Cucumber Powdery Mildew Research Articles

A genome-wide association study reveals molecular mechanism underlying powdery mildew resistance in cucumber

BackgroundPowdery mildew is a disease with one of the most substantial impacts on cucumber production globally. The most efficient approach for controlling powdery mildew is the development of genetic resistance; however, few genes associated with inherent variations in cucumber powdery mildew resistance have been identified as of yet.ResultsIn this study, we re-sequence 299 cucumber accessions, which are divided into four geographical groups. A genome-wide association study identifies 50 sites significantly associated with natural variations in powdery mildew resistance. Linkage disequilibrium analysis further divides these 50 sites into 32 linkage disequilibrium blocks containing 41 putative genes. Virus-induced gene silencing and gene expression analysis implicate CsGy5G015960, which encodes a phosphate transporter, as the candidate gene regulating powdery mildew resistance. On the basis of the resequencing data, we generate five CsGy5G015960 haplotypes, identifying Hap.1 as the haplotype most likely associated with powdery mildew resistance. In addition, we determine that a 29-bp InDel in the 3′ untranslated region of CsGy5G015960 is responsible for mRNA stability. Overexpression of CsGy5G015960Hap.1 in the susceptible line enhances powdery mildew resistance and phosphorus accumulation. Further comparative RNA-seq analysis demonstrates that CsGy5G015960Hap.1 may regulate cucumber powdery mildew resistance by maintaining a higher H2O2 level through the depletion of multiple class III peroxidases.ConclusionsHere we identify a candidate powdery mildew-resistant gene in cucumber using GWAS. The identified gene may be a promising target for molecular breeding and genetic engineering in cucumber to enhance powdery mildew resistance.

Spinach flavonoid-rich extract: Unleashing plant defense mechanisms against cucumber powdery mildew

In response to the escalating demand for organic commodities, the exploration of non-chemical alternatives such as phytochemicals for plant disease management has gained momentum. This investigation focused on assessing the efficacy of a sustainable compound, Spinach Flavonoid-Rich Extract (SFRE), in mitigating cucumber powdery mildew (Podosphaera fusca) under controlled greenhouse conditions, and its potential in eliciting plant defense mechanisms at both biochemical and genetic levels. The application of SFRE resulted in a significant reduction in P. fusca disease severity, with a decrease of approximately 99%. High-Performance Liquid Chromatography (HPLC) analysis identified spinacetin as the dominant flavonoid in SFRE, with a concentration of 81.97 μg per 100 mg of the extract's dry weight. Furthermore, SFRE was found to induce systemic resistance in the infected seedlings, as evidenced by the upregulation of defense-related enzymes, including β-1,3-glucanase, chitinase, peroxidase, phenylalanine ammonia-lyase, and polyphenol oxidase, and the enhanced expression of β-1,3-glucanase, chitinase, and phenylalanine ammonia-lyase genes. In addition, SFRE application led to an accumulation of flavonoid/phenolic compounds and an enhancement in chlorophyll synthesis. A robust correlation was observed between phenolic compounds and the activities of defense enzymes, as well as the expression of the tested genes. This study substantiates that SFRE, as a reservoir of natural compounds, presents an effective and environmentally friendly alternative to chemical fungicides for P. fusca control, and could be incorporated into a comprehensive approach to managing cucumber powdery mildew through integrated disease management strategies.

Chitosan nanoparticle encapsulation of celery seed essential oil: Antifungal activity and defense mechanisms against cucumber powdery mildew

The objective of the current study was to explore the antifungal potential of celery seed essential oil (CSEO) in a nano-carrier system against Podosphaera fusca, the causal agent of cucumber powdery mildew. We assessed the physicochemical characterization of CSEO-loaded chitosan nanoparticles (CSEO-LCNPs) using dynamic light scattering, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. The successful loading of various concentrations of CSEO into chitosan nanoparticles (1:0, 1:0.25, 1:0.5, 1:0.75, and 1:1) has been verified. The particles exhibited a spherical shape, with an average diameter of 113 nm, and a negatively charged surface with a zeta potential of -31.5 mV. The Korsmeyer-Peppas model well described the release behavior of CSEO from nanoparticles. Additionally, we examined the defense mechanism, as well as biochemical/molecular responses following foliar treatment with CSEO-LCNPs. In vivo, results revealed that CSEO-LCNPs foliar application on the cucumber seedlings inoculated with P. fusca significantly reduced the disease severity of powdery mildew. Treatment with CSEO-LCNPs led to an increase in phenolic and flavonoid compounds, chlorophyll concentration, enzyme activities, and gene transcriptions in inoculated cucumber seedlings. In our study, we observed a positive correlation between antioxidant compounds and the defense-associated enzymes as well as their corresponding gene expressions. Our study underscores the potential of CSEO-LCNPs as an eco-friendly and effective solution for managing cucumber powdery mildew.

Ficus carica Linn leaves extract induces cucumber resistance to Podosphaera xanthii by inhibiting conidia and regulating enzyme activity

Cucumbers (Cucumis sativus L.) are highly susceptible to infection by powdery mildew (PM), resulting in a deterioration of cucumber quality. The utilization of chemical control measures can effectively control cucumber PM; however, it may potentially give rise to issues such as environmental pollution, compromised safety, and drug resistance. The urgent need for a green, secure, and efficient strategy to manage cucumber PM necessitates attention. The predominant fungal pathogen causing PM in cucumbers is Podosphaera xanthii (P. xanthii) in this study. The preventive and control efficacy of Ficus carica Linn leaf extract (FLE) against P. xanthii was investigated for the first time. The preventive experiments entail pre-infection spraying of FLE prior to the occurrence of P. xanthii, while the curative experiments involve post-outbreak spraying of FLE. After comprehensive consideration, the optimal approach was determined to be spraying the front of cucumber leaves with a concentration of 0.04 mg/mL FLE in order to effectively control P. xanthii in leaf disc bioassay. The lowest superposition rate from FLE and trisodium phosphate dodecahydrate was 12.86 %, indicating that the impact of FLE on the respiratory metabolism of P. xanthii conidia primarily operates through the hexose monophosphate pathway (HMP). The growth of P. xanthii conidia and mycelium can be inhibited or delayed by FLE. The application of FLE can effectively mitigated chlorophyll loss, suppressed the activities of peroxidase (POD) and polyphenol oxidase (PPO), as well as enhanced the activities of phenylalanine ammonia lyase (PAL), chitinase, and β- 1,3-glucanase. Furthermore, three representative enzyme genes, PAL, POD, and chitinase, were chosen for the purpose of validation. The results suggested that FLE has the ability to modulate the expression of relevant enzyme genes, with peak effects observed after 3–4 days of treatment. The findings offer theoretical support for the advancement of novel botanical pesticides aimed at controlling crop diseases.

Powdery mildew-induced changes in phyllosphere microbial community dynamics of cucumber.

As an important habitat for microorganisms, the phyllosphere has a great impact on plant growth and health, and changes in phyllosphere microorganisms are closely related to the occurrence of leaf diseases. However, there remains a limited understanding regarding alterations to the microbial community in the phyllosphere resulting from pathogen infections. Here, we analyzed and compared the differences in phyllosphere microorganisms of powdery mildew cucumber from three disease severity levels (0% < L1 < 30%, 30% ≤ L2 < 50%, L3 ≥ 50%, the number represents the lesion coverage rate of powdery mildew on leaves). There were significant differences in α diversity and community structure of phyllosphere communities under different disease levels. Disease severity altered the community structure of phyllosphere microorganisms, Rosenbergiella, Rickettsia, and Cladosporium accounted for the largest proportion in the L1 disease grade, while Bacillus, Pantoea, Kocuria, and Podosphaera had the highest relative abundance in the L3 disease grade. The co-occurrence network analysis of the phyllosphere microbial community indicated that the phyllosphere bacterial community was most affected by the severity of disease. Our results suggested that with the development of cucumber powdery mildew, the symbiotic relationship between species was broken, and the entire bacterial community tended to compete.

A severity estimation method for lightweight cucumber leaf disease based on DM-BiSeNet

Accurately estimating the severity of cucumber diseases is crucial for improving cucumber quality and minimizing economic losses. Deep learning techniques have shown promising results in automatically extracting disease image features for severity estimation. However, existing methods still face challenges in accurately estimating disease severity under complex backgrounds and achieving real-time performance.This paper presents a lightweight severity estimation method called DM-BiSeNet to address these challenges. The proposed method utilizes BiSeNet V2 as the base network and incorporates depthwise separable convolutional blocks to optimize the detail branch. A simplified MobileNet V3 network is also constructed to optimize the semantic branch. The model training process is accelerated using the AdamW optimizer. To evaluate the performance of DM-BiSeNet, a dataset consisting of cucumber powdery mildew and downy mildew disease images collected in natural scenes is utilized. Experimental results demonstrate that DM-BiSeNet achieves higher accuracy in severity estimation, with an R2 value of 0.9407 and an RMSE of 1.0680, outperforming the comparison methods. Moreover, DM-BiSeNet exhibits a complexity of 1.54 GFLOPs and is capable of reasoning 94 disease images per second.The proposed DM-BiSeNet model offers a lightweight and effective solution for accurate and rapid severity estimation of cucumber diseases under complex backgrounds. It provides a valuable technical tool for quantitative disease estimation, offering significant potential for practical applications.

Multiplex gene editing reveals cucumber MILDEW RESISTANCE LOCUS O family roles in powdery mildew resistance.

Powdery mildew (PM) is one of the most widespread and prevalent diseases that affects a wide range of crops. In cucumber (Cucumis sativus L.), previous forward genetic studies have identified MILDEW RESISTANCE LOCUS O 8 (CsMLO8) as necessary but alone insufficient for cucumber PM resistance (PMR) and suggested the involvement of other members of the CsMLO family. However, the function of other CsMLO family members in cucumber remains largely unknown. Here, we developed a highly efficient multiplex gene editing system in cucumber to generate a series of Csmlo mutants from all the 13 family members. Systematic analysis of these mutants revealed growth effects of these CsMLO family members on development and PMR. Importantly, we obtained the Csmlo1/8/11 triple mutant with complete resistance to PM. Transcriptome and proteome analysis of PM-resistant Csmlo mutants suggested that the kinesin-like calmodulin-binding protein (KCBP)-interacting Ca2+-binding protein (CsKIC), calmodulin-like protein 28 (CsCML28), and Ca2+-dependent protein kinase 11 (CsCPK11)-mediated calcium signaling pathway is involved in PMR. CsMLO8 interacted directly with CsKIC, and the simultaneous silencing of both genes resulted in a phenotype that resembled the silencing of CsKIC alone. Silencing CsCML28 and CsCPK11 increased susceptibility to PM, whereas overexpressing CsCPK11 through genetic transformation enhanced cucumber's PMR, demonstrating their positive regulatory roles in PMR. Given the importance of PMR for cucurbit crops, this research provides unprecedented insights into the function of the proteins encoded by the CsMLO gene family as well as the plant defense response to PM pathogen.

Efficacy of fungicides against powdery mildew of cucumber (Cucumis sativus L.)

Efficacy of fungicides against powdery mildew of cucumber (Cucumis sativus L.)

Defense Mechanisms Induced by Celery Seed Essential Oil against Powdery Mildew Incited by Podosphaera fusca in Cucumber.

This study aimed to evaluate the effectiveness of essential oil extracted from celery (Apium graveolens) seeds (CSEO) for the control of powdery mildew of cucumber (Cucumis sativus) incited by Podosphaera fusca and to investigate the metabolic and genetic defense mechanisms triggered by the treatment with this essential oil in cucumber seedlings. The main compounds in the CSEO as determined by gas chromatography-mass spectrometry (GC-MS) analysis were d-limonene, 3-butyl phthalide, β-selinene, and mandelic acid. The treatment with CSEO led to an increase in the content of both chlorophyll and phenolic/flavonoid compounds in cucumber leaves. In greenhouse tests, the application of CSEO reduced by 60% the disease severity on leaves of cucumber plants and stimulated the activity of defense-related enzymes such as β-1,3-glucanase, chitinase, phenylalanine ammonia-lyase, peroxidase, and polyphenol oxidase. Moreover, treatment with CSEO induced overexpression of β-1,3-glucanase, chitinase, and phenylalanine ammonia-lyase genes. A highly significant correlation was found between the β-1,3-glucanase, chitinase, and phenylalanine ammonia-lyase enzymatic activities and the relative expression of the corresponding encoding genes in both inoculated and non-inoculated cucumber seedlings treated with the essential oil. Overall, this study showed that CSEO is a promising eco-friendly candidate fungicide that can be exploited to control cucumber powdery mildew.

Detection Method of Fungal Spores Based on Fingerprint Characteristics of Diffraction-Polarization Images.

The most significant aspect of promoting greenhouse productivity is the timely monitoring of disease spores and applying proactive control measures. This paper introduces a method to classify spores of airborne disease in greenhouse crops by using fingerprint characteristics of diffraction-polarized images and machine learning. Initially, a diffraction-polarization imaging system was established, and the diffraction fingerprint images of disease spores were taken in polarization directions of 0°, 45°, 90° and 135°. Subsequently, the diffraction-polarization images were processed, wherein the fingerprint features of the spore diffraction-polarization images were extracted. Finally, a support vector machine (SVM) classification algorithm was used to classify the disease spores. The study's results indicate that the diffraction-polarization imaging system can capture images of disease spores. Different spores all have their own unique diffraction-polarization fingerprint characteristics. The identification rates of tomato gray mold spores, cucumber downy mold spores and cucumber powdery mildew spores were 96.02%, 94.94% and 96.57%, respectively. The average identification rate of spores was 95.85%. This study can provide a research basis for the identification and classification of disease spores.

β-Aminobutyric Acid and Powdery Mildew Infection Enhanced the Activation of Defense-Related Genes and Salicylic Acid in Cucumber (Cucumis sativus L.).

Powdery mildew disease, caused by Sphaerotheca fusca, is a major disease affecting cucumbers cultivated in greenhouses. This study was conducted to find defense genes induced by β-aminobutyric acid (BABA) and powdery mildew in cucumber. Disease severities of 25% and 5% were exhibited by the 2000 and 5000 mg/L BABA-treated cucumber, respectively. BABA did not affect the spore germination of the powdery mildew pathogen, showing that BABA is not an antifungal agent against the pathogen. In quantitative real-time PCR analysis, BABA-treated cucumber upregulated the transcriptional levels of the defense genes CsPAL, CsPR3, CsPR1, CsLOX1, CsLOX23, Cs LecRK6.1, CsWRKY20, and Cupi4 in cucumber to maximum levels at 48 h, whereas CsLecRK6.1 reached maximum expression after 24 h, and further, salicylic acid (SA) levels were significantly increased in BABA-treated cucumber plants. In addition, the cucumber infected with powdery mildew underwent a 1.6- to 47.3-fold enhancement in the defense genes PAL, PR3, PR1, Lox1, Lox 23, LecRK6.1, WRKY20, and Cupi4 compared to heathy cucumber. These results suggest that the BABA-induced defense response is associated with SA signaling pathway-dependent systemic acquired resistance (SAR) in cucumber, which is involved in plant resistance mechanisms.

Structure-Based Discovery of New Succinate Dehydrogenase Inhibitors via Scaffold Hopping Strategy.

Scaffold hopping strategy has become one of the most successful methods in the process of molecular design. Seeking to develop novel succinate dehydrogenase inhibitors (SDHIs), we employed a scaffold hopping strategy to design compounds featuring geminate dichloralkenes (gem-dichloralkenes) fragment. After stepwise modifications, a series of N-cyclopropyl-dichloralkenes-pyrazole-carboxamide derivatives was synthesized. Among them, compounds G28 (IC50 = 26.00 nM) and G40 (IC50 = 27.00 nM) were identified as the best inhibitory activity against porcine SDH, with IC50 values reaching the nanomolar range, outperforming the lead compound pydiflumetofen. Additionally, the greenhouse assay indicated that compounds G37 (EC90 = 0.031 mg/L) and G34 (EC90 = 1.67 mg/L) displayed extremely high activities against wheat powdery mildew (WPM) and cucumber powdery mildew (CPM), respectively. Computational results further revealed that the gem-dichloralkene fragment and fluorine substituted pyrazole form an extra hydrophobic interaction and dipolar-dipolar interaction with SDH. In summary, our study provides a novel gem-dichloralkene scaffold with outstanding fungicidal properties, obtained through scaffold hopping, that holds great potential for future research on PM control.

Relative biochemical and physiological docking of cucumber varieties for supporting innate immunity against Podosphaera xanthii

Powdery mildew in cucumber is caused by the Podosphaera xanthii. No strategy for improving disease resistance can be successful in the absence of thorough insights into the physiological and biochemical responses of cucumber plants to powdery mildew. Therefore, a field experiment was executed to evaluate five commercial cucumber varieties (V1: Dynasty, V2: Long green, V3:Desi Kheera, V4:Thamin II, V5:Cucumber 363) for their inherent immunity to powdery mildew. Upon inoculating cucumber plants with Podosphaera xanthii, we noted differential responses among the varieties. Compared to other varieties, V1 and V2 showed higher values (P ≤ 0.05) for chlorophyll-a under control and pathogen-attacked plants respectively. The minimum value of anthocyanin content (−53.73%) was recorded in V3 as compared to other varieties post pathogen infection. All pathogen-infected cucumber varieties showed a considerable (P ≤ 0.05) loss in flavonoid content except V2. The maximum destruction for Phenolics under powdery mildew (179%) were recorded in V4, whereas V1 exhibited maximum phenolic content under control conditions. In pathogen-infected plants, the minimum AsA was recorded in V5 as compared to all other varieties. Pathogen invasion impacted significantly (P ≤ 0.05) the activity of superoxide dismutase (SOD). Besides, cucumber plants after pathogen inoculation resulted in a considerable (P ≤ 0.05) increase of peroxidase (POD) activity in V1 (5.02%), V2 (7.5%), and V3 (11%) in contrast to V4. Our results confirmed that cucumber varieties perform differently, which was brought on by distinct metabolic and physiological modifications that have an impact on growth and development. The changes in different attributes were correlated with cucumber resistance against powdery mildew. The results would help us fully harness the potential of these varieties to trigger disease management initiatives and defense responses.

Entomopathogenic fungus Beauveria bassiana-based bioinsecticide suppresses severity of powdery mildews of vegetables by inducing the plant defense responses.

The entomopathogenic fungus Beauveria bassiana is used commercially as a microbial insecticides against a wide range of agricultural insect pests. Some strains of B. bassiana protect the plants from pathogens, but the underlying mechanisms are largely unknown. Here, we found that prophylactic sprays of commercial bioinsecticide Botanigard on cucumber, tomato, and strawberry plants suppressed the severity of economically damaging powdery mildews. On leaf surfaces, hyphal elongation and spore germination of cucumber powdery mildew, Podosphaera xanthii, were inhibited, but B. bassiana strain GHA, the active ingredient isolated from Botanigard, only inhibited hyphal elongation but had no effect on spore germination of P. xanthii. In addition, strain GHA suppressed powdery mildew symptoms locally, not systemically. Treatment with Botanigard and strain GHA induced a hypersensitive response (HR)-like cell death in epidermal cells of the cucumber leaves in a concentration-dependent manner and inhibited penetration by P. xanthii. Transcriptome analysis and mass spectrometry revealed that GHA induced expression of salicylic acid (SA)-related genes, and treatment with Botanigard and GHA increased the SA level in the cucumber leaves. In NahG-transgenic tomato plants, which do not accumulate SA, the biocontrol effect of tomato powdery mildew by GHA was significantly reduced. These results suggested that B. bassiana GHA induces SA accumulation, leading to the induction of HR-like cell death against powdery mildew and subsequent suppression of fungal penetration. Thus, Botanigard has the potential to control both insect pests and plant diseases.

Evaluating the Efficacy of the Fermentation Formula of Bacillus velezensis Strain Tcb43 in Controlling Cucumber Powdery Mildew

Powdery mildew is a prevalent disease that affects cucumber crops, leading to yield reductions and declines in quality. Bacillus sp. strain Tcb43 culture medium was shown to be capable of inhibiting fungal spore germination in previous reports. In this study, the identification of the Tcb43 strain was updated to Bacillus velezensis by using whole-genome sequencing. The strain exhibited tolerance to a wide range of temperatures (12–40 °C), salinities (7–10%), and pH levels (ranging from 5 to 11). Additionally, Tcb43 demonstrated insensitivity to most tested fungicides. A new fermentation formula, Tcb43FBSO, was developed by adding 0.25% soybean oil to the fermented formula (Tcb43FB). This new formula exhibited a shelf life of up to 12 months with the decrease in bacterial count from 5.35 × 108 to 1.97 × 108 cfu/mL. Greenhouse assays showed that the treatment of potted cucumber plants with a 100-fold dilution (100×) of Tcb43FBSO for four weeks resulted in a significant reduction (64.64%) of cucumber powdery mildew compared to the mock group. In large-scale greenhouse trials, the treatment of cucumber plants with 200× of Tcb43FBSO for 5 weeks effectively suppressed powdery mildew disease, with a control rate that reached 76.6% compared to the mock group. These findings highlight the potential of Tcb43 as a biocontrol agent for managing cucumber powdery mildew and suggest its promising application in agriculture.

Genetics, resistance mechanism, and breeding of powdery mildew resistance in cucumbers (Cucumis sativus L.)

Cucumber is an important vegetable worldwide, and powdery mildew (PM) is a common and serious disease of cucumbers. Breeding disease-resistant cucumber varieties is the most advantageous strategy to control this disease. In recent years, exploration and identification of cucumber PM resistance genes have achieved great advancement, and many genes have been cloned and verified using different methods. However, the resistance mechanism of cucumber PM is still unclear, and many ambiguities need to be elucidated urgently. In this review, we summarized the research advances in PM resistance in cucumbers, including genetic analysis, quantitative trait locus mapping, map-based cloning, transcriptomics, mlo-mediated PM resistance, and mining of noncoding RNAs involved in resistance. Finally, the research directions and the problems that need to be solved in the future were discussed.

Fungicidal spectrum and biological properties of a new fungicide, pyriofenone.

Pyriofenone is a new fungicide developed by Ishihara Sangyo Kaisha, Ltd. To determine the fungicidal spectrum of pyriofenone, in vivo pot tests and in vitro mycelial growth-inhibition tests were conducted. Pyriofenone showed excellent activity against wheat and cucumber powdery mildew and moderate efficacy against rice blast in the pot tests. In the mycelial growth-inhibition tests, most fungi were not affected by pyriofenone except for Botrytis cinerea, Helminthosporium sacchari, Pseudocercosporella herpotrichoides, Pyricularia oryzae, Rosellinia necatrix, and Verticillium dahliae. The fungicidal properties of pyriofenone on powdery mildew in cucumber and wheat were evaluated precisely. Pyriofenone exhibited excellent preventive and residual activities. It had high rainfastness in the cucumber leaves against powdery mildew. Pyriofenone also showed inhibitory activity on lesion development upon application until 2 days after inoculation, and the lesion expansion and sporulation of the cucumber powdery mildew fungus were effectively controlled. Furthermore, pyriofenone showed translaminar and vapor activities.

"H" sprayer effect on liquid deposition on cucumber leaves and powdery mildew prevention in the shed.

To clarify the effect of droplet size on solution deposition and powdery mildew control on greenhouse cucumber leaves, the effect of volume median droplet diameter (VMD) on solution deposition and maximum retention, as well as the effect of flusilazole on powdery mildew control on cucumber, was determined using the stem and leaf spray method. The VMD of the typical fan nozzles (F110-01, F110-015, F110-02, F110-03) of the selected US Tee jet production differs by approximately 90 μm. The results showed that the deposition of flusilazole solution on cucumber leaves decreased as the VMD of the droplets increased and that the deposition of the solution in the treatments with VMD of 120, 172, and 210 μm decreased by 22.02%, 10.37%, and 46. 97%, respectively, compared to that observed with treatment with 151 μm VMD. The deposition of the solution on cucumber leaves showed the highest deposition efficiency of 63.3% when the applied solution volume was 320 L/hm2, and the maximum stable retention of the liquid on the leaves was 6.6 µl/cm2. The control effects of different concentrations of flusilazole solution on cucumber powdery mildew differed significantly, and the best control effect was achieved at the dosage of 90 g/hm2 of the active ingredient, which was 15%-25% higher than that observed at the dosage of 50 and 70 g/hm2 of the active ingredient per hectare. A significant difference in the effect of droplet size on the control of cucumber powdery mildew was observed at any specific liquid concentration. Nozzle F110-01 showed the best control effect when the dosage of the active ingredient was 50 and 70 g/hm2 per hectare, which did not differ significantly from that observed with nozzle F110-015 but differed significantly from those observed with nozzles F110-02 and F110-03. Hence, we concluded that the use of smaller droplets with VMD of 100-150 μm, i.e. the choice of F110-01 or F110-015 nozzles, for application on the leaf parts of cucumber in the greenhouse under conditions of high liquid concentration, can significantly improve the effective use of pharmaceuticals and the disease control effect.

Preparation of Trichoderma asperellum Microcapsules and Biocontrol of Cucumber Powdery Mildew.

Microencapsulation is an important technique for protecting the viability and activity of microorganisms under adverse environmental conditions. To improve biological control, controlled-release microcapsules of Trichoderma asperellum were prepared and embedded in combinations of the biodegradable wall materials sodium alginate (SA). The microcapsules were evaluated for their ability to control cucumber powdery mildew in the greenhouse. The results showed that the highest encapsulation efficiency of 95% was obtained by applying 1% SA and 4% calcium chloride. The microcapsules provided good, controlled release and UV resistance, and could be stored for a long time. The greenhouse experiment revealed that the T. asperellum microcapsules had a maximal biocontrol efficiency of 76% against cucumber powdery mildew. In summary, embedding T. asperellum in microcapsules is a promising technique to improve the survivability of T. asperellum conidia. The T. asperellum microcapsules exerted significant biocontrol efficiency against cucumber powdery mildew. IMPORTANCE Trichoderma asperellum is widely found in plant roots and soil and has been used for the biocontrol of various plant pathogens; however, the control efficiency of T. asperellum is usually unstable in field trials. To improve the control efficiency of T. asperellum, in the present study, T. asperellum microcapsules were prepared using sodium alginate as wall material to reduce the effects of temperature, UV irradiation, and other environmental factors on its activity, and to significantly improve its biocontrol efficiency on cucumber powdery mildew. Microcapsules can prolong the shelf life of microbial pesticides. This study provides a new way to prepare a biocontrol agent against cucumber powdery mildew with high efficiency.

A Complete Genome Sequence of Podosphaera xanthii Isolate YZU573, the Causal Agent of Powdery Mildew Isolated from Cucumber in China.

Podosphaera xanthii is a well-known obligate biotrophic pathogen that causes powdery mildew (PM) disease on cucurbitaceous plants and is one of the most important limiting factors for cucumber production worldwide. To better understand the avirulence effector proteins in this species that are known to be involved in host-pathogen interaction, the draft genome assembly of P. xanthii isolate YZU573 from cucumber leaves with symptoms of PM was obtained with a hybrid approach, combining nanopore long-read and llumina paired-end sequencing. The final P. xanthii YZU573 genome assembly of 152.7 Mb consists of 58 contigs, with an N50 value of 0.75 Mb and 6491 predicted protein-coding genes. The effector analysis using the whole-genome sequence information revealed a total of 87 putative effector candidates, and 65 of them had their analogs, whereas the remaining 22 were novel ones. The new P. xanthii genome provides valuable resources to better understand plant-microbe interaction in cucumber PM disease.