Novel hypotheses to be tested concerning the impact of substrates other than host plants on the evolutionary potential of plant pathogens.

aThe evolutionary forces listed here are those that have been considered for plant pathogens in agricultural contexts [56]. These hypotheses concern pathogens with a marked saprophytic phase or for which nonagricultural or nonplant substrates can be a notable reservoir for survival. Reservoirs can include irrigation water, natural waterways and bodies of water, biological vectors (animals, fungi, etc.), abiotic vectors (aerosols, clouds, precipitation), wild plants and weeds, soil, and physical structures in agricultural systems (greenhouse materials, tubing, plastics).