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