Weather conditions conducive to infection of winter wheat by Puccinia striiformis sp. tritici race ‘warrior’ 1*
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Moussa El Jarroudi , Louis Kouadio , Mustapha El Jarroudi , Clive Bock , Bernard Tychon , Jürgen Junk , Philippe Delfosse 1
Department of Environmental Sciences and Management, Université de Liège, Arlon, Belgium; 2 ICACS, University of Southern Queensland, Toowoomba, Australia; 3 LMA, FST Tanger, Université Abdelmalek Essaâdi, Tangier, Morocco; 4 USDA-ARS-SEFTNRL, 21 Dunbar Road, Byron, GA 31008, USA; 5 Luxembourg Institute of Science and Technology, Esch/Alzette, L-4362 Grand Duché de Luxembourg. * Email:
[email protected]
Introduction Wheat stripe rust (WSR), caused by the biotrophic fungal pathogen Puccinia striiformis Westend. f. sp. sp. tritici Ericks, Ericks, is one of the most damaging diseases of wheat in many areas around the world (Hovmøller et al. 2011). This disease has been identified for the first time in the Grand Duchy of Luxembourg (GDL) in 1999 (El Jarroudi et al. 2009a). A recently isolated strain of P. striiformis sp. tritici, tritici, ‘warrior’, first identified in 2011 in Europe, is now virulent on adult plants of susceptible wheat cultivars throughout most wheat growing regions, including Luxembourg (Sørensen (Sørensen et al. 2014) . The objectives of this study were to determine favourable weather conditions conducive to the infection of wheat by P. striiformis in GDL through (i) analysing Dennis model outputs generated using a Monte Carlo method, and (ii) identifying the best correlation between the frequencies of weather condition classes and the area under under the disease progress curve on the uppermost three leaves (L1, L2, and L3; L1 being the flag leaf).
Results and Discussions
Materials and Methods Experimental fields
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size). WSR was monitored on the 3 upper leaves (L3-L1) in non-fungicide treated plots throughout the cropping season.
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Infection by Temperature
a2
90
60
Description of the stochastic approach
r=0.83
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r=0.65
200 100 0
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r=0.94*
r=0.75 r=0.68
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7°c80%, >90 %) for 4 intervals of temperatures (4°< T < 7°C, 7°< T < 15°C, 15° < T < 16°C,
- El Jarroudi M., Delfosse P., Maraite H., Hoffmann L., Tychon B. (2009b) Assessing the accuracy of simulation model for Septoria leaf blotch disease progress on winter wheat. Plant Dis 93:983-992 .
and T > 16°C) associated to presence of rain; іі) RH 15°C, associated to an absence of rain, ; ііі) 4°< T < 7°C without considering RH and rain; іv) 7°< T < 15°C with-
- Hovmøller MS, Sørensen CK, Walter S, Justesen AF (2011) Diversity of Puccinia striiformis on cereals and grasses. Annu Rev Phytopathol 49:197-217.
out considering RH and rain.
- Sørensen CK, Hovmøller MS, Leconte M, Dedryver F, de Vallavieille-Pope C (2014) New races of Puccinia striiformis found in Europe reveal race specificity of long-term effective adult plant resistance in wheat. Phytopathology 104:10421051.
Correlations between the proportion (%) of each of the classes and the standard AUDPC
- Zadoks JC (1971) Systems analysis and the dynamics of epidemics. Phytopathology 61:600-610.
of L1, L2 and L3 were then analysed.
Support & Acknowledgements
Additionally, the capability of our threshold-based approach to correctly simulate the occurrence of WSR on upper leaves at the end of the latency period was evaluated. We assumed that potential inoculum was already present in fields. The latency period was calculated by Zadoks’s equation (Zadoks, 1971). This evaluation was based on contingency scores for the variables probability of detection (POD), false alarm ratio (FAR), and critical success index (CSI) of WSR, as described by El Jarroudi et al. (2009b).
Fig. 3. Number of hours per day of high probability of WSR infections
Fig.4. Leaf area development, wheat stripe rust (WSR) development, and simulated WSR infections on the three upper leaves. Christnach, 2012 cropping season.
We would like to thank the Ministry of Culture, Higher education and Scientific Research of the Grand-Duchy of Luxembourg for contributing to the funding of this research. We are grateful to Guy Reiland, Guy Mirgain, Marc Kails, and Alexandre Nuttens for their technical support.
