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Control of Zymoseptoria tritici a splash dispersed pathogen by the mean of wheat cultivars mixture; experimental and modelling biophysical approaches

S Saint-Jean: UMR ECOSYS AgroParisTech, INRA, Université Paris-Saclay

<div>Growing together mixture of cultivars with contrasting level of resistance to disease has been shown as a way of reducing fungal aerial disease severity on crops. In order to improve the design of cultivar mixture for reducing splash dispersed diseases such as septoria tritici blotch, caused by <em>Zymoseptoria tritici</em>, our objective is to understand the role of the canopy architecture of wheat cultivar mixture. Two mechanisms related to the effect of canopy architecture on the epidemiological are studied here. The first one is the impact of architecture of each cultivar on the barrier effect provided by resistant plants among susceptible plants that reduce the dispersion of fungal spore. The second one is the possible modification of the microclimate within the mixture compared to pure stand that could foster some epidemiological processes. We used a mechanistic modelling approach within an explicit description of canopy architecture and splash dispersal processes. Dispersal patterns in cultivar mixtures with either similar (70 cm height) or contrasted straw height (120 cm and 70 cm) were compared. Spore interception on susceptible plants was lower when the susceptible cultivar was mixed with a tall resistant cultivar rather than with a resistant cultivar of the same height. This result was confirmed with field experiments with a reduction of AUDPC close to 50%. Field experiments show also that within denser canopy the barrier effect is enhanced but on the other hand the leaf wetness duration increased and could foster the disease. These results suggest that considering cultivar architecture in mixture design is as an additional lever to enhance mixture effects on foliar splash-dispersed diseases.</div>