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Grapevine Pinot gris virus (GPGV) isolates were obtained from German vineyards to investigate their diversity. Phylogenetic and dating analyses of these and GPGV genes and genomes available in GenBank showed that the virus probably diverged from grapevine berry inner necrosis virus (GINV) in wild and cultivated Vitis species, notably Vitis coignetiae, growing in North‐east Asia around 3500 years ago. GPGV probably infected the Eurasian grape (Vitis vinifera subsp. vinifera) when those cultivars were first taken to China during the Han Dynasty (226 BCE–220 CE). GPGV then spread to Europe around 1800 CE, probably via the dissemination of infected plants, and from there, eventually spread worldwide. German isolates were only found in all parts of the post‐1800 CE phylogeny. The German isolates were genetically more diverse, for both MP and CP genes, than those of other European populations, suggesting that the initial stages of the GPGV invasion of Europe were in Germany, not Italy. We discuss the likely North‐east Asian origin of both GPGV and GINV, and the possible coincidences of phylogenetic date estimates with changes to European and world viticulture practices. [ABSTRACT FROM AUTHOR]

Introduction Mango (Mangifera indica) cultivars occur in two ecotypes that are characterized by embryony: (i) polyembryonic tropical ecotypes (South-East Asian origin) and (ii) monoembryonic subtropical ecotypes (Indian origin) (Litz 2009). [...], Within a polyembryonic mango seedling tree population, the genetic background of individuals should be identical because vigorous plants for cultivation are expected to develop from nucellar embryos representing maternal clones. Due to the fact that the mango cultivar 'Hoi' is assigned to the polyembryonic ecotype, an intra-cultivar variability of ethylene receptor genes was unexpected. Ethylene receptors in plants are conserved, but the number of receptors or receptor isoforms is variable regarding different plant species. However, it is shown here that the ethylene receptor MiETR1 is present in various isoforms within the mango cultivar 'Hoi'. The investigation of single nucleotide polymorphisms revealed that different MiETR1 isoforms can not be discriminated simply by individual single nucleotide exchanges but by the specific arrangement of single nucleotide polymorphisms at certain positions in the exons of MiETR1. Furthermore, an MiETR1 isoform devoid of introns in the genomic sequence was identified. The investigation demonstrates some limitations of high resolution melting and ScreenClust analysis and points out the necessity of sequencing to identify individual isoforms and to determine the variability within the tree population. Key words: ethylene receptor ETR1, high resolution melting, intra-cultivar sequence variability, Mangifera indica, ScreenClust. Au sein d'une population de plantules de manguier a embryons multiples, le fond genetique des individus devrait s'averer identique car les plants vigoureux destines a la culture seront issus d'embryons nucellaires constituant des clones maternels. Comme le cultivar de manguier <> appartient a l'ecotype caracterise par des embryons multiples, une variabilite intra-cultivar pour les genes codant pour des recepteurs de l'ethylene etait inattendue. Chez les plantes, les recepteurs de l'ethylene sont conserves, mais le nombre de recepteurs ou de leurs isoformes varie entre especes. Les auteurs montrent ici que le recepteur de l'ethylene MiETR1 presente differents isoformes au sein du manguier <>. L'etude des polymorphismes mononucleotidiques a revele qu'il n'est pas possible de distinguer les differents isoformes de MiETR1 sur la base de simples echanges de polymorphismes individuels. Pour y arriver, il fallait examiner l'arrangement specifique de polymorphismes mononucleotidiques a certaines positions au sein des exons de MiETR1. De plus, un isoforme de MiETR1 depourvu d'introns au sein de la sequence genomique a ete identifie. Cette investigation demontre certaines limitations aux analyses de denaturation a haute resolution (<>) et ScreenClust. Cela souligne la necessite du sequencage pour l'identification des isoformes individuels et la determination de la variabilite au sein d'une population d'arbres. [Traduit par la Redaction] Mots-cles: recepteur de l'ethylene ETR1, denaturation a haute resolution, variation nucleotidique intra-varietale, Mangifera indica, ScreenClust.

When monitoring leafhoppers for phytoplasma vector management in the grapevine growing regions of Rhineland- Palatinate, Germany, some individuals of Hishimonus hamatus were collected at Neustadt a. d. Weinstraße. Specimen were caught by net as well as with Yellow Sticky Traps placed in shrubs. The species was determined visually and verified by molecular analysis. This is the first record of H. hamatus in Germany and also north of the Alp mountains denoting that this species is further expanding its territory in Europe. [ABSTRACT FROM AUTHOR]

Grapevine is a perennial crop, which is cultivated intensively over many decades. This provides optimal conditions for viroids, which need several months or years to be fully established in their host. After the viroids are initially introduced through infected planting material, they are easily transmitted through crop management practices. Since most viroids do not lead to strong regular symptoms in grapes, they are considered to be latent, thus unimportant for the grape producer. This might be the reason, why viroids can be found in most, if not all, grape production areas worldwide. Currently, there are six viroids reported to infect grapevines, of which the Australien grapevine viroid is thought to have evolved through recombination of different viroids present in a single host. Studies in the 1980s showed that the hop stunt viroid (HSVd) is present in Germany. However, other viroids are also present and known to induce yellow spots especially under warm weather conditions like the grapevine yellow speckle viroid 1 (GYSVd-1). Because grapevine is a reservoir for hoppathogenic viorids like the HSVd and also global warming is likely to increase symptom severity of GYSVd-1 in the future a preliminary survey and subsequent comparative sequence analysis was conducted to get an up-to-date overview of the infection status of German grapes. The analysis of leaf samples of commercial grape cultivars with reverse transcription and subsequent PCRs show that HSVd and GYSVd-1 are widely distributed in Germany. Furthermore, Sanger sequencing revealed that the dominat HSVd-variant (similar to X06873) is different from variants typically found in other grapes, citrus or hops. The effect of this HSVd-variant as pathogene for hop has not yet been studied. The effect of the "latent" infection of HSVd and GYSVd for grape yield and subsequent wine quality has not yet been determined. These topics need to be addressed in further studies. [ABSTRACT FROM AUTHOR]

Rootstock breeding focuses on nematode resistance to fight indirectly the fanleaf degeneration disease caused by Grapevine fanleaf virus (GFLV), which is transmitted by the vector nematode Xiphinema index. Screening of candidate Vitis genotypes was performed based on nematode reproduction and fertility rates and virus diagnosis of test plants after inoculation with viruliferous nematodes and incubation for 35 days in glass vials. 11 Vitis candidates out of 68 genotypes were identified as nematode resistant and 3 of them remained GFLV-negative after exposure to viruliferous nematodes in the assay. The time and space saving setup of the assay enabled the efficient identification of promising nematode resistant genotypes with a genetic background from Vitis aestivalis or Vitis labrusca. The selected candidate genotypes may be considered for future rootstock resistance breeding. [ABSTRACT FROM AUTHOR]

Climate change has a significant impact on viticulture. Particular phenological growth stages such as flowering and berry development, the challenge of certain grape varieties to adapt to higher temperatures and drought stress, as well as the occurrence of undesirable off-flavours in wine represent a wide range of impairments. The growing conditions of many autochthonous varieties become poorer as they are adapted to cooler climate due to the longstanding selection process. In addition, sunburn damages to grapes have frequently occurred in Germany since the 1990s, which is associated with an increase of global radiation exposures as well. In 'Riesling' wines, sensory impairments known as "petrol off-flavour" have also occurred in this context in recent years. According to previous studies, the causes of this off-flavour are attributed to rising temperatures and an overall increase in radiation exposure whereby carotenoids in grape berries are degraded into C13 norisoprenoids. Further chemical reactions ultimately result in the compound 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) which gives a dull and petrol-like odour as well as a bitter and astringent taste to the wines. Therefore, sunburn damages significantly reduce both, yield quantity and wine quality. One research objective of the project is to develop a prevention strategy in which optimized canopy management in combination with application of various compounds or shading reduces sunburn susceptibility of 'Riesling' grapes. First results suggest an early defoliation of the bunch zone and application of china clay or lime to significantly decrease the risk of sunburn. Alternatively, different nets could improve grape health. Sunburn avoidance needs to be as effective, economically affordable and sustainable as possible, but also without impairing wine quality. Moreover, grape varietal differences in sunburn susceptibility could be observed. The fungusresistant grape variety 'Calardis Blanc' visually showed a significantly higher tolerance compared to the genetically distantly related 'Riesling'. To get further insights regarding sunburn tolerance, experiments in the field as well as in the climate chamber are conducted. Berry skins are investigated on a transcriptional and metabolic level to identify the underlying molecular mechanisms and evaluate their temporal regulation. For this purpose, a deeper understanding of the sunburninducing factors is essential as well. [ABSTRACT FROM AUTHOR]

Hot water treatment (HWT) applied on dormant woody plant material to control Grapevine Trunk Diseases (GTD) showed variable results in previous studies. In this project, a field experiment was carried out to investigate the effect of HWT on GTD pathogens (Phaeomoniella chlamydospore (Pch), Phaeoacremonium minimum (Pmi), Botryosphaeriaceae (BOT) species). Inoculated wood cuttings were treated in a hot water tank under practical conditions, grafted onto healthy rootstocks and planted in nurseries. Pathogen development was analysed in wood samples at distinct time points after treatment. Pch and BOT could be successfully eliminated through HWT. However, only a reduced infection by Pmi was observed in the treated samples. To determine the influence of HWT on the growth of Trichoderma and its long-term antagonistic effect following HWT on GTD pathogens, a commercially available biocontrol agent product, Vintec®, [Trichoderma atroviride strain SC1 (TASC1), Belchim Crop Protection Deutschland GmbH] was tested. No negative impact of HWT could be detected on the growth of TASC1, and thus its antagonistic ability against the GTD pathogens was also not affected. Heat tolerance of the distinct developmental stages of each GTD pathogens was assessed at different temperature-time combinations under laboratory conditions. In general, Pch and BOT were more sensitive to HWT than Pmi at both tested developmental stages. Pmi showed reduced sensitivity to HWT at the ungerminated spore stage. Conidial germination was not inhibited following an incubation of the spore suspension for 45 minutes at 50°C, whereas no survival of treated mycelia of Pmi could be detected. These results suggest that HWT can be a useful tool to reduce infections with GTD pathogens in propagation material without affecting the antagonistic effects of TASC1. [ABSTRACT FROM AUTHOR]

In grapevine, the defense regulator ENHANCED DISEASE SUSCEPTIBILITY (EDS) is present as a multimember gene family and plays a role in basal defense in plants. EDS1 is highly conserved and functional in both, Vitis vinifera cv. 'Cabernet Sauvignon' and Vitis aestivalis cv. 'Norton'; hence, the regulation of EDS1 - regarding tissue specificity and transcript level - may be a key for powdery mildew (PM) resistance in cv. 'Norton', while cv. 'Cabernet Sauvignon' is susceptible. Besides PM resistance, also salicylic acid (SA) signaling and the degree of accumulation in leaves is thought to be associated with EDS1 expression. By preliminary analysis the SA content was determined in leaves of several resistant and susceptible accessions from both species, V. vinifera and V. aestivalis, which corroborates a tendency that SA accumulation and PM resistance may be linked. Further, the putative promoter sequences of the EDS1 genes (pEDS1) from cv. 'Cabernet Sauvignon' and cv. 'Norton' were bioinformatically analyzed with the Genomatix software suite to predict transcription factor binding sites (TFBS) and higher order regulatory models. The analysis revealed that the promoter sequences contain some conserved but also highly variable regions as well as a different set of TFBS and regulatory models. In pEDS1 from cv. 'Cabernet Sauvignon' higher order models containing AHBP, DOFF, L1BX, MYBL, OPAQ and WRKY motifs are predicted. In contrast, in pEDS1 from cv. 'Norton' other putative models are present containing OPAQ and DOFF motifs only. The variations within the regulatory regions of pEDS1 are presumably responsible for specific EDS1 expression and associated SA signaling. [ABSTRACT FROM AUTHOR]

Vitis vinifera (grapevine) is the most economically important deciduous fruit crop, but cultivated grapevine varieties lack adequate innate immunity to a range of devastating diseases. To identify genetic resources for grapevine innate immunity and understand pathogen defense pathways in a woody perennial plant, we focus in this study on orthologs of the central Arabidopsis thaliana defense regulator ENHANCED DISEASE SUSCEPTIBILITY1 ( EDS1). The family of EDS1-like genes is expanded in grapevine, and members of this family were previously found to be constitutively upregulated in the resistant variety ‘Norton’ of the North American grapevine species Vitis aestivalis, while they were induced by Erysiphe necator, the causal agent of grapevine powdery mildew (PM), in the susceptible V. vinifera variety ‘Cabernet Sauvignon’. Here, we determine the responsiveness of individual EDS1-like genes in grapevine to PM and salicylic acid, and find that EDS1-like paralogs are differentially regulated in ‘Cabernet Sauvignon’, while two are constitutively upregulated in ‘Norton’. Sequencing of VvEDS1 and VaEDS1 cDNA and genomic clones revealed high conservation in the protein-encoding sequence and some divergence of the promoter sequence in the two grapevine varieties. Complementation of the Arabidopsis eds1- 1 mutant showed that the EDS1-like gene with highest predicted amino acid sequence similarity to AtEDS1 from either grapevine varieties is a functional ortholog of AtEDS1. Together, our analyses show that differential susceptibility to PM is correlated with differences in EDS1 expression, not differences in EDS1 function, between resistant ‘Norton’ and susceptible ‘Cabernet Sauvignon’. [ABSTRACT FROM AUTHOR]

The ectoparasitic nematode Xiphinema index transmits grapevine fanleaf virus (GFLV) during feeding on grapevine roots, causing fanleaf degeneration in the plant. Hence, resistance breeding is a key to develop novel rootstocks to overcome such threats. In past years, various grapevine species were screened, and a few candidates with partial resistance were identified. However, they were hardly sufficient for viticulture because of their many agronomical defects. To develop reliably resistant rootstocks applicable in viticulture, multiple Vitis spp. genotypes were analyzed using root inoculation with nematodes in glass vials as an early and easy evaluation test. Resistance levels were evaluated 35 days after inoculation based on nematode reproduction factors, focusing on juveniles and eggs. Infection of grapevines with GFLV was analyzed after inoculation with viruliferous X. index . With this fast screening system, putative candidates with resistances against X. index have been identified for future breeding programs. Particularly, genotypes with the genetic background of Vitis aestivalis and Vitis labrusca were found to be nematode-resistant.

Flavescence dorée (FD) and Bois noir (BN) are the principal grapevine yellows diseases in Europe caused by distinct phytoplasmas: FD by 16SrV phytoplasmas (FDp), BN by Candidatus Phytoplasma solani. FDp is spread epidemically by the introduced Nearctic Deltocephalinae Scaphoideus titanus and is listed as a quarantine pest in the European Union (Regulation (EU) 2019/2072). Black Alder (Alnus glutinosa) is a common asymptotic host of 16SrV phytoplasmas in Europe and considered the original host of FDp (Malembic-Maher et al. 2020). Palatinate grapevine yellows (PGY) transmitted from alder to grapevine by the Macropsinae Oncopsis alni (Maixner et al. 2000) is not transmissible by S. titanus, unlike isolates transmitted by the autochthonous Deltocephalinae Allygus spp. and the invasive Orientus ishidae (Malembic-Maher et al. 2020). Germany is considered free from FD in grapevine and from its vector. A single case in a nursery in 2014 was eradicated (EPPO 2017). Since S. titanus was detected in 2016 in the neighboring French Region of Alsace, monitoring of FD was carried out in Germany. It was focused on vineyards within a distance of 100 m from stands of alder trees. A geodata-based risk map (Jalke 2020) was used to identify those plots. All symptomatic vines sampled until September 2020 proved to be infected by BN or, occasionally, by PGY. Eight vines with typical symptoms were sampled in vineyards adjacent to alder stands in the winegrowing region of Rheinhessen in September 2020. Symptoms comprised leaf rolling and discoloration, incomplete lignification, black pustules on shoots, dried inflorescences and shriveled berries. Diseased shoots were black and necrotic in December. Leaf midribs were sampled for total DNA extraction. The phytoplasma 16S rRNA gene was amplified by generic primers R16F2/R2-mod followed by a nested PCR using 16Sr(V) group-specific primers R16(V)F1/R1, and primers R16(I)F1/R1 (Lee et al. 1995) to detect 'Candidatus Phytoplasma solani', associated with BN. While BN was detected in seven vines, one sample tested positive for 16SrV phytoplasma. This result was confirmed by triplex real-time Taq-Man assay based on rpl14 gene sequences (IPADLAB), by multiplex real-time PCR of map locus as well as by Loop-mediated isothermal amplification (LAMP) according to the EPPO diagnostic standard PM 7/079(2) (EPPO 2016). PCR-products of the map- and the vmpA-Gene (Malembic-Maher et al., 2020) were sequenced and compared to reference sequences to distinguish between FD- and non-FD genotypes. The isolate from the diseased vine exhibited 100% identity with map-M38 (Accession No. LT221933), a genotype of the map-FD2 cluster. The same genotype was detected in A. glutinosa and Allygus spp. sampled at the infested site. A 234 bp sequence of the first repeat of the vmpA-gene showed 100% identity with the S. titanus transmitted isolate FD-92 (Accession No. LN680870) of the vmpA-II cluster. It can be concluded, that the 16SrV-isolate detected in a symptomatic grapevine is infected by FD and not PGY. This is the first report of FD in a vineyard in Germany. The infected vine of cv. Silvaner was 25 years old. While infected planting material is an unlikely source of the infection, a transmission of FDp from alder is highly probable. Finding a single FD-infection after several years of testing implies a low risk originating from the wild compartment, but the approach of the vector S. titanus justifies further monitoring activities. The infected vine was eradicated.