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In viticulture, downy mildew is one of the most common diseases that, if not adequately treated, can diminish production yield. However, the uncontrolled use of pesticides to alleviate its occurrence can pose significant risks for farmers, consumers, and the environment. This paper presents a new framework for the early detection and estimation of the mildew’s appearance in viticulture fields. The framework utilizes a protocol for the real-time acquisition of drones’ high-resolution RGB images and a cloud-docker-based video or image inference process using object detection CNN models. The authors implemented their framework proposition using open-source tools and experimented with their proposed implementation on the debina grape variety in Zitsa, Greece, during downy mildew outbursts. The authors present evaluation results of deep learning Faster R-CNN object detection models trained on their downy mildew annotated dataset, using the different object classifiers of VGG16, ViTDet, MobileNetV3, EfficientNet, SqueezeNet, and ResNet. The authors compare Faster R-CNN and YOLO object detectors in terms of accuracy and speed. From their experimentation, the embedded device model ViTDet showed the worst accuracy results compared to the fast inferences of YOLOv8, while MobileNetV3 significantly outperformed YOLOv8 in terms of both accuracy and speed. Regarding cloud inferences, large ResNet models performed well in terms of accuracy, while YOLOv5 faster inferences presented significant object classification losses.

The oomycete Plasmopara viticola, which causes downy mildew, is currently one of the most destructive pathogens affecting grape production. Although native to the eastern United States, P. viticola was introduced into Europe in the mid-to-late 1800s and is now found in virtually every grape-growing region of the world. Since its discovery, much effort has been made to understand the life cycle and infection process of the pathogen to develop more effective management practices. Widespread application of fungicides, especially those which have only one mode of action, has led to an increased occurrence of resistance to these treatments. Thus, with increased fungicide resistance and rising environmental concerns surrounding their use, traditional chemical management practices have begun to fall out of favor. Newer approaches, from targeted breeding utilizing quantitative trait loci to biological control agents, are continually being investigated and adapted to limit the damage caused by downy mildew. This review summarizes the current knowledge of the pathogen and methods of its control and explores potential avenues for future research focused on hypovirulence and biological control agents.

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.

Melon (Cucumis melo L.) production is often restricted by a plethora of pests and diseases, including powdery mildew and downy mildew caused respectively by the fungal species Podosphaera xanthii/Golovinomyces orontii and oomycete species Pseudoperonospora cubensis. Many efforts have been directed on identification of resistant sources by screening (wild) melon germplasm. In the current review, we summarized such efforts from various publications of the last 50 plus years. Resistance to powdery mildew has been identified in 239 melon accessions and downy mildew resistance in 452 accessions of both C. melo and the wild relative species C. figarei. Among the resistance sources, C. melo var. cantalupensis accessions PMR 45, PMR 5, PMR 6, and WMR 29 as well as C. melo var. momordica accessions PI 124111, PI 124112, and PI 414723 have been considered as the most valuable germplasm because multiple resistance genes have been identified from these accessions and are widely used in melon resistance breeding. Further genetic mapping in a number of resistant sources has enabled identification of 25 dominant genes, two recessive genes and seven QTLs conferring powdery mildew resistance, as well as eight dominant genes and 11 QTLs for downy mildew resistances. Based on the reported sequences of associated markers, we anchored physically (many of) these genes and QTLs to chromosomes of the melon cv. DHL92 genome. In addition to presenting a comprehensive overview on powdery mildew and downy mildew resistance in (wild) melon germplasm, we suggest strategies aiming at breeding melon with durable and broad-spectrum resistance to pathogens and pests.

In Colombia, floriculture is a very important section of the economy since it provides income to the country. Within this sector is the cultivation of roses (Rosa spp.), whose production and quality are affected by the presence of various pests and diseases. Among these pests are thrips Frankliniella occidentalis and mites Tetranychus urticae, and among the diseases are downy mildew Peronospora sparsa, powdery mildew Podosphaera pannosa and botrytis Botrytis cinerea. This problem generates large expenses in the purchase of agrochemical products for their control and management. This study analyzes the incidence of various pests and diseases in rose cultivation as a function of climatological variables (evaporation, temperature, relative humidity, and precipitation) in order to predict a future affectation. The analysis was carried out with R as programming language for the calculation of a multiple linear regression model. The results showed satisfactory prediction for the percentage incidence of each of the pests and diseases, since the difference between the predicted values and the values obtained by monitoring did not exceed 5% for the downy mildew, botrytis, mites, and thrips and 10% for the powdery mildew. The tool presented shows appropriate prediction for the possible behavior of the pests and diseases, and, thus, provides the opportunity to counteract their damage and estimate the investment required for their control. In this study, only the percentage incidence data of each of the pests and/or diseases was considered, as well as the value of the response variables in percentage incidence.

Downy mildew disease of sunflower, caused by the obligate biotrophic oomycete Plasmopara halstedii, can have significant economic impact on sunflower cultivation. Using high-throughput whole transcriptome sequencing, four developmental phases in 16 time-points of Pl. halstedii infecting Helianthus annuus were investigated. With the aim of identifying potential functional and regulatory motifs upstream of co-expressed genes, time-series derived gene expression profiles were clustered based on their time-course similarity, and their upstream regulatory gene sequences were analyzed here. Several conserved motifs were found upstream of co-expressed genes, which might be involved in binding specific transcription factors. Such motifs were also found associated with virulence related genes, and could be studied on a genetically tractable model to clarify, if these are involved in regulating different stages of pathogenesis. [ABSTRACT FROM AUTHOR]

Downy mildew caused by oomycete pathogen Plasmopara viticola is a devastating disease of grapevine. P. viticola secretes an array of RXLR effectors to enhance virulence. One of these effectors, PvRXLR131, has been reported to interact with grape (Vitis vinifera) BRI1 kinase inhibitor (VvBKI1). BKI1 is conserved in Nicotiana benthamiana and Arabidopsis thaliana. However, the role of VvBKI1 in plant immunity is unknown. Here, we found transient expression of VvBKI1 in grapevine and N. benthamiana increased its resistance to P. viticola and Phytophthora capsici, respectively. Furthermore, ectopic expression of VvBKI1 in Arabidopsis can increase its resistance to downy mildew caused by Hyaloperonospora arabidopsidis. Further experiments revealed that VvBKI1 interacts with a cytoplasmic ascorbate peroxidase, VvAPX1, an ROS-scavenging protein. Transient expression of VvAPX1 in grape and N. benthamiana promoted its resistance against P. viticola, and P. capsici. Moreover, VvAPX1 transgenic Arabidopsis is more resistant to H. arabidopsidis. Furthermore, both VvBKI1 and VvAPX1 transgenic Arabidopsis showed an elevated ascorbate peroxidase activity and enhanced disease resistance. In summary, our findings suggest a positive correlation between APX activity and resistance to oomycetes and that this regulatory network is conserved in V. vinifera, N. benthamiana, and A. thaliana. [ABSTRACT FROM AUTHOR]

The production of high-quality wines is strictly related to the correct management of the vineyard, which guarantees good yields and grapes with the right characteristics required for subsequent vinification. Winegrowers face a variety of challenges during the grapevine cultivation cycle: the most notorious are fungal and oomycete diseases such as downy mildew, powdery mildew, and gray mold. If not properly addressed, these diseases can irremediably compromise the harvest, with disastrous consequences for the production and wine economy. Conventional defense methods used in the past involved chemical pesticides. However, such approaches are in conflict with the growing attention to environmental sustainability and shifts from the uncontrolled use of chemicals to the use of integrated approaches for crop protection. Improvements in genetic knowledge and the availability of novel biotechnologies have created new scenarios for possibly producing grapes with a reduced, if not almost zero, impact. Here, the main approaches used to protect grapevines from fungal and oomycete diseases are reviewed, starting from conventional breeding, which allowed the establishment of new resistant varieties, followed by biotechnological methods, such as transgenesis, cisgenesis, intragenesis, and genome editing, and ending with more recent perspectives concerning the application of new products based on RNAi technology. Evidence of their effectiveness, as well as potential risks and limitations based on the current legislative situation, are critically discussed. [ABSTRACT FROM AUTHOR]

In disease assessment, the use of diagrammatic scales provides a standard reference point for comparison. There is still no precise and accurate scale for the evaluation of sporulation intensity of downy mildew in lettuce seedlings. The objective of this study was to propose a diagrammatic scale for the evaluation of downy mildew severity in lettuce seedlings. Thirty lettuce seedlings with different sporulation intensities were used to develop the proposed diagrammatic scale. Solaris lettuce cultivar was sown, and fifteen days after sowing, inoculations occurred using distilled water, the pathogen sporangia, and Tween 20. The monitoring of disease development was performed daily. When the first sporulation appeared on the cotyledonaryleaves, the proposed scale was verified to meet the minimum and maximum levels of disease severity. Two evaluators verified the accuracy, precision and performed the estimation of the sporulation and reproducibility using a scale. The images obtained are important in the standardization of a scale to identify resistant, tolerant and susceptible plants to downy mildew. Furthermore, it allows validating a diagrammatic scale of sporulation intensity of B. lactucae in lettuce seedlings. Thus, it is the diagrammatic scale developed in the work will guide future research to accelerate the detection of mildew severity in lettuce seedlings. [ABSTRACT FROM AUTHOR]

Background: Oxathiapiprolin is a novel fungicide and the first of the piperidinyl‐thiazole‐isoxazoline class to be discovered. This fungicide has been reported to have high activity against Plasmopara viticola, the grapevine downy mildew agent, and other plant‐pathogenic oomycetes. In this study, the baseline sensitivity of Italian P. viticola populations towards oxathiapiprolin was established on 29 samples collected in 10 different viticultural areas. Two insensitive strains were characterized for their mechanism of resistance. Results: Oxathiapiprolin exhibited substantial inhibitory activity against 27 of the 29 populations tested, with EC50 values ranging from a minimum of under 4 × 10−5 mg L−1 to over 4 × 10−1 mg L−1, with an average value of 3.2 × 10−2 mg L−1. Two stable suspected oxathiapiprolin‐resistant mutants were isolated from population exhibiting reduced sensitivity, and sequenced for the oxathiapiprolin target gene PvORP1. The comparison with wild‐type isolates revealed that the resistant isolates possessed a heterozygous mutation causing the amino acid substitution N837I, recently reported in the literature. Conclusion: The results obtained indicate a risk for Italian P. viticola populations to develop resistance to oxathiapiprolin in association with the N837I mutation at PvORP1. Anti‐resistance strategies should be carefully implemented and the sensitivity levels to this molecule should be monitored accurately in future to preserve its effectiveness. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Downy mildew, caused by Peronospora variabilis, is the most important quinoa disease worldwide. However, little is known about the resistance mechanisms acting against this disease. The study goals were to identify quinoa accessions showing resistance to P. variabilis under Spanish field conditions and to characterize the resistance mechanism involved. Towards these objectives, a total amount of 229 accessions of Chenopodium quinoa and one accession of each of the species Chenopodiun berlandieri subs. nutillae, Chenopodium ugandae, and Chenopodium opulifolium were screened for resistance to P. variabilis under field conditions in Córdoba, Spain, during two seasons. The response to P. variabilis in the accessions showed a continuous distribution ranging from complete resistance to high susceptibility. Fifteen resistant and one susceptible accessions were selected for further histological studies. Histological results showed that resistance to downy mildew in quinoa acts mainly at the stage of colony establishment. In resistant accessions, no colonies were formed or success in colony establishment was significantly reduced compared with the susceptible control. Hypersensitive response was associated with colony abortion in a number of the resistant accessions. This work is the first proof of hypersensitive reaction occurrence in quinoa as a response to P. variabilis. [ABSTRACT FROM AUTHOR]

Vitis vinifera L. is highly susceptible to the biotrophic pathogen Plasmopara viticola. To control the downy mildew disease, several phytochemicals are applied every season. Recent European Union requirements to reduce the use of chemicals in viticulture have made it crucial to use alternative and more sustainable approaches to control this disease. Our previous studies pinpoint the role of fatty acids and lipid signalling in the establishment of an incompatible interaction between grapevine and P. viticola. To further understand the mechanisms behind lipid involvement in an effective defence response we have analysed the expression of several genes related to lipid metabolism in three grapevine genotypes: Chardonnay (susceptible); Regent (tolerant), harbouring an Rpv3-1 resistance loci; and Sauvignac (resistant) that harbours a pyramid of Rpv12 and Rpv3-1 resistance loci. A highly aggressive P. viticola isolate was used (NW-10/16). Moreover, we have characterised the grapevine phospholipases C and D gene families and monitored fatty acid modulation during infection. Our results indicate that both susceptible and resistant grapevine hosts did not present wide fatty acid or gene expression modulation. The modulation of genes associated with lipid signalling and fatty acids seems to be specific to Regent, which raises the hypothesis of being specifically linked to the Rpv3 loci. In Sauvignac, the Rpv12 may be dominant concerning the defence response, and, thus, this genotype may present the activation of other pathways rather than lipid signalling. [ABSTRACT FROM AUTHOR]

Studies on wild and landrace hops from the Canadian Maritimes are scarce. This study was undertaken to broaden the genetic base of hops and to assess the reaction of the generated variants to downy mildew (DM) disease. A landrace hop (PE Royalty (P-RL)) and a commercial cultivar (Alpharoma) were mutagenized using ethylmethane sulphonate (EMS), and single nucleotide polymorphism (SNP) variations were determined using an amplicon sequencing genetic diversity study. A subset of wild types and a subset of mutagenized hops were inoculated with DM spores and rated for disease symptoms in a controlled environment. The data showed large EMS-induced genetic diversity in the target genes along with natural variations in the wild types. A diversity in DM resistance within the studied collection was also observed. The study showed DM tolerance in some P-RL landrace seedlings, suggesting that these P-RL landraces must have acquired and developed adaptation mechanisms to co-evolve with DM disease in the environment. Further, EMS-induced mutagenesis increased allelic variations that contributed to increased DM resistance in some seedlings. The data recommend the use of true hop seeds for increased genetic variability in breeding programs. [ABSTRACT FROM AUTHOR]

Downy mildew is a serious threat to corn (maize) production in the tropics and subtropics. Corn is native to Central America, and was introduced into South-East Asia by the Spanish colonisers in the 1700s. Corn is evolutionarily naïve to downy mildews of the genus Peronosclerospora. Consequently, corn monocultures are particularly susceptible to a variety of Peronosclerospora species, which spread to the crop from local grasses. Globally, corn is one of the most important crops for both humans and livestock. Several downy mildews of corn have been identified as potential threats to global food security, and trade with corn seeds is strictly regulated to avoid spreading the pathogens. Despite their importance, little is known about the biodiversity of graminicolous downy mildews, because their identification has often relied on variable morphological features, such as conidial dimensions. DNA barcodes for most species have become available only recently. During surveys for downy mildews on corn in Indonesia, a previously unrecognised species of Peronosclerospora was found and investigated using a combination of morphological characters and molecular phylogenetic analyses. The new species, introduced here as Peronosclerospora neglecta, is widely distributed in South-East Asia from Thailand to eastern Indonesia. The impact of this downy mildew can be severe, with complete crop losses in heavily affected fields. Given the aggressiveness of the species, close surveillance is warranted to restrict its further spread. [ABSTRACT FROM AUTHOR]

The Plasmopara viticola pathogen causes one of the most severe grapevine diseases, namely downy mildew. The response to P. viticola involves both visible symptoms and intricate metabolomic alterations, particularly in relation to volatile organic compounds, and depends on the degree of resistance of a particular variety. There are numerous native grapevine varieties in Croatia, and they vary in susceptibility to this oomycete. As previously reported, in vitro leaf disc bioassay and polyphenolic compound analysis are complementary methods that can be used to separate native varieties into various resistance classes. This research used the Solid Phase Microextraction-Arrow Gas Chromatography-Mass Spectrometry method to identify the early alterations in the VOCs in the leaves after P. viticola inoculation. Based on the absolute peak area of sesquiterpenes, some discrepancies between the sampling terms were noticed. The presence of certain chemical compounds such as humulene, ylangene, and α-farnesene helped distinguish the non-inoculated and inoculated samples. Although specific VOC responses to P. viticola infection of native varieties from various resistance classes could not be identified, the response of less susceptible native varieties and resistant controls was associated with an increase in the absolute peak area of several compounds, including geranylacetone, ß-ocimene, and (E)-2-hexen-1-ol. [ABSTRACT FROM AUTHOR]

Downy and powdery mildews are major grapevine diseases. In organic viticulture, a few fungicides with protectant activities (copper and sulphur in particular) can be used, and their preventative application frequently leads to unneeded spraying. The adoption of an epidemiological disease forecasting model could optimise the timing of treatments and achieve a good level of disease protection. In this study, the effectiveness of the EPI (Etat Potentiel d'Infection) model in predicting infection risk for downy and powdery mildews was evaluated in nine organic vineyards located in Panzano in Chianti (FI), over a 2-year period (2020–2021). The reliability of the EPI model was investigated by comparing the disease intensities, the number of fungicide sprayings, the quantities of the fungicides (kg/ha), and the costs of the treatment achieved, with or without the use of the model, in a vineyard. The results obtained over two seasons indicated that, in most cases, the use of the EPI model accurately signalled the infection risk and allowed for a reduction in the frequency and cost of spraying, particularly for powdery mildew control (−40% sprayings, −20% costs compared to the farmer's schedule), without compromising crop protection. The use of the EPI model can, therefore, contribute to more-sustainable disease management in organic viticulture. [ABSTRACT FROM AUTHOR]

The aim of this study was to contribute to the reduction of synthetic chemical fungicide application in viticulture by using cyclo(- l -Leu- l -Phe) (cLF) produced by Bacillus subtilis KS1, a candidate for biological control agent. cLF is a diketopiperazine and belongs to the family of 2,5-diketopiperazines. KS1 secreted micromolar levels of cLF into culture medium. Micromolar concentrations of cLF structure-dependently decreased by ∼90% both disease severity and lesion density of downy mildew in grapevine cultivated in a growth chamber. Microscopic observation demonstrated that cLF inhibited Plasmopara viticola haustorium formation by 80% but not zoospore germination on leas disks. Interestingly, millimolar concentrations of cLF induced plant defense response, such as expression of genes encoding chitinase and β-1,3-glucanase, in grapevine leaves through the salicylic acid and jasmonate signaling pathways. We demonstrated that cLF was a weapon against P. viticola infection. Further evaluation of cLF in field trials is required to uncover its inherent characteristics. [ABSTRACT FROM AUTHOR]

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The sunflower inbred line 33G was used as the experimental material, which was planted in the downy mildew disease nursery and the normal field, respectively, to examine changes in metabolites differences in metabolic pathways, and the mechanism of regulation of metabolic pathways in the process of sunflower susceptible to downy mildew. At the seedling stage, six biological replicates were collected from the leaves of diseased plants in the disease nursery and non-diseased plants in the normal field, respectively (S33G in the disease nursery and R33G in the normal field). The alterations in metabolites and metabolic pathways in susceptible and normal plants were studied by using LC/MS technology. The results demonstrate that in the S33G-R33G comparison group, 679 differentially expressed metabolites are screened, with 294 up-regulated metabolites and 385 down-regulated metabolites, and the differential metabolites are enriched to 58 metabolic pathways. Alkaloids, fatty acids, flavonoids, terpenoids, and polyketones are the most up-regulated differential metabolites, while lipids and lipid molecules, organic oxygen compounds, organic acids and derivatives, and other compounds are the most down-regulated differential metabolites. By comparison, it is discovered that arachidonic acid metabolism, diterpene biosynthesis, purine metabolism, oxidative phosphorylation, α-linolenic acid metabolism, citrate cycle (TCA cycle), nicotinate and nicotinamide metabolic pathways are considerably activated. [ABSTRACT FROM AUTHOR]

Environmental and economic costs demand a rapid transition to more sustainable farming systems, which are still heavily dependent on chemicals for crop protection. Despite their widespread application, powdery mildew (PM) and downy mildew (DM) continue to generate serious economic penalties for grape and wine production. To reduce these losses and minimize environmental impacts, it is important to predict infections with high confidence and accuracy, allowing timely and efficient intervention. This review provides an appraisal of the predictive tools for PM and DM in a vineyard, a specialized farming system characterized by high crop protection cost and increasing adoption of precision agriculture techniques. Different methodological approaches, from traditional mechanistic or statistic models to machine and deep learning, are outlined with their main features, potential, and constraints. Our analysis indicated that strategies are being continuously developed to achieve the required goals of ease of monitoring and timely prediction of diseases. We also discuss that scientific and technological advances (e.g., in weather data, omics, digital solutions, sensing devices, data science) still need to be fully harnessed, not only for modelling plant–pathogen interaction but also to develop novel, integrated, and robust predictive systems and related applied technologies. We conclude by identifying key challenges and perspectives for predictive modelling of phytopathogenic disease in vineyards. [ABSTRACT FROM AUTHOR]

Resistance of grapevine against powdery mildew (Erysiphe necator) and downy mildew (Plasmopara viticola) increases during ontogenetic development of leaves and berries. The aim of this study was to determine whether the use of fungicides against both pathogens could be reduced during the last treatment before harvest (LTBH) by treating only the susceptible leaves of the vines in the upper half of the canopy. For this purpose, field trials were carried out under experimental or practical conditions in vineyards in southern Germany in eight different years. All plants were sprayed after a standard regimen until LTBH, performed at BBCH 77–79. LTBH was either performed on the whole canopy or limited to the upper half of the canopy excluding the fruit zone. For both pathogens, no differences were observed between the two treatments with regard to the disease severity on the grape clusters. Only in one out of eight years, an increased fruit disease incidence could be observed. As far as the disease severity of leaves is concerned, no differences were observed for downy mildew, and in the case of powdery mildew, significantly higher infestation was observed only in two out of eight years. Furthermore, the efficacy of different fungicides for LTBH was investigated in a 3-year experiment. Sole use of a copper fungicide for LTBH had no disadvantages against E. necator, compared to a treatment with synthetic fungicides. Taken together, LTBH at BBCH 77–79 can be limited to the upper canopy without risk to the health of the fruit. [ABSTRACT FROM AUTHOR]

The importance of long non-coding RNA in plants has been reported more frequently in recent years, but there has been few specific reports on lncRNAs in grape, especially in terms of disease resistance. We performed RNA-seq on grape leaves of two species (Vitis piasezkii accession Liuba-8, Vitis vinifera cultivar Pinot Noir) sampled at six time points after inoculation, and 4011 possible lncRNAs were identified. The characteristics of grape lncRNAs were analyzed, and it was found that lncRNAs showed relatively consistent characteristics with the reported lncRNAs in model plants. 3,643 lncRNAs were predicted that have cis-regulatory effects on 6,622 protein-coding genes and 91 DElncRNAs were revealed to be coexpressed with its trans-regulated coding genes. One hundred and seventeen grape microRNAs were predicted to potentially target 184 lncRNAs and six lncRNAs were predicted to be endogenous targeting mimics of 15 microRNAs, among which some miRNAs have been reported in grape disease resistance. At six time points, LncRNAs showed different expression levels and different expression patterns in two species, suggesting that lncRNAs may have a certain regulatory effect on resistance to downy mildew in grape. Finally, a lncRNA MSTRG.12742.1 which may play a positive role in grape downy mildew resistance was verified by transient transformation. Its potential target gene, VIT_204s0008g02671.1, encodes cryptochrome DASH which may regulate stomatal opening and closing of plant leaves. In this study, we provided the systematic identification of lncRNAs in the course of downy mildew of grape, laying a foundation for further studies on downy mildew and lncRNAs of grape in the future.

Background: Downy mildew of foxtail millet, which is caused by the biotrophic oomycete Sclerospora graminicola (Sacc.) Schroeter, is one of the most disruptive diseases. The foxtail millet-S. graminicola interaction is largely unexplored. Transcriptome sequencing technology can help to reveal the interaction mechanism between foxtail millet and its pathogens. Results: Transmission electron microscopy observations of leaves infected with S. graminicola showed that the structures of organelles in the host cells gradually became deformed and damaged, or even disappeared from the 3- to 7-leaf stages. However, organelles in the leaves of resistant variety were rarely damaged. Moreover, the activities of seven cell wall degrading enzymes in resistant and susceptible varieties were also quite different after pathogen induction and most of enzymes activities were significantly higher in the susceptible variety JG21 than in the resistant variety G1 at all stages. Subsequently, we compared the transcriptional profiles between the G1 and JG21 in response to S. graminicola infection at 3-, 5-, and 7-leaf stages using RNA-Seq technology. A total of 473 and 1433 differentially expressed genes (DEGs) were identified in the resistant and susceptible varieties, respectively. The pathway analysis of the DEGs showed that the highly enriched categories were related to glutathione metabolism, plant hormone signalling, phenylalanine metabolism, and cutin, suberin and wax biosynthesis. Some defence-related genes were also revealed in the DEGs, including leucine-rich protein kinase, Ser/Thr protein kinase, peroxidase, cell wall degrading enzymes, laccases and auxin response genes. Our results also confirmed the linkage of transcriptomic data with qRT-PCR data. In particular, LRR protein kinase encoded by Seita.8G131800, Ser/Thr protein kinase encoded by Seita.2G024900 and Seita. 2G024800, which have played an essential resistant role during the infection by S. graminicola. Conclusions: Transcriptome sequencing revealed that host resistance to S. graminicola was likely due to the activation of defence-related genes, such as leucine-rich protein kinase and Ser/Thr protein kinase. Our study identified pathways and genes that contribute to the understanding of the interaction between foxtail millet and S. graminicola at the transcriptomic level. The results will help us better understand the resistance mechanism of foxtail millet against S. graminicola. [ABSTRACT FROM AUTHOR]

Grapevine, a crop of global economic importance, is annually affected by diseases that can compromise the quality and quantity of the harvest, producing large economic losses. Downy mildew caused by Plasmopara viticola (Berk. & M.A. Curtis) Berl. & de Toni is one of the most important diseases in the vineyard. To fight this pathogen, winegrowers often rely on conventional chemical fungicides or copper-based formulations, whose use is determined to be reduced by the European Commission due to their environmental consequences. Hence, alternative plant protection products (PPP) in grapevine must be considered and studied. In this context, we selected several alternative commercial products, based on basic substances (BS) or low-risk active substances (LRAS), to evaluate their suitability to deal with P. viticola. We measured the preventive activity of the products, both in vitro and in planta, as well as their toxicity against the sporangia and zoospores of the pathogen. Results showed that four commercial products were effective against the pathogen directly and preventively, being composed of approved basic substances, more concretely, chitosan, Equisetum arvense, lecithins, and Salix cortex. Among those, the products composed of lecithins and Salix cortex were the most toxic and active preventively. Therefore, these basic substances should be promoted in the vineyard as an alternative to conventional treatments in order to transition to a more sustainable viticulture. [ABSTRACT FROM AUTHOR]

In recent years, Septoria leaf spot has taken a strong place in the list of economically important diseases of sunflower. It may be a favorable factor for the development of other diseases on sunflower plants too. The aim of the research was to evaluate the frequency and degree of infection of sunflower plants with Septoria helianthi as well as possibility of simultaneous infection with this pathogen and other fungi which cause foliar spots, such as downy mildew, Alternaria leaf spot and Phoma black stem under conditions of stationary infectious nursery. The year 2021 turned out to be extremely favorable for the development of fungal leaf spots on sunflower. Assessment of fungal diseases of sunflower plants was performed in F2 families obtained after crossing ZL22A, ZL58A, ZL70A, ZL78A, and ZL169A lines of Zaporozhye breeding (Ukraine) with HAR7 line (originating from the USA). Each F2 family (sample) was obtained from self-pollination of one F1 plant with varying severity of Septoria disease. It was found that in the conditions of 2021, sunflower was quite affected by Septoria disease. The percentage of injured plants in F2 samples ranged from 41.0 to 100.0%. The severity of disease was different. Less resistant genotypes included plants with lesions on sunflower leaves of lower, middle, and upper tiers in approximately equal numbers, while more resistant genotypes had almost no plants with injured leaves of upper tiers. It was established that the development of Phoma disease occurred both on plants with Septoria leaf spot and on healthy plants. On average, among the plants infected with Phoma macdonaldii, the proportion of plants jointly affected by Phoma and Septoria diseases was 2/3. However, the frequency of simultaneous infection of plants with S. helianthi and P. macdonaldii in genotypes with different resistance to Septoria leaf spot differed significantly and ranged from 80% in less resistant to 40% in more resistant accessions. Most plants (about 90%) infected with Plasmopara halstedii were simultaneously infected with S. helianthi. That is, both of these pathogens can simultaneously develop on the same plant and lead to a decline in its basic physiological functions. The rate of simultaneous damage of sunflower by Alternaria and Septoria was quite low compared to plant damage by Alternaria alone and was less than 30%. This may mean that the pathogen of Alternaria leaf spot avoids plants with existing S. helianthi fungus. [ABSTRACT FROM AUTHOR]

Downy mildew is a major threat to the economic value of spinach. The most effective approach to managing spinach downy mildew is breeding cultivars with resistance genes. The resistance allele RPF2 is effective against races 1–10 and 15 of Peronospora farinosa f. sp. Spinaciae (P. effusa) and is widely used as a resistance gene. However, the gene and the linked marker of RPF2 remain unclear, which limit its utilization. Herein, we located the RPF2 gene in a 0.61 Mb region using a BC1 population derived from Sp39 (rr) and Sp62 (RR) cultivars via kompetitive allele specific PCR (KASP) markers. Within this region, only one R gene, Spo12821, was identified based on annotation information. The amino acid sequence analysis showed that there were large differences in the length of the LRR domain between the parents. Additionally, a molecular marker, RPF2-IN12821, was developed based on the sequence variation in the Spo12821, and the evaluation in the BC1 population produced a 100% match with resistance/susceptibility. The finding of the study could be valuable for improving our understanding of the genetic basis of resistance against the downy mildew pathogen and breeding resistance lines in the future. [ABSTRACT FROM AUTHOR]

Lettuce cultivation occurs throughout the year in tropical countries such as Brazil. However, the most favorable time for its cultivation is also favorable to some diseases, mainly lettuce downy mildew (Bremia lactucae), limiting its commercial production. This study aimed to show the viability of silicon (Si) as an inducer of resistance to lettuce downy mildew through a biochemical approach focused on the antioxidant responses of plants. Seeds were first sterilized in a solution of sodium hypochlorite (5%), rinsed three times and pre-treated or not with Si. Seed primming with Si (calcium silicate—CaSiO3) was used for this experiment, where Si application was performed by soaking or not the seeds in a Si (CaSiO3) solution (100 μmol L−1) for one hour before germination. Three-day old germinated seedlings were then further inoculated with lettuce downy mildew (SPBl:01 race) by spraying an sporangia suspension (5 × 104 mL−1) until run-off. Treatments were formed as following: seed priming with bidistilled water and non-inoculated seedlings (Control), seed priming with bidistilled water and inoculated seedlings (Inoculated), and seed priming with Si and inoculated seedlings (Inoculated + Si). The experiment was carried out under a completely randomized design (three treatments and five replicates—consisting of 50 seedlings). Plant growth, photosynthetic pigments (total chlorophyll and carotenoids) contents were measured. MDA and H2O2 content were also quantified, as well as the activity of major antioxidant enzymes (SOD, APX, GPX and GR). Our results showed that Si reduced disease incidence, increased photosynthetic pigments contents, maintained seedling growth, reduced MDA and H2O2 contents and increased the activity of the antioxidant enzymes SOD, APX and GPX. Therefore, Si triggered seedlings resistance to lettuce downy mildew by inducing enzymatic antioxidant defense systems, mainly in the peroxidases group, such as APX and GPX. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agriculture & Nature / Kahramanmaraş Sütçü İmam Üniversitesi Tarım & Doğa Dergisi is the property of Kahramanmaras Sutcu Imam Universitesi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Spinach (Spinacia oleracea) is a popular leafy vegetable crop and commercial production is centered in California and Arizona in the US. The oomycete Peronospora effusa causes the most important disease in spinach, downy mildew. A total of nineteen races of P. effusa are known, with more than 15 documented in the last three decades, and the regular emergence of new races is continually overcoming the genetic resistance to the pathogen. This study aimed to finely map the downy mildew resistance locus RPF3 in spinach, identify single nucleotide polymorphism (SNP) markers associated with the resistance, refine the candidate genes responsible for the resistance, and evaluate the prediction performance using multiple machine learning genomic prediction (GP) methods. Segregating progeny population developed from a cross of resistant cultivar Whale and susceptible cultivar Viroflay to race 5 of P. effusa was inoculated under greenhouse conditions to determine downy mildew disease response across the panel. The progeny panel and the parents were resequenced at low coverage (1x) to identify genome wide SNP markers. Association analysis was performed using disease response phenotype data and SNP markers in TASSEL, GAPIT, and GENESIS programs and mapped the race 5 resistance loci (RPF3) to 1.25 and 2.73 Mb of Monoe-Viroflay chromosome 3 with the associated SNP in the 1.25 Mb region was 0.9 Kb from the NBS-LRR gene SOV3g001250. The RPF3 locus in the 1.22-1.23 Mb region of Sp75 chromosome 3 is 2.41-3.65 Kb from the gene Spo12821 annotated as NBS-LRR disease resistance protein. This study extended our understanding of the genetic basis of downy mildew resistance in spinach cultivar Whale and mapped the RPF3 resistance loci close to the NBSLRR gene providing a target to pursue functional validation. Three SNP markers efficiently selected resistance based on multiple genomic selection (GS) models. The results from this study have added new genomic resources, generated an informed basis of the RPF3 locus resistant to spinach downy mildew pathogen, and developed markers and prediction methods to select resistant lines. [ABSTRACT FROM AUTHOR]

Yield losses in sunflower crops caused by Plasmopara halstedii can be up to 100%, depending on the cultivar susceptibility, environmental conditions, and virulence of the pathogen population. The aim of this study was to investigate the genetic and phenotypic structure of a sunflower downy mildew agent at the field scale. The genetic diversity of 250 P. halstedii isolates collected from one field in southern France was assessed using single-nucleotide polymorphisms (SNPs) and single sequence repeats (SSR). A total of 109 multilocus genotypes (MLG) were identified among the 250 isolates collected in the field. Four genotypes were repeated more than 20 times and spatially spread over the field. Estimates of genetic relationships among P. halstedii isolates using principal component analysis and a Bayesian clustering approach demonstrated that the isolates are grouped into two main genetic clusters. A high level of genetic differentiation among clusters was detected (FST = 0.35), indicating overall limited exchange between them, but our results also suggest that recombination between individuals of these groups is not rare. Genetic clusters were highly related to pathotypes, as previously described for this pathogen species. Eight different races were identified (100, 300, 304, 307, 703, 704, 707, and 714), with race 304 being predominant and present at most of the sites. The co-existence of multiple races at the field level is a new finding that could have important implications for the management of sunflower downy mildew. These data provide the first population-wide picture of the genetic structure of P. halstedii at a fine spatial scale. [ABSTRACT FROM AUTHOR]

Onion downy mildew caused by Peronospora destructor has been widespread in Japan since 2016. Soil disinfection and use of fungicides have been implemented as control measures against oospores in the soil, which are the primary source of infection. Measurements of oospore density are needed to clarify the risk of disease development and inform disease management. In this study, an experimental system capable of detecting P. destructor DNA from field samples was developed. A TaqMan probe‐type primer was used to target the coxII (cytochrome c oxidase subunit II) region of the mitochondrial genome of P. destructor and no false positives were observed. Using this method, the detection limit was equivalent to 5 oospores of P. destructor/g soil in grey lowland soil and andosol. The correlation coefficient between oospore density and the primary infection rate was investigated by testing soil samples from 115 fields. Although no correlations between oospore density and the primary infection were observed in pesticide‐treated fields, significant correlations were observed in untreated fields. Continuous cropping of onions increased the oospore density. The correlation between primary and secondary infection was relatively weak, and the negative predictive value of primary infection was relatively high (89.0). These results suggest that the disease‐risk potential of onion downy mildew is very high, and thus it is necessary to set a low pathogen detection threshold. The system presented here provides a highly sensitive method for supporting decision‐making aimed at disease control. [ABSTRACT FROM AUTHOR]

The susceptibility of commonly grown grapevine cultivars in the province of Quebec to Plasmopara viticola (Berk. & M.A. Curtis) Berl. & De Toni clades riparia and aestivalis was compared. The relationship between anatomic (density and size of stomata and type of leaf hairs) and genetic composition (percentages of Vitis vinifera L., Vitis riparia Michx. and Vitis aestivalis Michx.) factors of the grapevine cultivars and their susceptibility to the two clades was investigated. The grapevine cultivars were classified according to their susceptibility to each clade. The aggressiveness of the clade riparia was positively correlated with stomata size and negatively correlated with type of leaf hairs. However, the aggressiveness of clade aestivalis was positively correlated with stomata size and density, estimated percentage of V. vinifera ancestry, and the published downy mildew susceptibility of grapevine cultivars; and negatively correlated with estimated percentage of V. riparia ancestry. Furthermore, the grapevine cultivar classification showed that, for P. viticola clade riparia, 44.4%, 44.4%, and 11.1% of the grapevine cultivars were classified as minimally susceptible, moderately susceptible, and highly susceptible, respectively. Alternatively, for P. viticola clade aestivalis, 11.1%, 22.2%, and 66.7% of the grapevine cultivars were classified as minimally susceptible, moderately susceptible, and highly susceptible, respectively. Although some grapevine cultivars fell in the same susceptibility groups for both clades, 78% of grapevine cultivars were classified in different susceptibility groups. The findings of this study provide new information on grapevine and P. viticola interactions, and highlight the importance of knowing which clade of P. viticola is present so that downy mildew control measures can be adapted accordingly. La sensibilité des cépages de vigne couramment cultivés au Québec à Plasmopara viticola (Berk. & M.A. Curtis) Berl. & De Toni clades riparia et aestivalis a été déterminée sur disques de feuilles et sur feuilles entières sur plants. Par la suite, la relation entre les caractéristiques anatomiques (taille et densité des stomates, et poils foliaires) et génétiques (pourcentages de l'héritage génétique de Vitis vinifera L., Vitis riparia Michx. et Vitis aestivalis Michx.) des cépages et leur sensibilité aux deux clades a été étudiées, et les cépages classés en fonction de leur sensibilité à chacun des clades. L'agressivité du clade riparia était positivement corrélée à la taille des stomates et négativement corrélée aux poils foliaires. Tandis que l'agressivité du clade aestivalis était positivement corrélée à la taille et la densité des stomates, au pourcentage estimé de l'ascendance de V. vinifera, et aux données publiées de sensibilité des cépages, et était négativement corrélée au pourcentage estimé de l'ascendance de V. riparia. Par ailleurs, les résultats issus de la classification des cépages ont montré pour ce qui est du clade riparia que 44,4%, 44,4% et 11,1% des cépages étaient respectivement classés peu sensibles, moyennement sensibles et très sensibles. Cependant, pour ce qui est du clade aestivalis, 11,1%, 22,2% et 66,7% des cépages étaient respectivement classés peu sensibles, moyennement sensibles et très sensibles. Bien que certains cépages aient été classés dans les mêmes groupes de sensibilité aux deux clades, 78% des cépages étaient classés dans des groupes de sensibilité différents. Les résultats issus de cette étude apportent des informations essentielles pour une meilleure compréhension de l'interaction entre la vigne et P. viticola, et pour une gestion raisonnée et durable du mildiou de la vigne. [ABSTRACT FROM AUTHOR]

Copyright of Revista Caatinga is the property of Revista Caatinga and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plant resistance inducers (PRIs) are promising alternatives to chemical fungicides. Their effectiveness against grapevine downy mildew (DM) has been demonstrated for leaves, yet research on berry clusters is limited. We investigated the efficacy of six PRIs on clusters of cv. Barbera and Merlot from the end of flowering (growth stage GS 69) to fruit setting (GS 71) and inoculated with a sporangial suspension of Plasmopara viticola (Pv) at 1, 3, 6, 12, and 19 days after treatment (DAT). Cerevisane (CER) and Pythium oligandrum (PYT) did not reduce DM severity compared to the nontreated control (NT). Fosetyl-Al (FOS) reduced DM severity at 1-6 DAT, with >50% reduction compared to NT. Laminarin (LAM) was effective at 6, 12, and 19 DAT, with 42.7%-to 50.0% efficacy compared to NT, while cos-oga (COS) and K-phosphonate (PHO) were effective at 12 and 19 DAT (60% efficacy). PRIs were also applied to clusters at initial flowering (GS 60), GS 69-71, and pea-sized berries (GS 75), which were then inoculated with Pv at 7 DAT. At GS 60, treatments with LAM and PHO reduced disease severity compared to NT by 77.5% and 83.6%, respectively. At GS 69-71, LAM, PHO, and FOS caused 54.7%-75.7% disease reduction. At GS 75, all PRIs exhibited a disease reduction > 75%. The efficacy of PRIs increased as the cluster developmental stage advanced, indicating an interaction with the ontogenic resistance of berries. Our results are relevant for the practical use of PRIs in protecting grapevine clusters from DM.

Pseudoperonospora cubensis (downy mildew) is highly virulent to various Cucurbitaceae crops, including cucumber (Cucumis sativus). We tested chlorine dioxide application in a plastic greenhouse for environmentfriendly control of downy mildew disease. Spraying diluted chlorine dioxide suppressed downy mildew disease with 41.2% control efficacy. Thermal fogging with chlorine dioxide had a high control efficacy of 80.9%, confirming that this approach is useful for environment-friendly downy mildew control. Using thermal fogging to control diseases that are greatly affected by humidity, such as downy mildew, may be more effective compared with conventional dilution spray control methods.

Abstract Background The high susceptibility of European grapevine cultivars (Vitis vinifera) to downy mildew (Plasmopara viticola) leads to the intensive use of fungicides in viticulture. To reduce this input, breeding programs have introgressed resistance loci from wild Vitis species into V. vinifera, resulting in new fungus-resistant grapevine cultivars (FRC). However, little is known about how these different resistance loci confer resistance and what the potential reduction in fungicide applications are likely to be if these FRCs are deployed. To ensure a durable and sustainable resistance management and breeding, detailed knowledge about the different defense mechanisms mediated by the respective Rpv (Resistance to P. viticola) resistance loci is essential. Results A comparison of the resistance mechanisms mediated by the Rpv3–1, Rpv10 and/or Rpv12-loci revealed an early onset of programmed cell death (PCD) at 8 hours post infection (hpi) in Rpv12-cultivars and 12 hpi in Rpv10-cultivars, whereas cell death was delayed in Rpv3-cultivars and was not observed until 28 hpi. These temporal differences correlated with an increase in the trans-resveratrol level and the formation of hydrogen peroxide shortly before onset of PCD. The differences in timing of onset of Rpv-loci specific defense reactions following downy mildew infection could be responsible for the observed differences in hyphal growth, sporulation and cultivar-specific susceptibility to this pathogen in the vineyard. Hereby, Rpv3- and Rpv12/Rpv3-cultivars showed a potential for a significant reduction of fungicide applications, depending on the annual P. viticola infection pressure and the Rpv-loci. Furthermore, we report on the discovery of a new P. viticola isolate that is able to overcome both Rpv3- and Rpv12-mediated resistance. Conclusion This study reveals that differences in the timing of the defense reaction mediated by the Rpv3-, Rpv10- and Rpv12-loci, result in different degrees of natural resistance to downy mildew in field. Vineyard trials demonstrate that Rpv12/Rpv3- and Rpv3-cultivars are a powerful tool to reduce the dependence of grape production on fungicide applications. Furthermore, this study indicates the importance of sustainable breeding and plant protection strategies based on resistant grapevine cultivars to reduce the risk of new P. viticola isolates that are able to overcome the respective resistance mechanism.

There is growing interest in the application of ultraviolet (UV-C) energy to control crop pathogens. In the present study, the efficacies of UV-C treatments for controlling cucumber downy mildew (Pseudoperonospora cubensis) were investigated on a commercial farm in eastern Massachusetts, USA. Controlled doses of UV-C, delivered by a tractor-mounted array of sources, between 120 and 480 J·m-2 were applied and compared to conventional fungicide treatments as well as to untreated controls, for each of two consecutive years (2020 and 2021). Visual assessments of foliar disease severity in the trial plots were made several times from planting through the end of productive life. In contrast to the successful control of powdery mildew, the UV-C treatments for controlling cucumber downy mildew were not as successful as conventional fungicides. None of the UV-C treatments affected the overall progression rate of downy mildew once the disease became apparent, although disease onset was delayed slightly compared to untreated controls. This delay may have been due to UV-C induced resistance to infection by the host. Unlike powdery mildews, downy mildew spores from P. cubensis are darkly pigmented, possibly decreasing the efficacy of the UV-C treatments for controlling the disease. DM spores may also be only susceptible to UV exposure prior to encysting in the leaves of the host, thereby perhaps limiting the window of opportunity when UV-C treatments can be effective. Although not the primary focus of this study, the use of reflective mulch appeared to delay disease onset relative to black mulch in fields with significant sunlight exposure, perhaps due to lowering plant stress by maintaining a lower soil temperature.

Spinach (Spinacia oleracea) is a popular leafy vegetable crop and commercial production is centered in California and Arizona in the US. The oomycete Peronospora effusa causes the most important disease in spinach, downy mildew. A total of nineteen races of P. effusa are known, with more than 15 documented in the last three decades, and the regular emergence of new races is continually overcoming the genetic resistance to the pathogen. This study aimed to finely map the downy mildew resistance locus RPF3 in spinach, identify single nucleotide polymorphism (SNP) markers associated with the resistance, refine the candidate genes responsible for the resistance, and evaluate the prediction performance using multiple machine learning genomic prediction (GP) methods. Segregating progeny population developed from a cross of resistant cultivar Whale and susceptible cultivar Viroflay to race 5 of P. effusa was inoculated under greenhouse conditions to determine downy mildew disease response across the panel. The progeny panel and the parents were resequenced at low coverage (1x) to identify genome wide SNP markers. Association analysis was performed using disease response phenotype data and SNP markers in TASSEL, GAPIT, and GENESIS programs and mapped the race 5 resistance loci (RPF3) to 1.25 and 2.73 Mb of Monoe-Viroflay chromosome 3 with the associated SNP in the 1.25 Mb region was 0.9 Kb from the NBS-LRR gene SOV3g001250. The RPF3 locus in the 1.22-1.23 Mb region of Sp75 chromosome 3 is 2.41-3.65 Kb from the gene Spo12821 annotated as NBS-LRR disease resistance protein. This study extended our understanding of the genetic basis of downy mildew resistance in spinach cultivar Whale and mapped the RPF3 resistance loci close to the NBS-LRR gene providing a target to pursue functional validation. Three SNP markers efficiently selected resistance based on multiple genomic selection (GS) models. The results from this study have added new genomic resources, generated an informed basis of the RPF3 locus resistant to spinach downy mildew pathogen, and developed markers and prediction methods to select resistant lines.

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.

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.

Downy mildew is one of the most destructive diseases affecting grapevines (Vitis vinifera L.). Caused by the oomycete Plasmopara viticola (Berk. and Curt.) Berl. and de Toni, it can appear anywhere where vines are cultivated. It is habitually controlled by the application of phytosanitary agents (copper-based or systemic) at different stages of the vine growth cycle. This, however, is costly, can lead to reduced yields, has a considerable environmental impact, and its overuse close to harvest can cause fermentation problems. All grapevines are susceptible to this disease, although the degree of susceptibility differs between varieties. Market demands and European legislation on viticulture and the use of phytosanitary agents (art. 14 of Directive 128/2009/EC) now make it important to know the sensitivity of all available varieties, including minority varieties. Such knowledge allows for a more appropriate use of phytosanitary agents, fosters the commercial use of these varieties and thus increases the offer of wines associated with different terroirs, and helps identify material for use in crop improvement programmes via crossing or genetic transformation, etc. Over 2020–2021, the susceptibility to P. viticola of 63 minority vine varieties from different regions of Spain was examined in the laboratory using the leaf disc technique. Some 87% of these varieties were highly susceptible and 11% moderately susceptible; just 2% showed low susceptibility. The least susceptible of all was the variety Morate (Madrid, IMIDRA). Those showing intermediate susceptibility included the varieties Sanguina (Castilla la Mancha, IVICAM), Planta Mula (Comunidad Valenciana, ITVE), Rayada Melonera (Madrid, IMIDRA), Zamarrica (Galicia, EVEGA), Cariñena Roja (Cataluña, INCAVI), Mandrègue (Aragón, DGA) and Bastardo Blanco (Extremadura, CICYTEX). The highly susceptible varieties could be differentiated into three subgroups depending on sporulation severity and density.

Plant disease evaluation is crucial to pathogen management and plant breeding. Human field scouting has been widely used to monitor disease progress and provide qualitative and quantitative evaluation, which is costly, laborious, subjective, and often imprecise. To improve disease evaluation accuracy, throughput, and objectiveness, an image-based approach with a deep learning-based analysis pipeline was developed to calculate infection severity of grape foliar diseases. The image-based approach used a ground imaging system for field data acquisition, consisting of a custom stereo camera with strobe light for consistent illumination and real time kinematic (RTK) GPS for accurate localization. The deep learning-based pipeline used the hierarchical multiscale attention semantic segmentation (HMASS) model for disease infection segmentation, color filtering for grapevine canopy segmentation, and depth and location information for effective region masking. The resultant infection, canopy, and effective region masks were used to calculate the severity rate of disease infections in an image sequence collected in a given unit (e.g., grapevine panel). Fungicide trials for grape downy mildew (DM) and powdery mildew (PM) were used as case studies to evaluate the developed approach and pipeline. Experimental results showed that the HMASS model achieved acceptable to good segmentation accuracy of DM (mIoU > 0.84) and PM (mIoU > 0.74) infections in testing images, demonstrating the model capability for symptomatic disease segmentation. With the consistent image quality and multimodal metadata provided by the imaging system, the color filter and overlapping region removal could accurately and reliably segment grapevine canopies and identify repeatedly imaged regions between consecutive image frames, leading to critical information for infection severity calculation. Image-derived severity rates were highly correlated (r > 0.95) with human-assessed values, and had comparable statistical power in differentiating fungicide treatment efficacy in both case studies. Therefore, the developed approach and pipeline can be used as an effective and efficient tool to quantify the severity of foliar disease infections, enabling objective, high-throughput disease evaluation for fungicide trial evaluation, genetic mapping, and breeding programs. [ABSTRACT FROM AUTHOR]

Rust and downy mildew (DM) are two important sunflower diseases that lead to significant yield losses globally. The use of resistant hybrids to control rust and DM in sunflower has a long history. The rust resistance genes, R13a and R16, were previously mapped to a 3.4 Mb region at the lower end of sunflower chromosome 13, while the DM resistance gene, Pl33, was previously mapped to a 4.2 Mb region located at the upper end of chromosome 4. High-resolution fine mapping was conducted using whole genome sequencing of HA-R6 (R13a) and TX16R (R16 and Pl33) and large segregated populations. R13a and R16 were fine mapped to a 0.48 cM region in chromosome 13 corresponding to a 790 kb physical interval on the XRQr1.0 genome assembly. Four disease defense-related genes with nucleotide-binding leucine-rich repeat (NLR) motifs were found in this region from XRQr1.0 gene annotation as candidate genes for R13a and R16. Pl33 was fine mapped to a 0.04 cM region in chromosome 4 corresponding to a 63 kb physical interval. One NLR gene, HanXRQChr04g0095641, was predicted as the candidate gene for Pl33. The diagnostic SNP markers developed for each gene in the current study will facilitate marker-assisted selections of resistance genes in sunflower breeding programs. [ABSTRACT FROM AUTHOR]