Increasing cooperation among plants,symbionts, and farmers is key to past and future progress in agriculture

The collective welfare of crop plants, their microbial symbionts, farmers, and society can be undermined by tragedies of the commons. A crop could increase resource allocation to grain if each plant invested less in sending roots into soil already explored by neighbors and less in stem growth. But evolutionary fitness depends on which plants capture the most soil resources and light (e.g., by growing taller than their neighbors), not just on the efficiency with which those resources are used. As for symbionts, with several strains infecting each plant, only host-imposed sanctions limit the fitness of strains that divert more resources to their own reproduction, at the expense of activities that benefit their host plant. Similarly, individual farmers do not necessarily benefit from pest- and resource-management practices that benefit farmers collectively or society as a whole. Plant breeders have increased crop yields by reversing past selection for individual fitness and they could breed for crops that would favor more-cooperative microbial symbionts. Better aligning interests among farmers and society may be more difficult.