Plant neighbour-modulated susceptibility to pathogens in intraspecific mixtures.

As part of a trend towards diversifying cultivated areas, varietal mixtures are regaining attention to manage diseases. Besides the epidemiological effects of varietal mixtures on pathogen propagation, little is known about the effect of intra-specific plant-plant interactions and their impact on plant response to disease. Genotypes of rice or durum wheat were grown with different conspecific neighbours and manually inoculated under conditions preventing pathogen propagation. We measured their disease susceptibility and the expression of basal immunity genes as part of the response to intra-specific neighbours. The results show for both rice and wheat that susceptibility to pathogens and immunity is modified in many instances by the presence of intra-specific neighbours. . This phenomenon, that we termed 'Neighbour-Modulated Susceptibility' (NMS), could be caused by the production of belowground signals and does not require the neighbours to be infected. Our study calls for a revisiting of the mechanisms reducing disease in varietal mixtures in the field.