The games plant viruses play

•The outcome of mixed virus plant infections is complex and hard to predict.•Game theory provides tools to study interactions between viruses.•Mutual cooperation is the most commonly game played by plant viruses.•Molecular biology of viruses may explain how certain games are played.

Mixed virus infections in plants are common in nature. The outcome of such virus-virus interactions ranges from cooperation and coexistence (synergism) to mutual exclusion (antagonism). A priori, the outcome of mixed infections is hard to predict. To date, the analyses of plant virus mixed infections were limited to reports of emerging symptoms and/or to qualitative, at best quantitative, descriptions of the accumulation of both viruses. Here, we show that evolutionary game theory provides an adequate theoretical framework to analyze mixed viral infections and to predict the long-term evolution of the mixed populations.