarboxylates. Knockout of the Fur gene led to up-regulation of gene 2061 and increased cFP production, suggesting that C4-dicarboxylates suppress cFP synthesis by enhancing Fur-mediated repression of gene 2061.

Seed coating with biocontrol bacteria encapsulated in sporopollenin exine capsules for the control of soil-borne plant diseases

Coating seeds with biocontrol agents represents an effective approach for managing soil-borne plant diseases. However, improving the viability of biocontrol microorganisms on the seed surface or in the rhizosphere remains a big challenge due to biotic and abiotic stresses. In this work, we developed a microbial seed coating strategy that uses sporopollenin exine capsules (SECs) as carriers for the encapsulation of the biofilm-like biocontrol bacteria. SECs was extracted from camellia bee pollen, and then characterized by Fourier Transform infrared spectroscopy (FTIR), elemental analysis and thermal gravity analysis (TG). The Paenibacillus polymyxa ZF129, a biocontrol bacterium, was introduced into SECs using the vacuum-incubation method and characterized by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Notably, the ZF129 cell formed a biofilm-like structure inside the SECs, which enhanced their tolerance to acidic stress. As a proof of concept, we applied ZF129-loaded SECs to coat pak choi seeds using a straightforward plate-shaking technique. The coated seeds demonstrated a high control efficacy of up to 60.46 % against clubroot disease. Overall, this study sheds light on the application of SECs as promising carrier for the encapsulation of biofilm-like biocontrol bacteria, further augmenting the biocontrol functionality of microbial seed coating.

Assessment of Physico-Chemical Properties of Biogas Slurry as an Organic Fertilizer for Sustainable Agriculture

Chemical fertilizers have been extensively used for growing crops and controlling plant diseases, but they pose potential hazards to the environment, soil health, plants, and people. The current world situation highlights the need to implement eco-friendly agricultural practices for sustainable crop production. Using environmentally friendly manure, such as biogas slurry, can help reduce the negative effects of chemical fertilizers. Biogas slurry is an efficient waste material and organic fertilizer, making it an ideal supplement for sustainable crop production and waste management. An experiment was conducted at IARI, New Delhi, to explore the nutrient potential of biogas slurry. The main objective of this study was to assess biogas slurry's physico-chemical characteristics and nutrient contents. Samples of biogas slurry were collected in three replications and analyzed using standard methods for macro and micronutrients. The data revealed that biogas slurry has a pH of 7.2-8.5, EC of 1.06 to 1.12 dS/m, and organic carbon content of 41.7 to 45.8%. In terms of fertility, it contains significant amounts of nitrogen (1.98-2.17%), phosphorus (0.97 to 1.15%), and potassium (1.98 to 2.17%). Additionally, biogas slurry contains micronutrients such as Zn (0.023-0.027 ppm), Cu (0.005-0.009 ppm), Fe (0.32-0.38 ppm), and Mn (0.089-0.094 ppm). Statistical analysis using ANOVA and Post Hoc tests indicated that the mean data values among all three replications do not differ significantly. Therefore, it can be concluded that the nutritive value of biogas slurry is sufficient to reduce the reliance on chemical fertilizers in agriculture. It represents an optimal long-term organic remedy for developing fertile soil, ensuring enduring agricultural productivity, and mitigating the negative environmental impacts associated with waste management.

Exogenous Application of dsRNA—Inducing Silencing of the Fusarium oxysporum Tup1 Gene and Reducing Its Virulence

Fusarium oxysporum is a widespread soil-borne fungal pathogen that can infect various plants, causing wilt and root rot diseases. The root rot disease of Atractylodes macrocephala caused by F. oxysporum is among the most serious diseases associated with continuous cropping, significantly hindering its sustainable development. In this study, we aimed to investigate the effect of exogenous application of double-stranded RNA (dsRNA) on silencing the F. oxysporum Tup1 gene to reduce its virulence and to evaluate its potential application in controlling root rot disease in A. macrocephala. The Tup1 gene was amplified from the F. oxysporum genome, and different lengths of Tup1-dsRNA were designed and synthesized. The uptake of dsRNA by the fungus was verified using Tup1-dsRNA labeled with fluorescein, and in vitro dsRNA treatment experiments were conducted to assess its impact on the growth and virulence of F. oxysporum. Additionally, Tup1-dsRNA was applied to the roots of A. macrocephala to evaluate its effectiveness in controlling root rot disease. The experimental results showed that F. oxysporum could effectively uptake exogenously applied Tup1-dsRNA, significantly reducing Tup1 gene expression. All lengths of Tup1-dsRNA inhibited fungal growth and caused morphological changes in the fungal hyphae. Further plant experiments and Reverse Transcription Quantitative Polymerase Chain Reaction (RT-qPCR) analysis indicated that Tup1-dsRNA treatment significantly reduced the incidence of root rot disease in A. macrocephala, which was supported by the reduction in peroxidase (POD) and catalase (CAT) enzyme activities, malondialdehyde (MDA) content, and proline (Pro) levels in treated root tissues. This study demonstrated that exogenous dsRNA could reduce the virulence of F. oxysporum by silencing the Tup1 gene and effectively mitigate the root rot disease it causes in A. macrocephala. The successful application of Tup1-dsRNA provided strong evidence for the potential of RNA interference (RNAi) technology in plant disease control. Future research could further optimize the design and application of dsRNA to enhance its practical value in agriculture.