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Oomycetes, a large group of fungus-like organisms, include some destructive plant pathogens causing enormous economic damage. Phylogenetically, oomycetes belong to the kingdom Straminipila and have diverse lifestyles, including saprotrophs and both general and specialized pathogens of various eukaryotic supergroups. A rapid increase in genomic studies and next-generation sequencing technologies have led to significant progress in understanding oomycete lifestyles. However, their genetics, including transcriptional regulation, have been studied to a much lesser extent. Here, we provide a cross-species analysis of oomycete promoter for providing a first step towards elucidating gene regulation networks related to pathogenicity and life cycle stages. The clustered DNA sequences of Plasmopara halstedii transcriptome time-series expression level dataset from a preliminary study have been used as a core reference for cross-species comparisons. Using a computational pipeline, 46 potential transcription factor binding site (TFBS) motifs in 25 clusters with functionally conserved downstream genes of downy mildew and two Phytophthora species, regardless of the gene expression levels of Phytophthora transcriptomes, were found. This can now be followed up by knock-out experiments in oomycete species amenable for genetic modification. [ABSTRACT FROM AUTHOR]

Cyclophilins (CYPs), a highly-conserved family of proteins, belong to a subgroup of immunophilins. Ubiquitous in eukaryotes and prokaryotes, CYPs have peptidyl-prolyl cis-trans isomerase (PPIase) activity and have been implicated as virulence factors in plant pathogenesis by oomycetes. We identified 16 CYP orthogroups from 21 diverse oomycetes. Each species was found to encode 15 to 35 CYP genes. Three of these orthogroups contained proteins with signal peptides at the N-terminal end, suggesting a role in secretion. Multidomain analysis revealed five conserved motifs of the CYP domain of oomycetes shared with other eukaryotic PPIases. Expression analysis of CYP proteins in different asexual life stages of the hemibiotrophic Phytophthora infestans and the biotrophic Plasmopara halstedii demonstrated distinct expression profiles between life stages. In addition to providing detailed comparative information on the CYPs in multiple oomycetes, this study identified candidate CYP effectors that could be the foundation for future studies of virulence.

There are approximately 700 obligate biotrophic species grouped into 20 genera (Oomycota, Peronosporaceae) that cause downy mildew diseases. In 2001, Dick hypothesized that diversification of downy mildew species was driven in part by host plant secondary metabolites. Dick further speculated that this was driven by the transition of host plants away from mycorrhizal associations or the evolution of C4 photosynthesis. Specifically, loss of mycorrhizal associations or the use of C4 photosynthesis would result in more free carbon that the plants could then use to produce more secondary metabolites. If true, then there should be more downy mildew species that infect hosts from plant lineages that lack mycorrhizal associations or use C4 photosynthesis. However, analysis of 677 downy mildew species for host plant mycorrhizal associations and host plant photosynthetic pathway type shows that this is not what occurred. Seventy percent of downy mildew species parasitize hosts that form mycorrhizal associations, and 94% of downy mildew species parasitize hosts that use C3 photosynthesis. From this, it is concluded that the diversification of downy mildew species was not driven by the loss of mycorrhizal associations or the evolution of C4 photosynthesis. However, 85% of downy mildew species that parasitize Poaceae (grasses) parasitize C4 hosts. Thus, it is possible that C4 photosynthesis plays a role in the diversification of these genera. [Figure: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2022.

Downy mildew caused by the oomycete Plasmopara halstedii (Farl.) Berl. et de Toni is one of the most harmful sunflower diseases. Among the various measures to control it, the most economical is the development of resistant genotypes. At present, Pl6, Pl8, and Plarg loci are promising for use in breeding, providing resistance to all known P. halstedii races. Microsatellite markers (SSR) help to control the transfer of genes that control resistance in breeding material. However, validation of the marker is needed to prove its reliability in gene detection. There was studied the polymorphism of 9 microsatellite loci in 196 sunflower lines with different resistance to downy mildew. The ORS328 microsatellite locus was chosen as a marker of the Pl6 gene. Amplified fragment with 271 bp allows identifying genotypes resistant to the race 330. The lines that are the sources of the Pl8 gene did not differ from the others in the allelic composition of the ORS781 locus. Among the analyzed breeding samples, no polymorphism was revealed at this locus. To identify the Plarg gene, SSR markers ORS662 and ORS509 were selected. The analysis of 12 samples of the F2 generation from RHA-419 × I3BC2 (VK585 × VK195) crossing at these loci showed that both markers are inherited codominantly. The studied DNA markers can be used in markerassisted selection (MAS) of sunflower for resistance to downy mildew pathogen. [ABSTRACT FROM AUTHOR]

Downy mildew of sunflower, caused by Plasmopara halstedii (Farl.) Berl. et de Toni, is a relevant disease of this crop. High virulent pathotypes have been identified in several countries, while there are few data on the spread of P. halstedii pathotypes in some important sunflower-growing areas of Europe. The goal of this study was to give up-to-date information on the pathotype structure of P. halstedii in Hungary and provide some actual data on the virulence phenotype of the pathogen for six European countries. Infected leaves of different sunflower hybrids and volunteers were collected in seven countries (Hungary, Bulgaria, Serbia, Turkey, Greece, Romania, and Italy) between 2012 and 2019. A universally accepted nomenclature was used with a standardized set of sunflower differential lines for pathotype characterization of isolates. The virulence pattern of the isolates was determined by a three-digit code (coded virulence formula, CVF). A total of 109 P. halstedii isolates were characterized. As a result of our survey, 18 new P. halstedii pathotypes were identified in Europe. Two out of the eighteen pathotypes were detected from the Asian part of Turkey. The detailed distribution of pathotypes in Hungary is also discussed. [ABSTRACT FROM AUTHOR]

Plant pathogenic oomycetes deliver a troop of effector proteins into the nucleus of host cells to manipulate plant cellular immunity and promote colonization. Recently, researchers have focused on identifying how effectors are transferred into the host cell nucleus, as well as the identity of the nuclear targets. In this study, we found that the RxLR effector PvAVH53 from the grapevine (Vitis vinifera) oomycete pathogen Plasmopara viticola physically interacts with grapevine nuclear import factor importin alphas (VvImpα and VvImpα4), localizes to the nucleus and triggers cell death when transiently expressed in tobacco (Nicotiana benthamiana) cells. Deletion of a nuclear localization signal (NLS) sequence from PvAVH53 or addition of a nuclear export signal (NES) sequence disrupted the nuclear localization of PvAVH53 and attenuated its ability to trigger cell death. Suppression of two tobacco importin-α genes, namely, NbImp-α1 and NbImp-α2, by virus-induced gene silencing (VIGS) also disrupted the nuclear localization and ability of PvAVH53 to induce cell death. Likewise, we transiently silenced the expression of VvImpα/α4 in grape through CRISPR/Cas13a, which has been reported to target RNA in vivo. Finally, we found that attenuating the expression of the Importin-αs genes resulted in increased susceptibility to the oomycete pathogen Phytophthora capsici in N. benthamiana and P. viticola in V. vinifera. Our results demonstrate that importin-αs are required for the nuclear localization and function of PvAVH53 and are essential for host innate immunity. The findings provide insight into the functions of importin-αs in grapevine against downy mildew. [ABSTRACT FROM AUTHOR]

Seed yield decrease at sunflower genotypes infected with pathogen Plasmopara halstedii because the plants remain small and the seeds are dry. In last years, sunflower downy mildew has developed new races and it is important to identifying which races is present. In year 2021, in Fundulea location we tested a differential set for sunflower downy mildew and identified 12 races of pathogen Plasmopara halstedii: 300, 304, 310, 314, 330, 334, 700, 703, 704, 710, 714, 731. New races present in Fundulea location, in year 2021 are 703, 704 and 731. [ABSTRACT FROM AUTHOR]

Plasmopara viticola is the causal agent of grapevine downy mildew (DM). DM resistant varieties deploy effector-triggered immunity (ETI) to inhibit pathogen growth, which is activated by major resistance loci, the most common of which are Rpv3 and Rpv12. We previously showed that a quick metabolome response lies behind the ETI conferred by Rpv3 TIR-NB-LRR genes. Here we used a grape variety operating Rpv12-mediated ETI, which is conferred by an independent locus containing CC-NB-LRR genes, to investigate the defence response using GC/MS, UPLC, UHPLC and RNA-Seq analyses. Eighty-eight metabolites showed significantly different concentration and 432 genes showed differential expression between inoculated resistant leaves and controls. Most metabolite changes in sugars, fatty acids and phenols were similar in timing and direction to those observed in Rpv3-mediated ETI but some of them were stronger or more persistent. Activators, elicitors and signal transducers for the formation of reactive oxygen species were early observed in samples undergoing Rpv12-mediated ETI and were paralleled and followed by the upregulation of genes belonging to ontology categories associated with salicylic acid signalling, signal transduction, WRKY transcription factors and synthesis of PR-1, PR-2, PR-5 pathogenesis-related proteins. [ABSTRACT FROM AUTHOR]

The obligatory biotrophic oomycetes Plasmopara viticola is the causal agent of downy mildew, a destructive disease of grapevine worldwide. So far, chemical fungicides are widely employed to limit this pathogen, but their adverse effects are stimulating the quest for environmentally friendly alternative approaches. Here, we report on the search for mycoviruses that might be later developed as biocontrol agents for this pathogen. Symptomatic leaves were collected from various regions in Spain and Italy and mycelia associated to leaf lesions was harvested. Total RNA extractions were depleted of rRNA and metatranscriptomes were generated using a high-throughput sequencing approach. The virome associated to leaf lesions was then characterized through a bioinformatic pipeline relying on blast searches against current viral databases. Here, we present an inventory of 283 new RNA viruses: 222 positive strand RNA viruses, 29 negative strand RNA viruses, 27 double-stranded RNA viruses and 5 ORFan virus RdRP segments, which could not be reliably assigned to any existing group in the Riboviria. In addition to ORFan viruses, we found other surprising new evolutionary trajectories in this wide inventory of viruses. The most represented viruses in our collection are those in phylum Lenarviricota , and, among them, a group of mycovirus segments distantly related to narnaviruses, but characterized by a polymerase palm domain lacking subdomain C, with the putative GDD catalytic triad. We also provided evidence of a strict association between two RNA segments that form a new mycovirus clade of positive strand RNA in the phylum Kitrinoviricota , order Martellivirales. In the phylum Negarnaviricota , we report for the first time in the order Mononegavirales a clade of viruses that is ambisense, a feature that so far was present only in the order Bunyavirales. Furthermore, in the same phylum we detected the widespread occurrence and abundant accumulation in our libraries of a distinct mycovirus clade distantly related to the Muvirales and Goujanvirales orders, which so far include only viruses infecting invertebrates. Possible new oomycetes-specific virus clades are also described in the phylum Duplornaviricota. These data greatly expand the evolutionary history of mycoviruses adding new layers of diversity to the realm Riboviria. [ABSTRACT FROM AUTHOR]

Downy mildew of sunflower caused by Plasmopara halstedii, is the most important disease of sunflower throughout the world including Turkey. Within the scope of the study, surveys were performed in Tekirdağ, Edirne, Kırklareli, Ankara, Bursa, Samsun, Tokat and Adana provinces where sunflower is widely grown in the period of 2009-2015. During the surveys, sixty-five P. halstedii isolates were obtained and purified. Using the race differentials set, nine races of the pathogen (100, 102, 110, 300, 500, 502, 510, 702 and 712) were determined. All races determined are first records for Turkey, whereas the races 102, 510 and 110 are the first record for the world. Almost 71% percent of the races were belonged to race 100. The reactions of 19 commercial sunflower cultivars against P. halstedii were determined by using isolates representing different races of downy mildew. None of the commercial sunflower cultivars showed resistance against all the races of P. halstedii at the same time. Among varieties tested LG5580 was found to be resistant to four races, whereas Sanay MR, Sanbro MR, LG540HO, and Sanbro varieties were found to be 3,3,2 and 1 races, respectively. [ABSTRACT FROM AUTHOR]

Summary: Over the last 40 years, new sunflower downy mildew isolates (Plasmopara halstedii) have overcome major gene resistances in sunflower, requiring the identification of additional and possibly more durable broad‐spectrum resistances. Here, 354 RXLR effectors defined in silico from our new genomic data were classified in a network of 40 connected components sharing conserved protein domains. Among 205 RXLR effector genes encoding conserved proteins in 17 P. halstedii pathotypes of varying virulence, we selected 30 effectors that were expressed during plant infection as potentially essential genes to target broad‐spectrum resistance in sunflower. The transient expression of the 30 core effectors in sunflower and in Nicotiana benthamiana leaves revealed a wide diversity of targeted subcellular compartments, including organelles not so far shown to be targeted by oomycete effectors such as chloroplasts and processing bodies. More than half of the 30 core effectors were able to suppress pattern‐triggered immunity in N. benthamiana, and five of these induced hypersensitive responses (HR) in sunflower broad‐spectrum resistant lines. HR triggered by PhRXLRC01 co‐segregated with Pl22 resistance in F3 populations and both traits localized in 1.7 Mb on chromosome 13 of the sunflower genome. Pl22 resistance was physically mapped on the sunflower genome recently sequenced, unlike all the other downy mildew resistances published so far. PhRXLRC01 and Pl22 are proposed as an avirulence/resistance gene couple not previously described in sunflower. Core effector recognition is a successful strategy to accelerate broad‐spectrum resistance gene identification in complex crop genomes such as sunflower. Significance Statement: Five RXLR‐type effectors of the sunflower downy mildew pathogen conserved in 17 pathotypes of varying virulence, triggered plant immunity in six broad‐spectrum resistant sunflower lines, including two unpublished resistances to all pathotypes. Effector recognition accelerated plant resistance gene identification and fine mapping in complex crop genomes such as sunflower, for which no resistance gene has so far been characterized. [ABSTRACT FROM AUTHOR]

Grey mould, powdery mildew, and downy mildew are the most frequent fungal diseases among vineyards worldwide. In the present study, we analysed the influence of the fungi causing these diseases (Botrytis, Erysiphe, and Plasmopara, respectively) on two viticulture areas from North-western (NW) Spain during three growth seasons (2016, 2017, and 2018). The obtained results showed the predominant concentration of the Botrytis airborne spores, mainly from the beginning of the Inflorescence emerge phenological stage (S-5) until the end of the Flowering phenological stage (S-6). Erysiphe and Plasmopara airborne spore peak concentrations were more localised around Flowering (S-6) and Development of fruits (S-7) phenological stages. We applied a Spearman’s correlation test and a Principal Component Analysis to determine the influence of the meteorological parameters on the concentration of airborne spores. Taking into account the variables with the highest correlation coefficient, we developed multiple regression models to forecast the phytopathogenic fungal spore concentrations. The Botrytis model regression equation explained between 59.4−70.9% of spore concentration variability. The Erysiphe equation explained between 57.6−61% and the Plasmopara explained between 39.9−55.8%. In general, we found better prediction results for mean daily concentrations than sporadic spore peaks.

Cyclophilins (CYPs), a highly-conserved family of proteins, belong to a subgroup of immunophilins. Ubiquitous in eukaryotes and prokaryotes, CYPs have peptidyl-prolyl cis−trans isomerase (PPIase) activity and have been implicated as virulence factors in plant pathogenesis by oomycetes. We identified 16 CYP orthogroups from 21 diverse oomycetes. Each species was found to encode 15 to 35 CYP genes. Three of these orthogroups contained proteins with signal peptides at the N-terminal end, suggesting a role in secretion. Multidomain analysis revealed five conserved motifs of the CYP domain of oomycetes shared with other eukaryotic PPIases. Expression analysis of CYP proteins in different asexual life stages of the hemibiotrophic Phytophthora infestans and the biotrophic Plasmopara halstedii demonstrated distinct expression profiles between life stages. In addition to providing detailed comparative information on the CYPs in multiple oomycetes, this study identified candidate CYP effectors that could be the foundation for future studies of virulence.

Induction of plant resistance against pathogens by defense elicitors constitutes an attractive strategy to reduce the use of fungicides in crop protection. However, all elicitors do not systematically confer protection against pathogens. Elicitor-induced resistance (IR) thus merits to be further characterized in order to understand what makes an elicitor efficient. In this study, the oligosaccharidic defense elicitors H13 and PS3, respectively, ineffective and effective to trigger resistance of grapevine leaves against downy mildew, were used to compare their effect on the global leaf metabolism. Ultra high resolution mass spectrometry (FT-ICR-MS) analysis allowed us to obtain and compare the specific metabolic fingerprint induced by each elicitor and to characterize the associated metabolic pathways. Moreover, erythritol phosphate was identified as a putative marker of elicitor-IR. [ABSTRACT FROM AUTHOR]

The virulence of the downy mildew pathogen increased during the last period and new virulent races of this fungus appear. Thus it is essential to know data about the presence and distribution of the pathotypes. In Europe, an increasing number of the pathotypes, have been identified. In Romania we identified eight races of the pathogen. They are not present in all areas cultivated with sunflower, in some areas being present only five races, in other six or seven. Using the sources of resistance to Plasmopoara halstedii pathogen, for the most virulent races present now in Europe we have introduced genes of resistance in the best lines from our germplasm collection. The testing of some sunflower hybrids with different degree of resistance to downy mildew has showed that there is difference in the pathogen attack degree, depending on the climatic conditions in the years and locations. [ABSTRACT FROM AUTHOR]

Sunflower line with resistance for downy mildew (Ha-26R) and susceptible line (Ha-26S) were inoculated with the suspension of Plasmopara halstedii zoosporangia, race 730, in the phase of first pair of leaves. The expression of defense related genes was investigated in the time period of 2 to 96 h after treatment. Several categories of defense-related genes: signalization (EDS1 and EDR1); H2O2 producing (Hacaox and Haoxox); antioxidative response (SODc and SODp), pathogenesis related (chi, PAL, PR5) were examined. Most examined defense related genes were constitutive with higher expression in resistant line. However, in response to secondary downy mildew infection six genes were upregulated. Upregulation of HaEDS1 signaling gene 2 h after infection indicates that SA mediated response is activated. Pathogenesis related genes: chitinase and PR5, were also upregulated in the earliest time point. Other defense related genes: SODp, Caox and OxOx were sequentially upregulated from 4 to 48 h after infection in resistant line. Our results indicate that the early response of defense related genes to secondary downy mildew infection, resembles to hypersensitive-like reaction and is connected with resistance conferred by Pl6 gene. According to our results resistance to secondary infection is characterized with earlier upregulation of PR5 in comparison to primary infection. [ABSTRACT FROM AUTHOR]

Geranium phaeum is a popular ornamental plant in Europe. Downy mildew disease caused by Plasmopara was found on this plant once 50 years ago in Poland, but at that time attributed to the native species, Plasmopara pusilla. Here we report the recurrence of downy mildew disease on G. phaeum in Germany. Molecular phylogenetic analysis and morphological investigations revealed that the causal agent of the new outbreak is P. wilsonii, but not P. pusilla. Plasmopara wilsonii had previously been found only in the USA and Korea on various hosts of Geranium. The presence of P. wilsonii on G. phaeum in Europe should be closely monitored, as downy mildew caused by this species probably has the potential to become an important emerging disease on its ornamental host, especially, as also the native G. molle is able to sustain the pathogen. [ABSTRACT FROM AUTHOR]

Plasmopara halstedii and Plasmopara viticola are the causative agents of downy mildew of two economically important crops, sunflower and grapevine, respectively. These phylogenetically related oomycetes are obligate biotrophs belonging to Peronosporales but have different pathological profiles. Despite the economic importance of diseases caused by both Plasmopara, genomic resources are very limited and their effector repertoire is unknown. In this study parallel transcriptome sequencing of P. halstedii and P. viticola was performed, and a Plasmopara species cDNA database (PlasmoparaSp) released containing 46 000 clusters. In oomycetes, two classes of effectors are translocated into the host cytoplasm, the RXLRs and the CRNs. The PlasmoparaSp database was screened in order to identify the repertoire of expressed effectors used by both Plasmopara species; about 50 putative RXLR and 60 CRN were identified for each. These effectors were compared within both species and with seven publicly available oomycete species representative of Peronosporales and Albuginales. Sequence analyses revealed the presence of 55 RXLR families, 12 of them shared by both Plasmopara, and 19 showing amino acid conservation with predicted peptides from at least one oomycete species. Analyses of Plasmopara spp. CRN C-terminal variable regions revealed sequence conservation inside Plasmopara spp. and across oomycetes, with the exception of Hyaloperonospora arabidopsidis. Finally, the analyses confirmed the presence of eight CRN C-terminal domains described in Phytophthora infestans and identified CRN effectors showing similarity to serine proteases. Species-specific effectors were identified that may be involved in host specificity, as well as effectors conserved among oomycetes that might play important roles in the pathogen biology. [ABSTRACT FROM AUTHOR]

Background: Downy mildews are the most speciose group of oomycetes and affect crops of great economic importance. So far, there is only a single deeply-sequenced downy mildew genome available, from Hyaloperonospora arabidopsidis. Further genomic resources for downy mildews are required to study their evolution, including pathogenicity effector proteins, such as RxLR effectors. Plasmopara halstedii is a devastating pathogen of sunflower and a potential pathosystem model to study downy mildews, as several Avr-genes and R-genes have been predicted and unlike Arabidopsis downy mildew, large quantities of almost contamination-free material can be obtained easily. Results: Here a high-quality draft genome of Plasmopara halstedii is reported and analysed with respect to various aspects, including genome organisation, secondary metabolism, effector proteins and comparative genomics with other sequenced oomycetes. Interestingly, the present analyses revealed further variation of the RxLR motif, suggesting an important role of the conservation of the dEER-motif. Orthology analyses revealed the conservation of 28 RxLR-like core effectors among Phytophthora species. Only six putative RxLR-like effectors were shared by the two sequenced downy mildews, highlighting the fast and largely independent evolution of two of the three major downy mildew lineages. This is seemingly supported by phylogenomic results, in which downy mildews did not appear to be monophyletic. Conclusions: The genome resource will be useful for developing markers for monitoring the pathogen population and might provide the basis for new approaches to fight Phytophthora and downy mildew pathogens by targeting core pathogenicity effectors. [ABSTRACT FROM AUTHOR]

Plasmopara halstedii virus (PhV) is a ss(+)RNA virus that exclusively occurs in the sunflower downy mildew pathogen Plasmopara halstedii , a biotrophic oomycete of severe economic impact. The virus origin and its genomic variability are unknown. A PCR-based screening of 128 samples of P. halstedii from five continents and up to 40 y old was conducted. PhV RNA was found in over 90 % of the isolates with no correlation to geographic origin or pathotype of its host. Sequence analyses of the two open reading frames (ORFs) revealed only 18 single nucleotide polymorphisms (SNPs) in 3873 nucleotides. The SNPs had no recognizable effect on the two encoded virus proteins. In 398 nucleotides of the untranslated regions (UTRs) of the RNA 2 strand eight additional SNPs and one short deletion was found. Modelling experiments revealed no effects of these variations on the secondary structure of the RNA. The results showed the presence of PhV in P. halstedii isolates of global origin and the existence of the virus since more than 40 y. The virus genome revealed a surprisingly low variation in both coding and noncoding parts. No sequence differences were correlated with host pathotype or geographic populations of the oomycete. [ABSTRACT FROM AUTHOR]

Specific scope This Standard describes a diagnostic protocol for Plasmopara halstedii. Specific approval and amendment Approved in 2008-09. Revised in 2014-06 [ABSTRACT FROM AUTHOR]

Morphological characteristics were studied in severalPlasmopara halstedii(sunflower downy mildew) isolates of seven races. Zoosporangia and sporangiophores were analysed forP. halstediiisolates. Significant morphological differences were revealed for all pathogen isolates. Mean oval proportion was 78.3?±?3.5%, mean zoosporangium size was 459.2?±?30.2??m2, mean sporangiophore length was 556.9?±?36.2??m and mean sporangiophore width was 10.3?±?0.9??m. Our results provide evidence that the morphology of pathogen do not correlate with both pathogenic and genetic variation. [ABSTRACT FROM PUBLISHER]

The specificity of the two components of pathogenicity: virulence and aggressiveness and its relationship with genetic variability were analysed in a localPlasmopara halstedii(sunflower downy mildew) population. Pathogenic and molecular analyses were carried out on seven isolates including five progeny isolates of five races arising from two parental races 100 and 710.P. halstediiisolates showed significant differences for all aggressiveness criteria and important genetic variations. Three cases of relationship between virulence and aggressiveness for progeny isolates as compared with parental ones were found as positive, negative or uncorrelated. For solving the specificity of these cases, relationship between the two components of pathogenicity among the isolates of three different races localised in the same genetic clade was positive. The hypothesis explaining these cases is discussed. [ABSTRACT FROM AUTHOR]

Lines resistant to Plasmopara halstedii, Phomopsis helinthi, Septoria helianthi and Orobanche cumana (race E and G) were obtained from the Bulgarian susceptible fertility restorer lines 2574 R, 147 R, 374 R, 381 R, 377 R, American line RHA-857 and Bulgarian line with normal cytoplasm 197 B. Lines were developed using embryo culture method in combination with ultra sonic and gamma irradiation at sunflower immature zygotic embryos. All investigated lines possessed 100% resistance to diseases and parasite Orobanche. Some of the new lines showed very good combining ability. Line 12002 R developed through embryo culture method at immature zygotic embryos in combination with gamma irradiation at dose 8 Gy is paternal component of commercial hybrid Rada. Line 12003 R developed through embryo culture method at immature zygotic embryos in combination with ultra sonic at dose 25.5 W cm−2 for 1 min is paternal component of commercial hybrid Yana. Hybrids Rada and Yana possessing immunity to parasite Orobanche cumana race E and G, respectively; immunity to Plasmopara helianhi - races 300, 330, 700 and 731; resistance to Phomopsis; immunity to Macrophomina and tolerance to Phoma. Our results showed that mutagenesis in sunflower can be successfully applied to develop new lines suitable for use as parental components of new hybrids. [ABSTRACT FROM AUTHOR]

Highlights: [•] We performed a successful RNA virus transmission in Oomycetes. [•] The virus causes hypovirulence effects in P. halstedii. [•] The virus reduces systemic infections of P. halstedii on H. annuus. [ABSTRACT FROM AUTHOR]

Extension of areas cultivated with sunflower within our country during the last decade to over 800 ths. Ha and up to over 1 million Ha in 1999, as consequence of the high demand on the internal and external market, is representing a real danger. This is due to the fact that the 6-7 years return period for the same lot can no more be observed. Such a return period is required due to the continuance in the soil of the several pathogen agents as Plasmopara helianthi Novot, Sclerotinia sclerotiorum (Lib) de Bary, Sclerotinia bataticola Taub. Research has been performed on a brown luvic soil. The precursory culture has been wheat. The experiments have been tri-factorial, factor A has been the cultivated hybrid (a1 -- RP64F50 --; a2 PR64A89, factor B -- the agricultural fond (b1 -- N50P100K100; b2 -- N100P100K100), and factor C cultivation density (c1 -- 45.000 plants/ha; c2-50.000 plants/ha). Experiences have been performed during the experimental cycle 2010-2012. The studied hybrids have genetic strength to blight attacks (Plasmopara helianthi), species 304, already existing in our country. These hybrids are tolerant to Phomopsis and Sclerotinia, resistant to fall and breakage, resistant to dryness and heat, highly productive and having high content of oil. The crop results are revealing the superiority of PR64A89 hybrid that has overcome by 9% the crop of PR64F50.n Increasing of nitrogen dose from N50 to N100 on the constant usage of P100K100 has increased the crop by 14%. Increasing the density from 45,000 to 50,000 plants/ha has lead to crop decreasing by 12%. Thousand seeds mass has been negatively influenced by increasing the density, on both fertilization levels, on both hybrids, oscillating between 58 and 61 g. at PR64F50 hybrid and between 60 and 65 g to PR64SA89 hybrid. A similar tendency has been manifested and the hectoliter mass has been situated between 43 - 45 kg/hl at PR64F50 and between 38-43 kg/hl at PR64A89. The content of oil in PR64F50 hybrid has decreased following the doubling of nitrogen dose from 45 to 42% and to PR64A89 46-44 %. [ABSTRACT FROM AUTHOR]

Resistance of grape downy mildew caused by Plasmopara viticola against different fungicide classes has been reported in Europe. The main objective of the present study was to measure the sensitivity status of P. viticola populations to four fungicide active ingredients used in the Luxembourgian vine-growing region and to investigate the presence of resistant populations. Thus, leaf samples with downy mildew symptoms were collected in 19 vineyards along the river Moselle in 2010 and 2011. Samples were analysed in both years for carboxylic acid amides (CAA) and the quinone outside inhibitors (QoI), using a microplate conidia growth inhibition assay. In 2011, a leaf disc assay was used in addition to determine the sensitivity profile of the sampled populations to phenylamides (PA) and to cymoxanil. Results showed that in average, 64% (2010) or 81% (2011) of the zoospores were resistant to QoI fungicides, and 91% (2010) or 85% (2011) to the CAA fungicide dimethomorph. Furthermore, in 2011, all populations were classified as extremely resistant to the PA fungicide kiralaxyl, indicating that the sampled Luxembourgian populations contained at least 50% of resistant strains. No population was controlled by cymoxanil at the rate of 100 mg/l. In average, 84% of the populations showed a minimum inhibitory concentration (MIC) between 300-800 mg/l, and 16% a MIC reaching 800 mg/l. The presented results indicate that fungicide resistance against CAAs, QoIs, PAs and cymoxanil is currently widespread in the Luxembourgian wine-growing area. [ABSTRACT FROM AUTHOR]

Pathogenic, morphological and genetic variation was studied in 35 Plasmopara halstedii (sunflower downy mildew) isolates of different races. Virulence spectrum was analyzed in sunflower hybrids carrying effective Plgenes. Aggressiveness was analyzed in one sunflower inbred line showing a high level of quantitative resistance. There were differences in virulence spectrum for pathogen isolates. Index of aggressiveness was calculated for each isolate and two groups were revealed as more aggressive isolates of 100 and 3xx races, and less aggressive isolates of 7xx races. Significant morphological differences were found in zoosporangia and sporangiophores morphology. Genetic relationships were detected between the pathogen isolates using 12 EST-derived markers. Five multilocus genotypes (MLG) were identified among 35 P. halstedii isolates. Our results did not show a correlation between pathogen variation and both morphological and genetic characteristics. [ABSTRACT FROM AUTHOR]

In 2007-2012 the first detailed study of P. halstedii distribution and severity was performed in the Czech Republic by monitoring altogether 128 localities. Incidence of the pathogen was recorded at seven localities in south-eastern (Central and South Moravia) and central parts (East and Central Bohemia) of the country; at only four localities the occurrence of sunflower downy mildew symptoms and pathogen sporulation were recorded repeatedly. In all cases the primary infection prevailed, and the severity of infections was rather low. The majority of records were for sunflower experimental fields (e.g. fields of Central Institute for Supervising and Testing in Agriculture. Brno-Chrlice, Czech Republic), one record came from a commercial field and one record from a hobby field. Results of surveys indicate that reservoirs of primary inoculum likely exist in the soil contaminated by P. halstedii oospores in these habitats, but additional transfer by infected seed may be possible. Historical and geographical consequences of recorded infections are discussed, as well as virulence variation in the Czech pathogen populations which is currently in the process of investigation. [ABSTRACT FROM AUTHOR]

Sunflower downy mildew is one of the most important and destructive diseases of this crop in WestAzarbaijan. The disease causes epidemic damages and yield losses at favorite environmental conditions for the pathogen activity. Application of disease resistant cultivars is considered as one of the effective control methods. During the growing season of 2009 in West-Azarbaijan, infected sunflower plants were collected and used as a source of Plasmopara halstedii for inoculation of standard differential lines to identify the variation of pathogenicity. The resistance of seven open-pollinating cultivars and two hybrids of sunflower to the dominant race (race 100) of P. halstedii, was evaluated employing the whole seedling immersion (WSI) method in the greenhouse. In this investigation, nine macroscopic disease symptoms including damping-off, sporulation on cotyledons and leaves, sporulation on leaves, stunting, sporulation on cotyledons, mosaic on leaves, deformation of leaves, lesion on hypocotyls and root reduction on the inoculated plants were considered for disease rating and calculating the disease severity index (D.S.I). The experiment was conducted in three replications for each cultivar. The analysis of variance (ANOVA) was performed and the means were compared using Duncan multiple range test (P = 0.05) in SAS ver. 9.1 (SAS institute Inc., Cary, NC.). According to the analysis of variance (ANOVA) for disease severity index, cultivars and hybrids were classified into five significantly different groups (P< 0.05): resistant, moderately resistant, moderately susceptible, susceptible, and highly susceptible. Cultivars Lakumka and Master were in the same group as resistant cultivars, whereas Record was highly susceptible. [ABSTRACT FROM AUTHOR]