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The high susceptibility of European grapevine cultivars to downy mildew (DM) and powdery mildew (PM) causes the intensive use of fungicides. Fungus-resistant cultivars (FRCs) with different resistance (R) loci have been bred and could play an important role in reducing plant protection treatments (PPTs). However, little information is available about the extent to which PPTs can be reduced in the field through the use of FRCs and the associated economic advantages. In this study, different strategies with reduced PPTs on FRCs were tested in field experiments. The results demonstrated that the number of PPTs can be reduced by 60 to 90%, resulting in reductions in applied copper and sulfur by 52 to 79% through the use of FRCs compared with susceptible cultivars, without affecting grape or plant health. The saving potential varied among years, depending on the type of R loci and climatic conditions. Furthermore, this study highlights that completely omitting PPTs in the cultivation of FRCs can result in PM or DM infections and possible loss of yield and fruit quality. In addition to the field experiments, a two-year observation of the performance of FRCs in commercial vineyards was undertaken, which highlighted not only the significant reduction in PPTs but also the financial savings that can be achieved through the use of FRCs. [ABSTRACT FROM AUTHOR]

BACKGROUND: Copper‐containing fungicides are applied broadly in organic viticulture against downy mildew caused by Plasmopara viticola. Although long‐term application of copper‐based fungicides is associated with ecotoxic effects on the environment, their use in viticulture is required until sustainable alternatives are available. Trichoderma spp. might be a promising approach to fungicide reduction while promoting plant growth and development and displaying biocontrol activity. This study aims to examine the tolerance and compatibility of Trichoderma spp. to copper fungicides. This work contributes to the development of a spray application consisting of a copper‐tolerant Trichoderma sp. combined with a downscaled copper fungicide rate against P. viticola. RESULTS: Trichoderma spp. isolated from grapevine wood in vineyards were identified and used for tolerance screening in various concentrations of copper fungicides. Copper hydroxide was identified as being highly compatible with Trichoderma. Two Trichoderma candidates, T. koningiopsis and T. harzianum, showed high copper tolerance in mycelial growth and germination tests, and were adapted to 2.85 g Cu L−1 of the selected fungicide. Microscopic investigations showed the attachment of copper compounds to fungal cell walls and copper uptake within the cytoplasm. In the case of high tolerance, large‐scale copper uptake was prevented. CONCLUSION: Our findings identified two highly copper‐tolerant Trichoderma isolates with natural adaptation to the vineyard ecosystem, which could be further tested as biostimulants and biocontrol agents, combined with a reduced fungicide rate for sustainable plant protection. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

European grapevine cultivars (Vitis vinifera spp.) are highly susceptible to the downy mildew pathogen Plasmopara viticola. To reduce the dependence of viticulture on chemical inputs, and thereby reduce the ecological and economic burden of wine production, a number of breeding programs have introgressed resistance loci from wild North American and Asian Vitis species into V. vinifera resulting in new fungus-resistant grapevine cultivars (FRCs). These FRCs are a promising strategy to reduce the impact of disease management. Due to variety-specific resistance differences, little is known about the required amount and the potential reduction of fungicide applications. The aim of the project was to investigate the degree of resistance of new FRCs and thus the capability of fungicide reduction in the vineyard over a 6 year time period. For this purpose, the infection and sporulation ability as well as the development of P. viticola in different FRCs and susceptible cultivars were investigated and compared. Additionally, FRCs with reduced plant protection treatments were compared to traditional cultivars. On the basis of the results obtained, adjusted plant protection recommendations for FRCs were developed. The on-farm experiments showed that the use of FRCs in combination with reduced plant protection management strategies offers the possibilities to significantly reduce the number of fungicide treatments required for grape production. Results obtained from this study demonstrated that the deployment of FRCs can save 50-85 % of fungicide applications in viticulture depending on the degree of the vairiety's resistance level. The omission of all plant protection applications can ultimately lead to negative effects on yield, quality and even resistance durability. The latter was demonstrated by the identification of new P. viticola isolates capable of overcoming Rpv3- and Rpv12-mediated resistance. Therefore, this study demonstrates the importance of sustainable breeding and crop protection strategies. [ABSTRACT FROM AUTHOR]

The high susceptibility of European grapevine varieties (Vitis vinifera) to downy mildew (Plasmopara viticola) leads to intensive use of fungicides in viticulture. To reduce the use of fungicides, resistance loci from wild Vitis species have been crossed into Vitis vinifera varieties. The resulting new fungusresistant grapevine cultivars (FRCs) represent an important tool for reducing pesticide applications in viticulture. Due to variety-specific resistance differences, little is known about the type and timing of the plant defense responses mediated by different resistance loci. Since the long-term goal of resistance breeding is to pyramidize several resistance loci, these should be based on different resistance mechanisms to increase the durability of the resistance. Therefore, detailed knowledge of the different defense mechanisms and resistance genes conferred by the respective Rpv-loci is essential to ensure sustainable resistance management and durable as well as stable resistance breeding. Therefore, the resistance mechanisms mediated by the Rpv10-, Rpv3-and/or Rpv12-loci on downy mildew development, sporulation ability, onset of programmed cell death (PCD), production of hydrogen peroxide and stilbene levels were evaluated and compared. Furthermore, resistancebreaking isolates were used as a tool to additionally evaluate whether the resistance loci are based on different mechanisms. In order to understand the mechanistic basis of the defense responses mediated by the Rpv12-locus, cultivars containing this locus were examined in more detail. The experiments revealed an early and locally precise defense response in Rpv10-, Rpv12- and Rpv12/Rpv3-genotypes, whereas a delayed defense response in Rpv3-genotypes was observed. These temporal differences correlated with an increase in the trans-resveratrol level and the formation of hydrogen peroxide shortly before onset of PCD. The differences in timing of onset of Rpv-loci specific defense reactions following downy mildew infection could be responsible for the observed differences in hyphal growth, sporulation and cultivar-specific susceptibility to this pathogen in the vineyard. Regarding the Rpv12-locus described first by Venuti et al. 2013, we were able to further narrow down the region, which confers resistance by new resistance markers. In this reduced region 10 putative disease resistance R-genes were found and are analyzed bioinformatically. [ABSTRACT FROM AUTHOR]