Using wheat cultivar mixtures to reduce severity of Septoria tritici blotch, a rain-borne disease.
Gigot , Christophe (INRA , Thiverval-Grignon (France). UMR 1091 Environnement et Grandes Cultures) | Saint-Jean , S (AgroPariTech, Thiverval-Grignon(France). UMR EGC) | Huber , Laurent (INRA , Thiverval-Grignon (France). UMR 1091 Environnement et Grandes Cultures) | Leconte , Marc (INRA , Thiverval-Grignon (France). UR 1290 BIOlogie GEstion des Risques en agriculture - Champignons Pathogènes des Plantes) | Maumené , C (Institut du Végétal, Boigneville(France).) | Pope De Vallavieille , Claude (INRA , Thiverval-Grignon (France). UR 1290 BIOlogie GEstion des Risques en agriculture - Champignons Pathogènes des Plantes)
Increasing plant diversity using cultivar mixtures is a worthwhile strategy that has been shown as a way of reducing wind-borne disease severity on crops and prolonging the efficacy period of plant resistance genes. The relevancy of this cultural practice remains to be assessed in the case of rain-borne diseases, such as septoria tritici blotch. This last one, due to the pathogen fungus Mycosphaerella graminicola, is a predominant foliar disease on wheat crops, able to cause substantial yield losses (up to 40%). Field experiments were conducted on a binary wheat mixture, with a 1:3 susceptible:moderately high resistant ratio, at Grignon (Yvelines, France) every year since 2008. The results showed a consistent decrease of septoria tritici blotch severity on the more susceptible cultivar (on average, 42% less pycnidial leaf area on the three upper leaves), without significantly affecting the more resistant cultivar, comparatively to their respective pure stands. In addition, a mechanistic-stochastic model is specifically developed to describe the progression of septoria tritici blotch within a heterogeneous virtual 3D-canopy. This theoretical approach combines physics and epidemiology, firstly, to compute the raindrop interceptions with the plant organs and the trajectories of the rain-splash droplets within the canopy, and secondly, to take into account the cultivar resistance levels and the polycyclic nature of the pathogen agent. This model will be first compared with the experimental results, and then, it will be aimed to extend our findings to other cultivar mixture conditions such as cultivar proportions or cultivar spatial distributions.
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