RLP AgroScience (Germany)

Abstract Grape downy mildew, caused by the oomycete Plasmopara viticola, is a major threat to Vitis vinifera grape production. Several breeding programs rely on resistance factors (Rpvs) from American and Asian Vitis species to confer resistance to P. viticola. Although the use of these crossing hybrids offers a promising strategy for disease control, variants capable of overcoming host resistance are emerging. A thorough characterization of these isolates is needed to define new strategies for breeding programs. The investigation of varying aggressiveness of two P. viticola pathotypes was investigated. One pathotype is unable to overcome Rpv3.1 based resistance and another pathotype was isolated from a grapevine carrying the Rpv3.1 locus. Their aggressiveness was evaluated on five grapevine genotypes harboring distinct combinations of Rpv loci. Macroscopic and microscopic development of the pathogen was characterised throughout its colonization of grapevine leaves. Our findings demonstrate that the P. viticola isolate NW-10/16 is not only capable of overcoming Rpv3-based resistance but also exhibited a faster growth, increased sporulation, and a denser mycelial colonization within the plant mesophyll when compared with the avRpv3 + isolate in susceptible plants. The identification and characterization of new, more aggressive, P. viticola pathotypes is crucial to promote durable management of the resistant grapevine hybrids and to mitigate the threat of downy mildew.

The foliar wash-off coefficient is a parameter used by environmental fate models to estimate the amount of chemical removed from leaf surfaces by rainfall. In the European Union it is used by FOCUS surface water models to estimate soil loadings following rainfall after leaf surfaces have been treated with plant protection products. Currently, a default value of 0.5/cm is assumed for this parameter, although there is provision to provide experimental data to replace this default. The European Food Safety Authority proposed to increase the default parameter value to 1.0/cm. This increases the need for experimental refinement studies. However, no guidance for a harmonized protocol exists to estimate this parameter. We describe the results of a ring-test conducted to start a process of developing a harmonized experimental protocol to measure the foliar wash-off parameters, conducted by several laboratories across Europe. The proposed design uses whole plants (rather than individual leaves) to retain as much realism as possible. The extent of wash-off is then determined by comparison of compound residues in two sets of plants (with and without a defined rainfall event) measured using a fully validated crop residue method. This initial ring test used tebuconazole (Folicur EW 250) sprayed at 100 g ai/ha onto tomato plants at BBCH25. Each laboratory measured the residues before and after a rainfall event of 20 mm/h for 1 h and calculated the percentage of wash-off from these data. There was good agreement across the eight participating laboratories with a mean percentage of wash-off of 66.8% and a 95% confidence interval of ±11.8%. Determination of robust wash-off parameters was therefore considered feasible using the proposed test design. Environ Toxicol Chem 2023;42:535-541. © 2022 SETAC.

In Europe, the risk assessment for bees at the European Union or national level has always focussed on potential impacts on honeybees. During the revision of the European Food Safety Authority bee guidance it was explicitly stated that bumblebees and solitary bees should be considered as well and consequently concerns were raised regarding the representativeness of honeybees for these other bee species. These concerns originate from differences in size as well as differences in behavioral and life history traits of other bee species. In response to this concern, the non-Apis working group of the International Commission for Plant-Pollinator Relationships initiated a ring-test of a semifield tunnel study design using the bumblebee Bombus terrestris. Nine laboratories participated, validating and improving the proposed design over a 2-year period. The intention of the ring-test experiments was to develop and if possible, establish a test protocol to conduct more standardized semifield tests with bumblebees. In the present study, the results of the ring-tests are summarized and discussed to give recommendations for a promising experimental design. Environ Toxicol Chem 2022;41:2548-2564. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

<p>Surface runoff from agricultural fields is a major input pathway of pesticides into surface waters. The aim of this project was to i) analyze the effectiveness of various mitigation measures to reduce pesticide runoff and erosion inputs into surface waters, ii) assess the suitability of the measures found effective for use in the quantitative environmental exposure assessment for authorization of plant protection products (PPP), and iii) make recommendations how the potentially suitable measures could be applied in risk assessment of PPP in Germany. Following a literature analysis, 16 risk mitigation measures were presented to five experts for evaluation of effectiveness, cost-effectiveness, controllability, current distribution and dissemination potential. Measures finally selected for quantitative analysis belong to 3 groups: vegetative filter strips (VFS), soil conservation measures and micro-dams in row crops. Subsequently, the effectiveness of the recommended measures was evaluated based on experimental data using different statistical methods (e.g. CART, MLR, graphical methods).</p><p>The quantitative analysis confirmed the effectiveness of VFS and micro-dams. For soil conservation measures (especially mulch-till), the evaluated data showed highly variable results. This was partly caused by the heterogeneity of the experimental data, which also made it difficult to aggregate the results of different studies.</p><p>The following conclusions were drawn: Both VFS and micro-dams can be recommended for application in quantitative environmental exposure assessment for pesticides.  However, infiltration and sedimentation in VFS should be simulated with a mechanistic model such as VFSMOD. The effect of micro-dams can be modelled as a reduction of the runoff Curve Number (CN). The runoff modelling should be carried out with a model such as PRZM which adjusts the CN daily based on soil water content.</p>

SUMMARYIn plants, small interfering RNAs (siRNAs) are a quintessential class of RNA interference (RNAi)-inducing molecules produced by the endonucleolytic cleavage of double stranded RNAs (dsRNAs). In order to ensure robust RNAi, siRNAs are amplified through a positive feedback mechanism called transitivity. Transitivity relies on RNA-DIRECTED-RNA POLYMERASE 6 (RDR6)-mediated dsRNA synthesis using siRNA-targeted RNA. The newly synthesized dsRNA is subsequently cleaved into secondary siRNAs by DICER-LIKE (DCL) endonucleases. Just like primary siRNAs, secondary siRNAs are also loaded into ARGONAUTE proteins (AGOs) to form an RNA-induced silencing complex (RISC) reinforcing the cleavage of the target RNA. Although the molecular players underlying transitivity are well established, the mode of action of transitivity remains elusive. In this study, we investigated the influence of primary target sites on transgene silencing and transitivity using the GFP-expressingNicotiana benthamiana16C line, high pressure spraying protocol (HPSP), and synthetic 22-nucleotide (nt) long siRNAs. We found that the 22-nt siRNA targeting the 3’ of the GFP transgene was less efficient in inducing silencing when compared to the siRNAs targeting the 5’ and middle region of the GFP. Moreover, sRNA sequencing of locally silenced leaves showed that the amount but not the profile of secondary RNAs is shaped by the occupancy of the primary siRNA triggers on the target RNA. Our findings suggest that RDR6-mediated dsRNA synthesis is not primed by primary siRNAs and that dsRNA synthesis appears to be generally initiated at the 3’ end of the target RNA.SIGNIFICANCE STATEMENTThis work answers a long-standing question about the role of siRNA triggers in initiating transitive silencing. By using high-pressure spraying-mediated delivery of synthetic siRNAs, we provided experimental evidence that target position of 22-nt-long primary siRNAs influences the efficiency of RDR6-driven double stranded RNA (dsRNA) synthesis, but it does not change the profile of accumulating secondary siRNAs originating from processing of RDR6-produced dsRNA.

RESUMEN Este artículo aborda la ocupación como un aspecto central de la experiencia humana; aduce que la ocupación satisface necesidades humanas básicas que son esenciales para la supervivencia, proporcionando los mecanismos para que las personas ejerciten y desarrollen capacidades innatas de carácter biológico, social y cultural para adaptarse a los cambios ambientales y para prosperar como individuos. Sin embargo, las necesidades ocupacionales básicas de las personas han quedado cubiertas tras la complejidad actual de la tecnología y la economía ocupacional, y por las restricciones, divisiones y valores sociales establecidos progresivamente a lo largo del tiempo.

Grapevine, one of the most important fruit crops worldwide is host to various pathogens, some of which have been spread intercontinentally in the early history of viticulture. One of the most problematic diseases is downy mildew, caused by the oomycete Plasmopara viticola (Berk. & Curt.) Berl. & de Toni which was introduced to Europe from North America in the 19th century. In addition to the establishment of chemical plant protection measures, extensive resistance breeding activities have succeeded in establishing varieties that are able to limit the propagation of this pathogen Recent studies have indicated an important role of subtilisin-like serine proteases (subtilases) in association with this increased disease tolerance. Gene expression analysis of two candidate subtilases was performed in seven cultivars with different levels of susceptibility to P. viticola. Two P. viticola isolates with different degrees of virulence were tested. Our results show that subtilases display different patterns of expression: Cucumisin exhibits peaks of expression, while VviSBT5.3a presents a bimodal behaviour. Nevertheless, both subtilases have a more pronounced response to the more virulent P. viticola isolate, which supports the hypothesis that the two subtilases are involved in the early events of the defense mechanisms.

The RISKMIN Model was a research project funded by the German Federal Office of Consumer Protection and Food Safety between 2012 and 2016 to support the development of a landscape-based mitigation approach for assessing different measures and their effects on agrobiodiversity. Conducted by an interdisciplinary cooperation between different research groups in Germany two representative landscapes were chosen as pilot regions. Based on a very high-resolution landscape analysis and a comprehensive survey of the terrestrial agrobiodiversity in these regions a simulation of different risk mitigation measures was realized by reference to potential scenarios. The resulting effects could be analysed, quantified and visualized with the help of geographic information systems (GIS). Main results are that the most effective measure on landscape level is the extensification of the land use, but on the other hand, that the combination of in crop and off crop measures does have the most effects for the landscape elements with the highest ecological values.

A nationwide monitoring with regard to the presence and distribution of ‘Candidatus Phytoplasma prunorum’ and its vector, Cacopsylla pruni, has been carried out in Germany between 2013 and 2017. In total, 286 sites with cultivated and wild Prunus species were surveyed. 806 plant samples covering 94 administrative districts in all 13 federal area states and one city-state were analysed by PCR. Furthermore, 3108 C. pruni were caught in 63 districts and tested for ‘Ca. P. prunorum’. European stone fruit yellows was found mainly in symptomatic apricot, plum, almond and peach but also for the first time in Germany in sweet cherry. Non-symptomatic infections were detected in 437 randomly sampled P. spinosa at 104 sites without any stone fruit growing nearby representing a natural infection rate of 14%. The vector C. pruni was found on all P. spinosa plants at 62 sites spread across Germany. The infection rate of C. pruni was 1–2% regardless whether the insects were caught in stone fruit growing areas or at wild habitats. Our results strongly indicate that ‘Ca. P. prunorum’ is widespread in all natural habitats in Germany and that wild P. spinosa represent a major source of infection in stone fruit orchards. A representative sample of 1164 individuals of C. pruni captured at 100 sites was molecularly typed: all but one insect were of B-type, the one which is the proven vector of ‘Ca. P. prunorum’. C. pruni A-type was detected for the first time in Germany near the French border.