To do this, we built a stochastic model to estimate the time of emergence of a pathogen mutant adapted to a multigenic resistance carried by a host population. Multigenic plant resistance is defined as a combination of major resistance genes that confer total immunity to disease. Total resistance can also be conferred to host individuals that only have a subset of these major genes (referred to as hosts with incomplete combinations).

Our results reveal the importance of the stochastic migration process to the adaptive dynamics of the pathogen. Firstly, we identify the growth and migration rates that allow pathogens to rapidly adapt to a multiresistance, even if only a small proportion of resistant hosts is introduced (figure). Secondly, the model highlights the negative impact of hosts that carry "incomplete" combinations on the durability of multiresistances. In fact, associating hosts that carry the multiresistance with susceptible hosts that carry one or several independently bypassed resistance genes can be more durable than associating them with hosts that carry "incomplete" combinations that include only a subset of the major genes. Third-ly, in contrast to the accepted view, our model suggests that multiresistance durability should not systematically be identified with mutation cost. Our theoretical study therefore allows us to gain insights into the principles of durable management of multigenic plant resistance for the purpose of hindering the adaptation of harmful populations.

Contact :

Natalia Sapoukhina,  IRHS unit
natalia.sapoukhina@angers.inra.fr

Référence :

• Bourget R., Chaumont L., Sapoukhina N. (2013). Timing of pathogen adaptation to a multicomponent Treatment. PLoS ONE, 8(8): e71926.