Combination of irradiated chitosan and microbial agent to reduce downy mildew on grapevine cv. Thompson seedless.

Globally sustainable disease management ensuring high quality in grapes is in demand as it holds significant importance as a versatile fruit for consumption, winemaking, and production of various products such as grape juice, raisin, and grape-seed oil. The present paper reports a combination of nano-biotechnology as a promising strategy for enhancing plant health and fruit productivity in grapes combining Irradiated chitosan nanoparticles and bio-control agents. The Irradiated Chitosan with Bacillus subtilis and Trichoderma viridae and pesticides were evaluated for disease management. Percent disease index, percent disease control, and percent yield enhancement in Cymoxanil 8% + Mamcozeb 64% WP @ 0.2% treatment were as 17. 24%, 67.97% and 33.91% in 150 ppm Irradiated chitosan+B. subtilis were 19.83, 63.16, 30.41 and in Trichoderma 150 ppm Irradiated chitosan were 24.58, 54.33, and 27.40, respectively as compared to untreated crop with disease severity 53.84% PDI. Thus, irradiated chitosan and Bacillus subtilis elucidated a synergistic combination for residue-free efficient phytosanitary measures, which harnessed the strength of chitosan and bio-control agents for sustainable grape productivity. These findings will also pave the way for a deeper understanding of the synergistic interaction between Irradiated nanochitosan and bio-control agents for an eco-friendly and economically viable disease management strategy. The minimum temperature and morning relative humidity (RH I) had positive significance, with correlation coefficients of 0.484 and 0.485, respectively. The evening relative humidity (RH II) had a positive highly significant positive correlation coefficient of 0.664. Chitosan merits as a multiple stress tolerance enhancing agent that will further help in mitigating climate change adaptations in grapevines reducing reliance on chemical agro-inputs.

The pathogenicity of Plasmopara viticola: a review of evolutionary dynamics, infection strategies and effector molecules.

Oomycetes are filamentous organisms that resemble fungi in terms of morphology and life cycle, primarily due to convergent evolution. The success of pathogenic oomycetes lies in their ability to adapt and overcome host resistance, occasionally transitioning to new hosts. During plant infection, these organisms secrete effector proteins and other compounds during plant infection, as a molecular arsenal that contributes to their pathogenic success. Genomic sequencing, transcriptomic analysis, and proteomic studies have revealed highly diverse effector repertoires among different oomycete pathogens, highlighting their adaptability and evolution potential.The obligate biotrophic oomycete Plasmopara viticola affects grapevine plants (Vitis vinifera L.) causing the downy mildew disease, with significant economic impact. This disease is devastating in Europe, leading to substantial production losses. Even though Plasmopara viticola is a well-known pathogen, to date there are scarce reviews summarising pathogenicity, virulence, the genetics and molecular mechanisms of interaction with grapevine.This review aims to explore the current knowledge of the infection strategy, lifecycle, effector molecules, and pathogenicity of Plasmopara viticola. The recent sequencing of the Plasmopara viticola genome has provided new insights into understanding the infection strategies employed by this pathogen. Additionally, we will highlight the contributions of omics technologies in unravelling the ongoing evolution of this oomycete, including the first in-plant proteome analysis of the pathogen.

In Vitro Collection for the Safe Storage of Grapevine Hybrids and Identification of the Presence of Plasmopara viticola Resistance Genes.

This paper focuses on the creation of an in vitro collection of grapevine hybrids from the breeding program of the Kazakh Scientific Research Institute of Fruit Growing and Viticulture and investigates the presence of Plasmopara viticola resistance mediated by Rpv3 and Rpv12 loci. We looked at the optimization of in vitro establishment using either shoots taken directly from field-grown plants or from budwood cuttings forced indoors. We further screened for the presence of endophyte contamination in the initiated explants and optimized the multiplication stage. Finally, the presence of the resistance loci against P. viticola was studied. The shoots initiated from the field-sourced explants were the more effective method of providing plant sources for in vitro initiation once all plant accessions met the goal of in vitro establishment. The concentration of phytohormones and the acidity of the culture medium have a great effect on the multiplication rate and the quality of in vitro stock cultures. Out of 17 grapevine accessions, 16 showed the presence of single or combined resistance loci against P. viticola. The grapevine accessions identified as carrying Rpv3 and Rpv12 alleles represent important genetic resources for disease resistance breeding programs. These accessions may further contribute to the creation of new elite cultivars of economic interest.

Comparative transcriptome revealed the molecular responses of Aconitum carmichaelii Debx. to downy mildew at different stages of disease development.

BACKGROUND: Aconitum carmichaelii Debx. has been widely used as a traditional medicinal herb for a long history in China. It is highly susceptible to various dangerous diseases during the cultivation process. Downy mildew is the most serious leaf disease of A. carmichaelii, affecting plant growth and ultimately leading to a reduction in yield. To better understand the response mechanism of A. carmichaelii leaves subjected to downy mildew, the contents of endogenous plant hormones as well as transcriptome sequencing were analyzed at five different infected stages. RESULTS: The content of 3-indoleacetic acid, abscisic acid, salicylic acid and jasmonic acid has changed significantly in A. carmichaelii leaves with the development of downy mildew, and related synthetic genes such as 9-cis-epoxycarotenoid dioxygenase and phenylalanine ammonia lyase were also significant for disease responses. The transcriptomic data indicated that the differentially expressed genes were primarily associated with plant hormone signal transduction, plant-pathogen interaction, the mitogen-activated protein kinase signaling pathway in plants, and phenylpropanoid biosynthesis. Many of these genes also showed potential functions for resisting downy mildew. Through weighted gene co-expression network analysis, the hub genes and genes that have high connectivity to them were identified, which could participate in plant immune responses. CONCLUSIONS: In this study, we elucidated the response and potential genes of A. carmichaelii to downy mildew, and observed the changes of endogenous hormones content at different infection stages, so as to contribute to the further screening and identification of genes involved in the defense of downy mildew.

Deciphering the Enhancing Impact of Exogenous Brassinolide on Physiological Indices of Melon Plants under Downy Mildew-Induced Stress.

Melon (Cucumis melo L.) is a valuable horticultural crop of the Cucurbitaceae family. Downy mildew (DM), caused by Pseudoperonospora cubensis, is a significant inhibitor of the production and quality of melon. Brassinolide (BR) is a new type of phytohormone widely used in cultivation for its broad spectrum of resistance- and defense-mechanism-improving activity. In this study, we applied various exogenous treatments (0.5, 1.0, and 2.0 mg·L-1) of BR at four distinct time periods (6 h, 12 h, 24 h, and 48 h) and explored the impact of BR on physiological indices and the genetic regulation of melon seedling leaves infected by downy-mildew-induced stress. It was mainly observed that a 2.0 mg·L-1 BR concentration effectively promoted the enhanced photosynthetic activity of seedling leaves, and quantitative real-time polymerase chain reaction (qRT-PCR) analysis similarly exhibited an upregulated expression of the predicted regulatory genes of photosystem II (PSII) CmHCF136 (MELO3C023596.2) and CmPsbY (MELO3C010708.2), thus indicating the stability of the PSII reaction center. Furthermore, 2.0 mg·L-1 BR resulted in more photosynthetic pigments (nearly three times more than the chlorophyll contents (264.52%)) as compared to the control and other treatment groups and similarly upregulated the expression trend of the predicted key enzyme genes CmLHCP (MELO3C004214.2) and CmCHLP (MELO3C017176.2) involved in chlorophyll biosynthesis. Meanwhile, the maximum contents of soluble sugars and starch (186.95% and 164.28%) were also maintained, which were similarly triggered by the upregulated expression of the predicted genes CmGlgC (MELO3C006552.2), CmSPS (MELO3C020357.2), and CmPEPC (MELO3C018724.2), thereby maintaining osmotic adjustment and efficiency in eliminating reactive oxygen species. Overall, the exogenous 2.0 mg·L-1 BR exhibited maintained antioxidant activities, plastid membranal stability, and malondialdehyde (MDA) content. The chlorophyll fluorescence parameter values of F0 (42.23%) and Fv/Fm (36.67%) were also noticed to be higher; however, nearly three times higher levels of NPQ (375.86%) and Y (NPQ) (287.10%) were observed at 48 h of treatment as compared to all other group treatments. Increased Rubisco activity was also observed (62.89%), which suggested a significant role for elevated carbon fixation and assimilation and the upregulated expression of regulatory genes linked with Rubisco activity and the PSII reaction process. In short, we deduced that the 2.0 mg·L-1 BR application has an enhancing effect on the genetic modulation of physiological indices of melon plants against downy mildew disease stress.

Sensitivity of Plasmopara viticola to selected fungicide groups and the occurrence of the G143A mutant in Australian grapevine isolates.

BACKGROUND: Grapevine downy mildew, caused by Plasmopara viticola, is an economically important disease in Australia and worldwide. The application of fungicides is the main tool to control this disease. Frequent fungicide applications can lead to the selection of resistant P. viticola populations, which has negative impacts on the management of the disease. Identification of resistance and its prevalence is necessary to inform resistance management strategies. RESULTS: A total of 86 P. viticola isolates were collected between 2017 and 2022 from vineyards in 15 growing regions across Australia for four fungicide groups; phenylamide (PA, group 4), carboxylic acid amide (CAA, group 40), quinone outside inhibitor (QoI, group 11) and quinone outside inhibitor stigmatellin binding type (QoSI, group 45). Decreased phenotypic sensitivity was detected for all four groups, and resistance to metalaxyl-M (PA) and pyraclostrobin (QoI), was detected. Genetic analysis to detect the G143A (QoI) and G1105S (CAA) mutations using amplicon-based sequencing was performed for 239 and 65 isolates collected in 2014-2017 and 2017-2022, respectively. G143A was detected in 8% and 52% of isolates, respectively, with strong association to phenotypic resistance. However, G1105S was not detected in any isolates. CONCLUSION: Plasmopara viticola isolates in Australia with resistance to at least two fungicide groups have been detected, therefore it is necessary to adopt resistance management strategies where resistance has been detected. Vineyards should continue to be monitored to improve management strategies for downy mildew. © 2024 Society of Chemical Industry.

Investigation of Using Hyperspectral Vegetation Indices to Assess Brassica Downy Mildew.

Downy mildew caused by Hyaloperonospora brassicae is a severe disease in Brassica oleracea that significantly reduces crop yield and marketability. This study aims to evaluate different vegetation indices to assess different downy mildew infection levels in the Brassica variety Mildis using hyperspectral data. Artificial inoculation using H. brassicae sporangia suspension was conducted to induce different levels of downy mildew disease. Spectral measurements, spanning 350 nm to 1050 nm, were conducted on the leaves using an environmentally controlled setup, and the reflectance data were acquired and processed. The Successive Projections Algorithm (SPA) and signal sensitivity calculation were used to extract the most informative wavelengths that could be used to develop downy mildew indices (DMI). A total of 37 existing vegetation indices and three proposed DMIs were evaluated to indicate downy mildew (DM) infection levels. The results showed that the classification using a support vector machine achieved accuracies of 71.3%, 80.7%, and 85.3% for distinguishing healthy leaves from DM1 (early infection), DM2 (progressed infection), and DM3 (severe infection) leaves using the proposed downy mildew index. The proposed new downy mildew index potentially enables the development of an automated DM monitoring system and resistance profiling in Brassica breeding lines.

Monoglucoside versus Diglucoside Anthocyanin Evolution of Red Wine Produced Using a Fungus-Resistant Grape Cultivar (Downy Mildew and Powdery Mildew) under Oxidative Conditions.

The need to reduce the use of pesticides in viticulture is increasing the interest in wines produced using fungal-resistant grapevine varieties, which are characterized by relevant contents of both monoglucoside and diglucoside anthocyanins. Aging in wooden barrels induces oxygen permeation into wine, but little is known about diglucoside anthocyanin evolution. Cabernet cortis wine was subjected to addition of oxygen and oak chips, and the anthocyanin changes were followed for 1 month. Decreases of 90% total monoglucosides, 80% acylated monoglucosides, 65% diglucosides, and 90% acylated diglucosides were observed. Monoglucosides formed pyranoanthocyanins, and the lower steric hindrance favored their polymerization with flavanols. Instead, the decrease in diglucosides was correlated to the number of hydroxyl groups of ring B, indicating the predominant oxidation of aglycones. However, three flavonol-anthocyanin-diglucoside derivatives named (epi)catechin-ethyl-Mv-dihexoside, (epi)catechin-ethyl-Pn-dihexoside, and (epi)catechin-Mv-dihexoside A-type were identified in wine for the first time. These research findings are useful for tuning suitable oenological practices to stabilize the color of these wines (type of barrel, aging times, oxygenation practices) and lower the malvin content, which currently is recommended by the OIV at a maximum of 15 mg/L and is a critical issue for their commercialization.

Screening of Galician grapevine varieties by SNPs, phenotypic traits, and phytopathology.

The genetic erosion of the European grapevine diversity in the last century has promoted the conservation of varieties in germplasm banks to prevent their disappearance. The study of these varieties is necessary as it would allow the diversification of the wine market, as well as provide a source of genes to face new pathogens or climate constraints. In this work, the grapevine varieties preserved in the "Estación de Viticultura e Enoloxía de Galicia" (EVEGA) Germplasm Bank (Ourense, Spain) were widely characterized, combining ampelography, ampelometry, agronomy, and phytopathology. Moreover, genetic characterization was carried out through the analysis of 48 single-nucleotide polymorphisms (SNPs). A Bayesian analysis based on the SNP data was carried out to define the genetic structure of the EVEGA Germplasm Bank, which allowed the differentiation of two main reconstructed panmictic populations (RPPs), confirming previous results obtained based on microsatellite markers (SSRs). A great diversity between varieties was found for almost every parameter evaluated for ampelography, ampelometry, phytopatology, phenology, and berry quality. A principal component analysis (PCA) performed with these phenotypical data allowed discrimination among some groups of varieties included in different genetic populations. This study allowed us to evaluate the grapevine diversity maintained in the EVEGA Germplasm Bank and characterize varieties of potential value for breeding programs of interest for the Galician viticulture.

Rapid Detection of a Downy Mildew Pathogen, Peronospora destructor, in Infected Onion Tissues and Soils by Loop-Mediated Isothermal Amplification.

Downy mildew of onion caused by a soil-inhabiting water mold, Peronospora destructor, is one of the most devastating diseases that can destroy entire onion fields in a matter of days. In this study, we developed a loop-mediated isothermal amplification (LAMP) assay that allows for rapid detection of P. destructor by visual inspection. The internal transcribed spacer 2 region of P. destructor was used to design primer sets for LAMP reactions. The optimal temperature and incubation time were determined for the most efficient primer set. In the optimized condition, the LAMP assay exhibited at least 100 times more sensitivity than conventional PCR, detecting femtogram levels of P. destructor genomic DNA (gDNA). Detection of the pathogen from a small number of spores without gDNA extraction further confirmed the high sensitivity of the assay. For specificity, the LAMP assay was negative for gDNA of other fungal pathogens that cause various diseases on onion and oomycetes, whereas the assay was positive for gDNA extracted from onion tissues showing the typical downy mildew symptoms. Finally, we examined the efficacy of the LAMP assay in detection of P. destructor in soils. Soils collected from onion fields that had been contaminated with P. destructor were solarized for 60 days. Whereas the LAMP assay was negative for the solarized soils, we were able to detect P. destructor that oversummers in fields. The LAMP assay developed in this study enables rapid detection and diagnosis of downy mildew of onion in infected tissues and in soil.

Potential Biocontrol Microorganisms Causing Attenuated Pathogenicity in Plasmopara viticola.

A phenomenon of pathogenicity attenuation of Plasmopara viticola was consistently observed during its subculture on grape. To clarify the causes of attenuated pathogenicity of P. viticola, culturable microbes were isolated from the P. viticola mass (mycelia, sporangiophores, and sporangia) in each generation and tested for their biocontrol efficacies on grape downy mildew (GDM). The results showed that the incidence of GDM decreased with the increase in the number of subculture times on both vineyard-collected leaves and grape leaves from in vitro-grown seedlings. The number of culturable microbial taxa on the surface of P. viticola decreased, whereas the population densities of four specific strains (i.e., K2, K7, P1, and P5) increased significantly with the increase in subculture times. Compared with the control, the biocontrol efficacies of the bacterial strain K2 reached 87.5%, and those of both fungal strains P1 and P5 reached 100.0%. Based on morphological characteristics and molecular sequences, strains K2, P1, and P5 were identified as Curtobacterium herbarum, Thecaphora amaranthi, and Acremonium sclerotigenum, respectively, and these three strains survived very well and multiplied on the surface of P. viticola. As the number of times P. viticola was subcultured increased, all three of these strains became the predominant strains, leading to greater P. viticola inhibition, attenuated P. viticola pathogenicity, and effective GDM biological control. To the best of our knowledge, this is the first report of C. herbarum and T. amaranthi having biological control activity against GDM.

A new digital technology to reduce fungicide use in vineyards.

There is a growing demand for technologies able to decrease the environmental impact of agricultural activities without penalizing quali-quantitative characteristics of productions. In the case of viticulture, one of the key problems is represented by the spray drift during fungicide treatments. The diffusion in operational farming contexts of technologies based on variable-rate and recycling tunnel sprayers is often limited by their cost and, for the latter, by their size and lower maneuverability, representing clear disadvantages especially in case of small farms or in hilly and mountain areas. We present a new digital technology implemented in a mobile app that supports the reduction of both the number of treatments and the amount of fungicide distributed per treatment. The technology is based (i) on an alert system that prevents unneeded treatments in case of no risk of infection and (ii) on the quantification of the optimal amounts of active ingredients and dilution water based on the sprayer type/settings and on leaf area index values estimated with a common smartphone. An internal database allows to adjust (in case of need) the active ingredient dose to assure full compliance with product's legal requirements. In case of heterogeneity in leaf area index values inside the vineyard, prescription maps are generated. Results from a 2-year case study in a vineyard in northern Italy are shown, where the system allowed to reduce by 26.4 % and 27.4 % (mean of two years), respectively, the seasonal amounts of fungicides and dilution water, and by 43.8 % the copper content in must. The high usability of the technology proposed (just a common smartphone is needed) and the fact that it does not require updating the farm machine park highlights the suitability of the proposed solution for operational farming conditions, including premium wine production districts often characterized by small farms in hilly areas.

Effect of Cucurbit Host, Production Region, and Season on the Population Structure of Pseudoperonospora cubensis in Florida.

Pseudoperonospora cubensis, the causal agent of Cucurbit downy mildew (CDM), is one of the most important diseases affecting cucurbit production in the United States. This disease is especially damaging to Florida production areas, as the state is a top producer of many cucurbit species. In addition, winter production in central and south Florida likely serves as a likely source of P. cubensis inoculum for spring and summer cucurbit production throughout the eastern United States, where CDM is unable to overwinter in the absence of a living host. Over 2 years (2017 and 2018) and four seasons (spring 2017, spring 2018, fall 2017, and fall 2018), 274 P. cubensis isolates were collected from cucurbit hosts at production sites in south, central, and north Florida. The isolates were analyzed with 10 simple sequence repeat (SSR) markers to establish population structure and genetic diversity and further assigned to a clade based on a qPCR assay. Results of population structure and genetic diversity analyses differentiated isolates based on cucurbit host and clade (1 or 2). Of the isolates assigned to clade by qPCR, butternut squash, watermelon, and zucchini were dominated by clade 1 isolates, whereas cucumber isolates were split 34 and 59% between clades 1 and 2, respectively. Clade assignments agreed with isolate clustering observed within discriminant analysis of principal components (DAPC) based on SSR markers, although watermelon isolates formed a group distinct from the other clade 1 isolates. For seasonal collections from cucumber at each location, isolates were typically skewed to one clade or the other and varied across locations and seasons within each year of the study. This variable population structure of cucumber isolates could have consequences for regional disease management. This is the first study to characterize P. cubensis populations in Florida and evaluate the effect of cucurbit host and clade-type on isolate diversity and population structure, with implications for CDM management in Florida and other United States cucurbit production areas.

Underlying Mechanisms of the Hedgehog-Like Panicle and Filamentous Leaf Tissue Symptoms Caused by Sclerospora graminicola in Foxtail Millet.

Downy mildew caused by Sclerospora graminicola is a systemic infectious disease affecting foxtail millet production in Africa and Asia. S. graminicola-infected leaves could be decomposed to a state where only the veins remain, resulting in a filamentous leaf tissue symptom. The aim of the present study was to investigate how S. graminicola influences the formation of the filamentous leaf tissue symptoms in hosts at the morphological and molecular levels. We discovered that vegetative hyphae expanded rapidly, with high biomass accumulated at the early stages of S. graminicola infection. In addition, S. graminicola could affect spikelet morphological development at the panicle branch differentiation stage to the pistil and stamen differentiation stage by interfering with hormones and nutrient metabolism in the host, resulting in hedgehog-like panicle symptoms. S. graminicola could acquire high amounts of nutrients from host tissues through secretion of ß-glucosidase, endoglucanase, and pectic enzyme, and destroyed host mesophyll cells by mechanical pressure caused by rapid expansion of hyphae. At the later stages, S. graminicola could rapidly complete sexual reproduction through tryptophan, fatty acid, starch, and sucrose metabolism and subsequently produce numerous oospores. Oospore proliferation and development further damage host leaves via mechanical pressure, resulting in a large number of degraded and extinct mesophyll cells and, subsequently, malformed leaves with only veins left, that is, "filamentous leaf tissue." Our study revealed the S. graminicola expansion characteristics from its asexual to sexual development stages, and the potential mechanisms via which the destructive effects of S. graminicola on hosts occur at different growth stages.

CRISPR/Cas9 editing of Downy mildew resistant 6 (DMR6-1) in grapevine leads to reduced susceptibility to Plasmopara viticola.

Downy mildew of grapevine (Vitis vinifera), caused by the oomycete Plasmopara viticola, is an important disease that is present in cultivation areas worldwide, and using resistant varieties provides an environmentally friendly alternative to fungicides. DOWNY MILDEW RESISTANT 6 (DMR6) from Arabidopsis is a negative regulator of plant immunity and its loss of function confers resistance to downy mildew. In grapevine, DMR6 is present in two copies, named VvDMR6-1 and VvDMR6-2. Here, we describe the editing of VvDMR6-1 in embryogenic calli using CRISPR/Cas9 and the regeneration of the edited plants. All edited plants were found to be biallelic and chimeric, and whilst they all showed reduced growth compared with non-transformed control plants, they also had reduced susceptibility to P. viticola. Comparison between mock-inoculated genotypes showed that all edited lines presented higher levels of salicylic acid than controls, and lines subjected to transformation presented higher levels of cis-resveratrol than controls. Our results identify VvDMR6-1 as a promising target for breeding grapevine cultivars with improved resistance to downy mildew.

Comparative Analysis of Transcriptomics and Metabolomics Reveals Defense Mechanisms in Melon Cultivars against Pseudoperonospora cubensis Infection.

Melon (Cucumis melo L.) represents an agriculturally significant horticultural crop that is widely grown for its flavorful fruits. Downy mildew (DM), a pervasive foliar disease, poses a significant threat to global melon production. Although several quantitative trait loci related to DM resistance have been identified, the comprehensive genetic underpinnings of this resistance remain largely uncharted. In this study, we utilized integrative transcriptomics and metabolomics approaches to identify potential resistance-associated genes and delineate the strategies involved in the defense against DM in two melon cultivars: the resistant 'PI442177' ('K10-1') and the susceptible 'Huangdanzi' ('K10-9'), post-P. cubensis infection. Even in the absence of the pathogen, there were distinctive differentially expressed genes (DEGs) between 'K10-1' and 'K10-9'. When P. cubensis was infected, certain genes, including flavin-containing monooxygenase (FMO), receptor-like protein kinase FERONIA (FER), and the HD-ZIP transcription factor member, AtHB7, displayed pronounced expression differences between the cultivars. Notably, our data suggest that following P. cubensis infection, both cultivars suppressed flavonoid biosynthesis via the down-regulation of associated genes whilst concurrently promoting lignin production. The complex interplay of transcriptomic and metabolic responses elucidated by this study provides foundational insights into melon's defense mechanisms against DM. The robust resilience of 'K10-1' to DM is attributed to the synergistic interaction of its inherent transcriptomic and metabolic reactions.

Comparative Transcriptome Analysis between Resistant and Susceptible Pakchoi Cultivars in Response to Downy Mildew.

Downy mildew caused by the obligate parasite Hyaloperonospora brassicae is a devastating disease for Brassica species. Infection of Hyaloperonospora brassicae often leads to yellow spots on leaves, which significantly impacts quality and yield of pakchoi. In the present study, we conducted a comparative transcriptome between the resistant and susceptible pakchoi cultivars in response to Hyaloperonospora brassicae infection. A total of 1073 disease-resistance-related differentially expressed genes were identified using a Venn diagram. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed that these genes were mainly involved in plant-pathogen interaction, plant hormone signal transduction, and other photosynthesis-related metabolic processes. Analysis of the phytohormone content revealed that salicylic acid increased significantly in the resistant material after inoculation with Hyaloperonospora brassicae, whereas the contents of jasmonic acid, abscisic acid, and 1-aminocyclopropane-1-carboxylic acid decreased. Exogenous salicylic acid treatment also significantly upregulated Hyaloperonospora brassicae-induced genes, which further confirmed a crucial role of salicylic acid during pakchoi defense against Hyaloperonospora brassicae. Based on these findings, we suggest that the salicylic-acid-mediated signal transduction contributes to the resistance of pakchoi to downy mildew, and PAL1, ICS1, NPR1, PR1, PR5, WRKY70, WRKY33, CML43, CNGC9, and CDPK15 were involved in this responsive process. Our findings evidently contribute to revealing the molecular mechanism of pakchoi defense against Hyaloperonospora brassicae.

Fungicide-Saving Potential and Economic Advantages of Fungus-Resistant Grapevine Cultivars.

The high susceptibility of European grapevine cultivars to downy mildew (DM) and powdery mildew (PM) causes the intensive use of fungicides. Fungus-resistant cultivars (FRCs) with different resistance (R) loci have been bred and could play an important role in reducing plant protection treatments (PPTs). However, little information is available about the extent to which PPTs can be reduced in the field through the use of FRCs and the associated economic advantages. In this study, different strategies with reduced PPTs on FRCs were tested in field experiments. The results demonstrated that the number of PPTs can be reduced by 60 to 90%, resulting in reductions in applied copper and sulfur by 52 to 79% through the use of FRCs compared with susceptible cultivars, without affecting grape or plant health. The saving potential varied among years, depending on the type of R loci and climatic conditions. Furthermore, this study highlights that completely omitting PPTs in the cultivation of FRCs can result in PM or DM infections and possible loss of yield and fruit quality. In addition to the field experiments, a two-year observation of the performance of FRCs in commercial vineyards was undertaken, which highlighted not only the significant reduction in PPTs but also the financial savings that can be achieved through the use of FRCs.

Simultaneous editing of two DMR6 genes in grapevine results in reduced susceptibility to downy mildew.

The reduction of pesticide treatments is of paramount importance for the sustainability of viticulture, and it can be achieved through a combination of strategies, including the cultivation of vines (Vitis vinifera) that are resistant or tolerant to diseases such as downy mildew (DM). In many crops, the knock-out of Downy Mildew Resistant 6 (DMR6) proved successful in controlling DM-resistance, but the effect of mutations in DMR6 genes is not yet known in grapevine. Today, gene editing serves crop improvement with small and specific mutations while maintaining the genetic background of commercially important clones. Moreover, recent technological advances allowed to produce non-transgenic grapevine clones by regeneration of protoplasts edited with the CRISPR/Cas9 ribonucleoprotein. This approach may revolutionize the production of new grapevine varieties and clones, but it requires knowledge about the targets and the impact of editing on plant phenotype and fitness in different cultivars. In this work we generated single and double knock-out mutants by editing DMR6 susceptibility (S) genes using CRISPR/Cas9, and showed that only the combined mutations in VviDMR6-1 and VviDMR6-2 are effective in reducing susceptibility to DM in two table-grape cultivars by increasing the levels of endogenous salicylic acid. Therefore, editing both genes may be necessary for effective DM control in real-world agricultural settings, which could potentially lead to unwanted phenotypes. Additional research, including trials conducted in experimental vineyards, is required to gain a deeper understanding of DMR6-based resistance.

A Whole-Genome Assembly for Hyaloperonospora parasitica, A Pathogen Causing Downy Mildew in Cabbage (Brassica oleracea var. capitata L.).

Hyaloperonospora parasitica is a global pathogen that can cause leaf necrosis and seedling death, severely threatening the quality and yield of cabbage. However, the genome sequence and infection mechanisms of H. parasitica are still unclear. Here, we present the first whole-genome sequence of H. parasitica isolate BJ2020, which causes downy mildew in cabbage. The genome contains 4631 contigs and 9991 protein-coding genes, with a size of 37.10 Mb. The function of 6128 genes has been annotated. We annotated the genome of H. parasitica strain BJ2020 using databases, identifying 2249 PHI-associated genes, 1538 membrane transport proteins, and 126 CAZy-related genes. Comparative analyses between H. parasitica, H.arabidopsidis, and H. brassicae revealed dramatic differences among these three Brassicaceae downy mildew pathogenic fungi. Comprehensive genome-wide clustering analysis of 20 downy mildew-causing pathogens, which infect diverse crops, elucidates the closest phylogenetic affinity between H. parasitica and H. brassicae, the causative agent of downy mildew in Brassica napus. These findings provide important insights into the pathogenic mechanisms and a robust foundation for further investigations into the pathogenesis of H. parasitica BJ2020.