Tropic failure of Phyllactinia corylea contributes to the mildew resistance of mulberry genotypes

Different mulberry genotypes show great variation in their resistance to the powdery mildew Phyllactinia corylea. Conidial germination and hyphal growth of P. corylea on the leaf surface of two susceptible mulberry genotypes, viz., Kanva 2 (K2) and Victory 1 (V1) varieties of Morus indica, and on two resistant species, viz,, M. laevigata and M. serrata were studied by scanning electron microscopy. Conidial germination and growth of germ tubes were normal on all the leaves. The hyphae of P. corylea identify stomata on host leaves by their topographical features to produce the stomatopodia precisely over them. The holes and/or the grooves of stomata appear to provide the signals for the initiation of stomatopodia and similar structures are erratically developed over many local depressions or grooves on leaf surface. The abaxial surface of K2 leaf is smooth without prominent undulations of epidermal cell surface, and the stomata are flush with the leaf surface. Although successful penetration is also achieved on V1 leaf, its slightly undulated surface occasionally provides inaccurate tropic signals to the hyphae, inducing the development of stomatopodia away from the stomata. The leaf surfaces of M. laevigata and M. serrata are very rough with highly sculptured cuticle and abundant epidermal outgrowths. Stomata mostly remain sunken or hidden amidst the cuticular ornamentations and the hyphae fail to recognise the precise signals from them. As the surface architecture of the leaves provides many immense sources of tropic signals, stomatopodia are often produced over local depressions or grooves. In these cases the fungus fails to penetrate the leaf, does not develop beyond 24 h and penetration is rarely achieved on the leaves of the resistant plants. The study indicates that the stimulatory effect of the leaf surface topography of resistant varieties misleads the pathogen from successful penetration, thus contributing to the plant's resistance.     

Tropic failure of Phyllactinia corylea contributes to the mildew resistance of mulberry genotypes

Different mulberry genotypes show great variation in their resistance to the powdery mildew Phyllactinia corylea. Conidial germination and hyphal growth of P. corylea on the leaf surface of two susceptible mulberry genotypes, viz., Kanva 2 (K2) and Victory 1 (V1) varieties of Morus indica, and on two resistant species, viz., M. laevigata and M. serrata were studied by scanning electron microscopy. Conidial germination and growth of germ tubes were normal on all the leaves. The hyphae of P. coryleaidentify stomata on host leaves by their topographical features to produce the stomatopodia precisely over them. The holes and/or the grooves of stomata appear to provide the signals for the initiation of stomatopodia and similar structures are erratically developed over many local depressions or grooves on leaf surface. The abaxial surface of K2 leaf is smooth without prominent undulations of epidermal cell surface, and the stomata are flush with the leaf surface. Although successful penetration is also achieved on V1 leaf, its slightly undulated surface occasionally provides inaccurate tropic signals to the hyphae, inducing the development of stomatopodia away from the stomata. The leaf surfaces of M. laevigata and M. serrata are very rough with highly sculptured cuticle and abundant epidermal outgrowths. Stomata mostly remain sunken or hidden amidst the cuticular ornamentations and the hyphae fail to recognise the precise signals from them. As the surface architecture of the leaves provides many immense sources of tropic signals, stomatopodia are often produced over local depressions or grooves. In these cases the fungus fails to penetrate the leaf, does not develop beyond 24 h and penetration is rarely achieved on the leaves of the resistant plants. The study indicates that the stimulatory effect of the leaf surface topography of resistant varieties misleads the pathogen from successful penetration, thus contributing to the plant's resistance.This revised version was published online in October 2005 with corrections to the Cover Date.     

Control of pearl millet downy mildew caused by Sclerospora graminicola with systemic fungicides in an artificially-contaminated plot

Among four fungicides, viz. metalaxyl (two formulations), fosetyl-Al, pro-pamocarb and cyomaxanil tested in vitro against sporangial germination inhibition of Sclerospora graminicola, cyomaxanil was found to be most inhibitory. In an artificially contaminated plot, when used as seed treatment or foliar spray for the control of downy mildew of pearl millet, only metalaxyl was effective. Metalaxyl 25 (Ridomil) and metalaxyl 35 (Apron) seed treatments protected the pearl millet plants from downy mildew up to 30 days. As a foliar spray, metalaxyl 25 used once at 20 days or twice after 20 and 38 days of plant growth gave less disease at harvest time. Seed treatment (metalaxyl 25 or 35) followed by one metalaxyl 25 spray was found to be effective in controlling the downy mildew. These treatments improved the growth of plants and yield significantly.     

Studies on Foliar Penetration: 2. THE ROLE OF LIGHT IN DETERMINING THE PENETRATION OF 2,4 DICHLOROPHENOXYACETIC, ACID

A further study has been made of the factors determining thelevel of penetration of 2,4-dichlorophenoxyacetic acid (2,4-D)into leaves. The technique involves the use of leaf disks and2,4-D containing carbon-14 in the carboxyl group. For Phaseolus vulgaris the influence of the pH of the appliedsolution is greater in the light than in the dark. Between 0and 1,000 f.c. at 27° C there is a small increase in therate of penetration into the abaxial surface. Under these conditionsthe rates remain constant up to 56 hours. This linear relationshipholds for concentrations ranging from 100 to 1,000 mg/l, andthe rate of penetration is directly proportional to the concentration.For intensities in excess of 1,000 f.c. the light response ismarkedly different: over the first few hours there is a steadyand relatively slow rate of penetration which is followed bya second phase when the rate is greatly accelerated. This acceleratedrate can be reversed by transferring the disks to darkness,and does not take place at 1° C. Likewise, if excised disksare left for more than one hour in either the light or the darkbefore applying 2,4-D then there is subsequently no phase ofaccelerated penetration. The course of penetration into theadaxial surface exhibits no accelerated rate, and compared tothe abaxial surface the rates are lower. For leaves of Ligustrum ovalifolium, which lack stomata on theadaxial surface, the rates of penetration at 27° C intoboth surfaces remain constant in either light or darkness. Forboth the adaxial and abaxial surfaces, the rate progressivelyincreases from 0 to; 2000 f.c. and there is no phase of acceleratedpenetration. Penetration into the adaxial surface is less. At1° C the rates for both surfaces in either light or darknessare depressed. If disks of Phaseolus are irradiated with ultraviolet light,subsequent penetration is markedly depressed in the light at27° C, but in the dark or at 1° C it is enhanced. On the basis of these findings it is concluded that both physicaland metabolic factors control the rate of penetration of 2,4-DTransport through the cuticle will be dependent on adsorptionand the length of the diffusion paths. Once diffusion gradientshave been established between the surface of the cuticle andthe outer surface of the cytoplasm in the epidermal cells, thesteepness will be dependent on the rates at which 2,4-D is eitherconverted into some metabolite or moved away from the surfaceor into other cells. The relative importance of physical andmetabolic process will be dependent on the permeability andthickness of the cuticle and the level of metabolic activity.The possible role of ectodesmata in determining both the lengthand steepness of the diffusion paths is discussed.     

不同品种葡萄抗霜霉病特性与叶片POD、PPO活性关系的研究

在霜霉病盛发期,对8804、梅尔诺、品丽珠3个葡萄品种(系)叶片中的PPO和POD活性变化进行了测定.结果显示,8804的PPO和POD活性较大,并保持相当长时间的高活性值,而梅尔诺、品丽珠叶片中PPO和POD活性较小;8804的PPO酶活性变化范围高于其它2个品种,但POD酶活性变化范围却低于后者.葡萄叶片中PPO和POD活性与葡萄霜霉病抗性之间存在一定的相关性,且不同抗感品种间PPO和POD酶活性存在极显著差异.研究结果表明,8804较梅尔诺、品丽珠对霜霉病具有较强的抗性.     

Synergistic effects of Trichoshield on enhancement of growth and resistance to downy mildew in pearl millet

Trichoshield, a talc formulation consisting of spores of Trichoderma harzianum, Trichoderma lignorum, Gliocladium virens and Bacillus subtilis was tested, following different application methods, for its ability to promote growth of pearl millet plants and to induce resistance to downy mildew of pearl millet. Under laboratory conditions, trichoshield seed treatment enhanced seed germination and seedling vigor of pearl millet significantly over the control; under greenhouse conditions vegetative growth parameters like height, fresh and dry weight, leaf area and number of tillers were significantly enhanced over the control: Trichoshield formulation offered greater protection against downy mildew in comparison with individual strains of T. harzianum, T. lignorum, G. virensand B. subtilis. Among the methods of application, foliar spray was found to be a more efficient delivery method than seed treatment or slurry treatment. Combinations of foliar spray with seed treatment and slurry treatment produced the same effect as foliar spray alone. Under field conditions, trichoshield treatment enhanced reproductive parameters like number of earheads, length and girth of earheads, 1000 seed weight and yield significantly over the control. Days required for 50% flowering was reduced by 4 days compared to the control. Yield enhancement of 28% over the control was highly significant. Trichoshield treatment offered protection ranging from 52 to 71% under field conditions, depending on the application method. However, the chemical fungicide metalaxyl Apron provided the highest protection against downy mildew, both under greenhouse and field conditions.     

Effect of wheat phosphorus status on leaf surface properties and permeability to foliar-applied phosphorus

Aims

This study aimed to analyse the effect of phosphorus (P) nutritional status on wheat leaf surface properties, in relation to foliar P absorption and translocation.

Methods

Plants of Triticum aestivum cv. Axe were grown with three rates of root P supply (equivalent to 24, 8 and 0 kg P ha^?1) under controlled conditions. Foliar P treatments were applied and the rate of drop retention, P absorption and translocation was measured. Adaxial and abaxial leaf surfaces were analysed by scanning and transmission electron microscopy. The contact angles, surface free energy and work-of-adhesion for water were determined.

Results

Wheat leaves are markedly non-wettable, the abaxial leaf side having some degree of water drop adhesion versus the strong repulsion of water drops by the adaxial side. The total leaf area, stomatal and trichome densities, cuticle thickness and contact angles decreased with P deficiency, while the work-of-adhesion for water increased. Phosphorous deficient plants failed to absorb the foliar-applied P.

Conclusions

Phosphorous deficiency altered the surface structure and functioning of wheat leaves, which became more wettable and had a higher degree of water drop adhesion, but turned less permeable to foliar-applied P. The results obtained are discussed within an agronomic and eco-physiological context.     

Foliar Penetration of Succinic Acid-2,2-dimethylhydrazide: Mechanism and Rate Limiting Step

The foliar penetration of succinic acid-2,2-dimethylhydrazide (SADH) into primary leaves of bean ( Phaseolus vulgaris L. cv. Blue Lake) was studied using detached leaves and a leaf disc method. SADH penetration was linear with time and directly related to concentration and the fraction of non-ionized SADH molecules in the treating solution. The addition of a surfactant, polyoxyethylene sorbitan monolaurate, increasing temperature and light enhanced penetration. Surfactant and light enhanced penetration are discussed in relation to increased wetting and area of contact over guard and accessory cells and the greater permeability of the cuticular ledges in open than in closed stomata. Evidence is presented that foliar penetration of SADH takes place by diffusion controlled by the cuticular membrane. Metabolic processes were not rate limiting.     

Thermal imaging of cucumber leaves affected by downy mildew and environmental conditions

Pathogenesis of Pseudoperonospora cubensis causing downy mildew of cucumber resulted in changes in the metabolic processes within cucumber leaves including the transpiration rate. Due to the negative correlation between transpiration rate and leaf temperature, digital infrared thermography permitted a non-invasive monitoring and an indirect visualization of downy mildew development. Depending on the stage of pathogenesis and the topology of chloroses and necroses, infection resulted in a typical temperature pattern. Spatial heterogeneity of the leaf temperature could be quantified by the maximum temperature difference (MTD) within a leaf. The MTD increased during pathogenesis with the formation of necrotic tissue and was related to disease severity as described by linear and quadratic regression curves. Under controlled conditions, changes in temperature of infected leaves allowed the discrimination between healthy and infected areas in thermograms, even before visible symptoms of downy mildew appeared. Environmental conditions during thermographic measurement, in particular air temperature and humidity, as well as water content and age of the leaf influenced the temperature of its surface. Conditions enhancing the transpiration rate facilitated the detection of changes in leaf temperature of infected leaves at early stages of infection. As modified by environmental conditions, MTD alone is not suitable for the quantification of downy mildew severity in the field.     

Germination of Erysiphe gratninis f.sp. hordei conidia on barley leaves

Germination of Erysiphe graminis f.sp. hordei conidia on leaves of several barley cultivars was studied in the laboratory. On both detached leaves and intact plants, within 48 h of inoculation a higher proportion of conidia had germinated on the basal and middle portions of the adaxial leaf surface than on the corresponding portions of the abaxial surface. Such differences between surfaces were not observed near the leaf tip. Similar results were obtained with all the cultivars and growth stages tested, and with five isolates of E. graminis, and are consistent with the observation that there is usually less powdery mildew on the abaxial than the adaxial surface of barley leaves. With most of the barley genotype/mildew isolate combinations tested, within 48 h of inoculation higher proportions of conidia germinated on seedlings and juvenile plants than on older plants. Inherited characteristics which affect spore germination on the leaf surface may be important factors in the development of adult-plant resistance of barley to powdery mildew, particularly in certain genotypes.     

内生枯草芽孢杆菌JL4在葡萄叶上的定殖及其对葡萄霜霉病的防治

为了明确枯草芽孢杆菌JL4在葡萄叶表面和内部的定殖情况,研究定殖与防治效果的关系,采用电击转化的方法将含有GFP基因的质粒pGFP78导入枯草芽孢杆菌JL4中,并得到成功表达GFP 的生防菌JL4-gfp,测试了标记菌株的稳定性及其对葡萄霜霉病菌的抑制作用.采用叶片喷雾法接种,用抗生素平板稀释分离回收,检测生防菌JL4-gfp在葡萄叶片的定殖情况,并将采回的叶片在室内接种葡萄霜霉菌孢子囊悬浮液进行生防测定.结果表明: 标记菌株在经过10次传代培养后,仍具有良好的发光表型,能稳定表达GFP蛋白,并且标记菌株JL4-gfp对葡萄霜霉菌保持了原有的抑菌作用;用抗生素平板稀释分离回收,检测到JL4-gfp菌株在葡萄叶片表面的定殖量在接种后的0、3和7 d分别为3.6×10⁵、2.7×10⁵和3.1×10³ CFU·g^-1;叶片内部的定殖在接种3 d后达到最大(9.6×10⁴ CFU·g^-1),然后下降,14 d后已经检测不到接种菌株;室内生防测定结果显示,喷雾后3 d对葡萄霜霉病的防治效果达88.0%以上,但7 d后则无明显防效.JL4-gfp的定殖量与其防治葡萄霜霉病的效果呈正相关,其有效定殖量临界值为10⁵ CFU·g^-1.     

Studies on Foliar Penetration: IX. PATTERNS OF PENETRATION OF 2,4-DICHLOROPHENOXYACETIC ACID INTO THE LEAVES OF DIFFERENT SPECIES

The comparative patterns of penetration of 2,4-dichlorophenoxyaceticacid (2,4-D) into the leaves of Phaseolus vulgaris, Zea mays,Pisum sativum, Beta wlgaris, Helianthus annuus and Gossypiumhirsuium have been examined. Save for Zea and Gossypium where there is little change withthe stage of leaf development the rates of penetration intoboth surfaces decrease as the leaf matures. The relative ratesare dependent on the species and the age of the leaf but thereare differences between the surfaces. In Phaseolus the characteristicsof primary leaves differ from those of trifoliate leaves sinceonly in immature trifoliate leaves is penetration into the adaxialsurface greater. In darkness the rates of penetration over 24 h remain constantor fall but slightly for all species. Light consistently promotespenetration but with Beta there is a lag before entry is acceleratedinto the abaxial surface as has previously been reported foryoung primary leaves of Phaseolus. For the remaining speciesthe courses of penetration in both light and darkness into bothsurfaces follow similar patterns. As the light intensity isincreased entry is enhanced but the limit of response variesbetween species, between surfaces within species, and in trifoliateleaves of Phaseolus with age. For the six species the order of the relative rates of entryis closely similar whether comparisons are made in light ordarkness or between abaxial and adaxial surfaces: viz. Zea >Helianthus > Phaseolus (primary) > Phaseolus (trifoliate)> Pisum = Beta = Gossypium. The observed specific differencesare discussed in relation to variations in leaf structure, theproperties and thickness of the cuticle and the physiologicaland metabolic processes which influence transport within theepidermal tissues after it has passed through the cuticle bydiffusion.     

Control of Downy Mildew, Plasmopara viticola (de Bary) Berlese et de Toni, on Grapevine Leaves through Water Extracts from Composted Organic Wastes

Watery extracts of composted manure-straw-soil mixtures induced increased resistance of grapevine leaves against downy mildew, Plasmopara viticola, if applied by dipping or spraying. The extracts had no direct fungicidal or fungitoxic effects.     

Wheat leaf properties affecting the absorption and subsequent translocation of foliar-applied phosphoric acid fertiliser

Background and aims

Although foliar fertilisation using liquid forms of phosphorus (P) is not a new concept, its adoption has been hindered by a limited understanding of the variability in performance of fluid forms of foliar P applied to broadacre crops. There is a need to identify how the surface structure of leaves influences the absorption and subsequent translocation of foliar-applied P in above ground plant parts.

Methods

This study examined the surface properties of wheat leaves using scanning electron microscopy and measured the recovery of foliar-applied fertiliser that was labelled with either ³²P or ³³P from both the adaxial (upper) and abaxial (lower) leaf sides into untreated plant parts.

Results

We found that the adaxial leaf surface absorbed and translocated more foliar-applied P away from the treated leaf than the abaxial surface, likely related to the higher abundance of trichomes and stomata present on that side of the leaf. The recovery of the foliar-applied fertiliser varied with rate and timing of application; ranging from <30 % to as much as 80 % of the adaxial-applied fertiliser translocated from the treated leaf into the wheat ear.

Conclusions

This study demonstrated that the differences in surface morphological features between leaf sides influenced the combined absorption and subsequent translocation of foliar-applied P in the above ground plant parts. This is due to a direct effect on the foliar pathway and/or due to differences in wettability affecting both the leaf coverage and drying time of fertilisers on the leaves. Although foliar fertilisation in this study contributed less than 10 % of the total P in the plant, it provided a more efficient pathway for P fertilisation than soil-applied P.     

Development of SSR markers linked to QTL reducing leaf hair density and grapevine downy mildew resistance in <Emphasis Type="Italic">Vitis vinifera</Emphasis>

Dense leaf hairs of grapevines have been known to act as a preexisting defense structure for preventing the incidence of grapevine downy mildew, because the pathogen, Plasmopara viticola, needs water to invade grapevines, and water is repelled by a hydrophobic surface due to dense leaf hairs. In the present study, we performed regression analyses of downy mildew resistance with leaf hair density using hybrids of Vitis labrusca origin and confirmed the effect of leaf hairs. Reducing the repelling effect of leaf hairs by detergent application canceled the effect of leaf hair, which confirmed the hypothesis. Thereafter, based on QTL analyses in the population of V. vinifera ‘Muscat of Alexandria’ × the interspecific hybrid ‘Campbell Early,’ we identified a major locus in linkage group (LG) 5 of ‘Muscat of Alexandria’ controlling leaf hair density. This locus was previously reported as a small effect QTL for downy mildew resistance, however we found that the locus had high LOD scores explaining 71.9%–78.5% of the phenotypic variance of leaf hairs. Moreover, this locus was detected as a QTL for downy mildew resistance. The effect of this locus was confirmed in two other hybrid populations. Finally, we could successfully identify three traditional V. vinifera table grapes ‘Muscat of Alexandria,’ ‘Katta Kurgan,’ and ‘Parkent’ as the origin of the allele linked to hairlessness by defining the SSR haplotypes. The use of this locus for marker-assisted selections would be a promising strategy for producing grapevines with resistance by preexisting defense structure.     

苦瓜叶片结构与白粉病抗性的关系

以不同抗白粉病的苦瓜品系幼苗为材料,对它们的叶片及上下表皮厚度、栅栏组织及海绵组织厚度、叶片结构紧密度及疏松度、蜡质含量、比叶重、气孔及茸毛密度等叶片结构进行观察比较,探讨苦瓜白粉病抗性与其主要叶片结构指标的关系。结果显示:（1）抗病苦瓜品系叶片的蜡质含量显著高于感病品系,与病情指数呈显著负相关关系,蜡质层是其抵抗和延迟病原菌侵入的一个有力结构屏障。（2）感病品系叶片的气孔和叶背面茸毛数量显著多于抗病品系,且叶背面的气孔及茸毛密度与病情指数呈显著正相关关系,即气孔和茸毛越少越抗病。（3）抗病苦瓜品系的叶片栅栏组织以及海绵组织排列整齐、紧密,而高感品系的叶片组织出现大量孔隙,较难观察到完整细胞。（4）抗病品系叶片厚度、下表皮厚度、栅栏组织厚度、叶片结构紧密度明显高于感病品系,而感病品系的海绵组织厚度、叶片结构疏松度明显高于抗病品系;且苦瓜比叶重与其白粉病抗性关系不大。研究认为,苦瓜叶片蜡质含量、叶背面气孔及茸毛密度可以作为苦瓜白粉病抗性鉴定的参考指标。     

The cucurbit downy mildew pathogen Pseudoperonospora cubensis

Pseudoperonospora cubensis[(Berkeley & M. A. Curtis) Rostovzev], the causal agent of cucurbit downy mildew, is responsible for devastating losses worldwide of cucumber, cantaloupe, pumpkin, watermelon and squash. Although downy mildew has been a major issue in Europe since the mid-1980s, in the USA, downy mildew on cucumber has been successfully controlled for many years through host resistance. However, since the 2004 growing season, host resistance has been effective no longer and, as a result, the control of downy mildew on cucurbits now requires an intensive fungicide programme. Chemical control is not always feasible because of the high costs associated with fungicides and their application. Moreover, the presence of pathogen populations resistant to commonly used fungicides limits the long-term viability of chemical control. This review summarizes the current knowledge of taxonomy, disease development, virulence, pathogenicity and control of Ps. cubensis. In addition, topics for future research that aim to develop both short- and long-term control measures of cucurbit downy mildew are discussed. TAXONOMY: Kingdom Straminipila; Phylum Oomycota; Class Oomycetes; Order Peronosporales; Family Peronosporaceae; Genus Pseudoperonospora; Species Pseudoperonospora cubensis. DISEASE SYMPTOMS: Angular chlorotic lesions bound by leaf veins on the foliage of cucumber. Symptoms vary on different cucurbit species and varieties, specifically in terms of lesion development, shape and size. Infection of cucurbits by Ps. cubensis impacts fruit yield and overall plant health. INFECTION PROCESS: Sporulation on the underside of leaves results in the production of sporangia that are dispersed by wind. On arrival on a susceptible host, sporangia germinate in free water on the leaf surface, producing biflagellate zoospores that swim to and encyst on stomata, where they form germ tubes. An appressorium is produced and forms a penetration hypha, which enters the leaf tissue through the stomata. Hyphae grow through the mesophyll and establish haustoria, specialized structures for the transfer of nutrients and signals between host and pathogen. CONTROL: Management of downy mildew in Europe requires the use of tolerant cucurbit cultivars in conjunction with fungicide applications. In the USA, an aggressive fungicide programme, with sprays every 5-7 days for cucumber and every 7-10 days for other cucurbits, has been necessary to control outbreaks and to prevent crop loss. USEFUL WEBSITES: http://www.daylab.plp.msu.edu/pseudoperonospora-cubensis/ (Day Laboratory website with research advances in downy mildew); http://veggies.msu.edu/ (Hausbeck Laboratory website with downy mildew news for growers); http://cdm.ipmpipe.org/ (Cucurbit downy mildew forecasting homepage); http://ipm.msu.edu/downymildew.htm (Downy mildew information for Michigan's vegetable growers).     

A beta-1,3 glucan sulfate induces resistance in grapevine against Plasmopara viticola through priming of defense responses, including HR-like cell death

Sulfated laminarin (PS3) has been shown previously to be an elicitor of plant defense reactions in tobacco and Arabidopsis and to induce protection against tobacco mosaic virus. Here, we have demonstrated the efficiency of PS3 in protecting a susceptible grapevine cultivar (Vitis vinifera cv. Marselan) against downy mildew (Plasmopara viticola) under glasshouse conditions. This induced resistance was associated with potentiated H2O2 production at the infection sites, upregulation of defense-related genes, callose and phenol depositions, and hypersensitive response-like cell death. Interestingly, similar responses were observed following P. viticola inoculation in a tolerant grapevine hybrid cultivar (Solaris). A pharmacological approach led us to conclude that both callose synthesis and jasmonic acid pathway contribute to PS3-induced resistance.     

Putative new plant viruses associated with Plasmopara viticola-infected grapevine samples

In this study, we analysed a total of 16 libraries from over 150 grapevine leaf and grape samples infected with Plasmopara viticola (downy mildew of grapevine) to characterise the virome associated to this oomycete. Samples were collected in five distinct regions in Italy and in four different regions in Spain, representative of different pedoclimatic conditions and different grapevine cultivars during 2018 growing season. Due to the metagenomics nature of the samples (containing at least both downy mildew hyphae and spores, and grapevine cells residues), we were able to assemble several plant viruses and a few possible novel plant virus genomes with our in silico analysis. We detected several plant virus variants already reported in grapevine, and a putative new ilarvirus previously unreported in grapevine. Furthermore, we characterised three new phenui-like viruses (in the order Bunyavirales), one of which shares some commonalities with plant coguviruses. Finally, we report a new strict association of three viral segments (one flavi-like and two virga-like) that we propose to be a new virus taxon named jivivirus.