What Can We Learn from Evolutionary Biology and Natural Ecosystems to Improve Stress Responses?.

Most stress-related adaptations come with tradeoffs. The best strategy to survive long-term flooding is not optimal for short-term flooding. Agaves grow with very little water, but their CAM photosynthesis is limited by storage capacity for organic acids. The hypersensitive reaction protects plants from pathogens that need a living host, but it can be exploited by those that consume dead tissue. So simply transferring stress-related genes, or increasing their expression, is risky.

Fortunately, some tradeoffs that constrain natural selection need not constrain plant breeders. Natural selection favors plants that out-compete their neighbors for resources, but we have bred crops that essentially cooperate to use those resources more efficiently. Natural selection gives adaptation to past conditions, but we can breed crops for future CO₂ concentrations and for resistance to pests and pathogens that have not yet reached our region or, perhaps, have not yet evolved. Natural selection is almost blind to future benefits, but we could breed crops that benefit subsequent crops in the same soil, via more-persistent root channels or by enriching the soil with more-beneficial microbes.

We may learn much by studying the stress-related adaptations of wild plants and landraces, especially in the ecosystems where they evolved. But we need to study the costs and risks of those adaptations, not just their benefits. Only then can we predict which of the genes and strategies that benefited those plants in their environments will be most beneficial in a given agricultural context.