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Background
Climate change will increase the occurrence of plants being simultaneously subjected to drought and pathogen stress. Although it is well known that drought can alter the way in which plants respond to pathogens, knowledge about the effect of concurrent drought and biotic stress on grapevine is scarce. This is especially true for Plasmopara viticola, the causal agent of grapevine downy mildew. This research addresses how vines with different drought tolerances respond to challenge with P. viticola, drought stress or their combination and how one stress affects the other.
Results
Artificial inoculation was performed on two cultivars exposed to full or deficit irrigation in the Mediterranean climate of Cyprus. In parallel, leaf discs from these plants were inoculated under controlled conditions. Leaves were sampled at an early infection stage to determine the influence of the single and combined stresses on oxidative parameters, chlorophyll, and phytohormones. Under irrigation, the local Cypriot cultivar Xynisteri was more susceptible to P. viticola than the drought-sensitive cultivar Chardonnay. Successful infection by P. viticola at 1.5 days post inoculation was associated with high levels of indole-3-acetic acid (IAA), salicylic acid (SA), jasmonic acid (JA), and proline and strong decreases in antioxidant enzyme activity. Drought, on the other hand, triggered the accumulation of IAA and abscisic acid (ABA), which antagonized JA and SA. Exposure to drought stress increased the susceptibility to P. viticola of the leaves inoculated under controlled conditions. Conversely, both cultivars showed resistance against P. viticola when inoculated in planta under continued deficit irrigation. Despite their resistance, the pathogen-associated responses of IAA, antioxidant enzyme activity, and proline still occurred in these drought-stressed plants. Surprisingly, ABA, rather than the generally implicated JA and SA, seemed to play a prominent role in this resistance.
Conclusions
Drought exposure increased the susceptibility of leaves inoculated in vitro. Conversely, deficit irrigation induced resistance to P. viticola in both Chardonnay and Xynisteri plants inoculated in planta. ABA, rather than JA and SA, was implicated in this resistance. The irrigation-dependent susceptibility indicates that the changing climate and the practices used to mitigate its effects may have a profound impact on plant pathogens.
Keywords
Climate change, irrigation, drought stress, biotic stress, grapevine, downy mildew, Plasmopara viticola, phytohormones, oxidative stress, abscisic acid
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This is a list of supplementary files associated with this preprint. Click to download.
- Additionalfile1.xlsx
Additional file 1 (.xls): Table S1 P-values for the different factors and interactions retained in the models after model selection. Interaction terms that were not important for the models were removed based on the AIC. The linear regression analyses the interactions between the predictor variables: cultivar (Chardonnay or Xynisteri), irrigation (full or deficit), duration (of the irrigation treatment; 9 or 16 dot), and pathogen (P. viticola or water inoculation). Highlighted cells have p-value < 5% (dark green); 5%< p-value <10% (light green); 10%<p-value<15% (grey).
- Additionalfile2.xlsx
Additional file 2 (.xls): Table S2 Coefficient estimates for the different factors and interactions retained in the models after model selection. Interaction terms that were not important for the models were removed based on the AIC. The linear regression analyses the interactions between the predictor variables: cultivar (Chardonnay or Xynisteri), irrigation (full or deficit), duration (of the irrigation treatment; 9 or 16 dot), and pathogen (P. viticola or water inoculation). Coefficients with a p-value < 15% are highlighted, in a darker shade if the p-value<5%. The colours indicate a positive (blue) or negative (red) correlation.
- Additionalfile3.tiff
Additional file 3 (.tif): Fig. S1 Relative humidity (RH) and temperature during the experiment. The data were recorded every 20 minutes with an on-site data logger in sheltered conditions.
- Additionalfile4.tiff
Additional file 4 (.tif): Fig. S2 Volumetric water content (VWC) of the soil during the experiment. Deficit irrigation (DI) was maintained at 40% of the full irrigation (FI) based on the volumetric pot soil water content. The VWC was measured daily following the water application. The full line indicates the average VWC of 8 pots at each time point. The bands illustrate the 95% confidence intervals.
- Additionalfile5.xlsx
Additional file 5 (.xls): Table S3 Main data supporting the results of this article.
- ESM1.pdf
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This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Research article
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
History
CURRENT STATUS: Posted
Version 3
Posted 30 Dec, 2020
No community comments so far
No comments provided
No comments provided
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Comments: 0
PDF Downloads: ...
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License:
This work is licensed under a CC BY 4.0 License. Read Full License
Background
Climate change will increase the occurrence of plants being simultaneously subjected to drought and pathogen stress. Although it is well known that drought can alter the way in which plants respond to pathogens, knowledge about the effect of concurrent drought and biotic stress on grapevine is scarce. This is especially true for Plasmopara viticola, the causal agent of grapevine downy mildew. This research addresses how vines with different drought tolerances respond to challenge with P. viticola, drought stress or their combination and how one stress affects the other.
Results
Artificial inoculation was performed on two cultivars exposed to full or deficit irrigation in the Mediterranean climate of Cyprus. In parallel, leaf discs from these plants were inoculated under controlled conditions. Leaves were sampled at an early infection stage to determine the influence of the single and combined stresses on oxidative parameters, chlorophyll, and phytohormones. Under irrigation, the local Cypriot cultivar Xynisteri was more susceptible to P. viticola than the drought-sensitive cultivar Chardonnay. Successful infection by P. viticola at 1.5 days post inoculation was associated with high levels of indole-3-acetic acid (IAA), salicylic acid (SA), jasmonic acid (JA), and proline and strong decreases in antioxidant enzyme activity. Drought, on the other hand, triggered the accumulation of IAA and abscisic acid (ABA), which antagonized JA and SA. Exposure to drought stress increased the susceptibility to P. viticola of the leaves inoculated under controlled conditions. Conversely, both cultivars showed resistance against P. viticola when inoculated in planta under continued deficit irrigation. Despite their resistance, the pathogen-associated responses of IAA, antioxidant enzyme activity, and proline still occurred in these drought-stressed plants. Surprisingly, ABA, rather than the generally implicated JA and SA, seemed to play a prominent role in this resistance.
Conclusions
Drought exposure increased the susceptibility of leaves inoculated in vitro. Conversely, deficit irrigation induced resistance to P. viticola in both Chardonnay and Xynisteri plants inoculated in planta. ABA, rather than JA and SA, was implicated in this resistance. The irrigation-dependent susceptibility indicates that the changing climate and the practices used to mitigate its effects may have a profound impact on plant pathogens.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
This is a list of supplementary files associated with this preprint. Click to download.
- Additionalfile1.xlsx
Additional file 1 (.xls): Table S1 P-values for the different factors and interactions retained in the models after model selection. Interaction terms that were not important for the models were removed based on the AIC. The linear regression analyses the interactions between the predictor variables: cultivar (Chardonnay or Xynisteri), irrigation (full or deficit), duration (of the irrigation treatment; 9 or 16 dot), and pathogen (P. viticola or water inoculation). Highlighted cells have p-value < 5% (dark green); 5%< p-value <10% (light green); 10%<p-value<15% (grey).
- Additionalfile2.xlsx
Additional file 2 (.xls): Table S2 Coefficient estimates for the different factors and interactions retained in the models after model selection. Interaction terms that were not important for the models were removed based on the AIC. The linear regression analyses the interactions between the predictor variables: cultivar (Chardonnay or Xynisteri), irrigation (full or deficit), duration (of the irrigation treatment; 9 or 16 dot), and pathogen (P. viticola or water inoculation). Coefficients with a p-value < 15% are highlighted, in a darker shade if the p-value<5%. The colours indicate a positive (blue) or negative (red) correlation.
- Additionalfile3.tiff
Additional file 3 (.tif): Fig. S1 Relative humidity (RH) and temperature during the experiment. The data were recorded every 20 minutes with an on-site data logger in sheltered conditions.
- Additionalfile4.tiff
Additional file 4 (.tif): Fig. S2 Volumetric water content (VWC) of the soil during the experiment. Deficit irrigation (DI) was maintained at 40% of the full irrigation (FI) based on the volumetric pot soil water content. The VWC was measured daily following the water application. The full line indicates the average VWC of 8 pots at each time point. The bands illustrate the 95% confidence intervals.
- Additionalfile5.xlsx
Additional file 5 (.xls): Table S3 Main data supporting the results of this article.
- ESM1.pdf
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