Extremophile Legumes As Guides Toward Development of More Climate-Resilient Legume Crops

Denison, Kiers, and West argued in their 2003 paper, "Darwinian Agriculture," that "most simple, tradeoff-free options to increase competitiveness (e.g., increased gene expression, or minor modifications of existing plant genes) have already been tested by natural selection. Further genetic improvement of crop yield potential over the next decade will mainly involve tradeoffs, either between fitness in past versus present environments, or between individual competitiveness and the collective performance of plant communities." The implication is that evolutionary crucial traits such as photosynthetic efficiency and water use efficiency are likely already to have been explored over evolutionary time and optimized relative to other constraints of a given plant in its natural environment. Extending this logic, for many of our dominant crops, it may not be possible breed varieties that will tolerate dramatically different or extreme environments simply by making incremental changes along narrow physiological dimensions. Instead, we may need to look for more radical adaptations - either by looking for existing extremophile plants to domesticate, or by altering and managing plant growth environments, or by introducing large changes into existing crop species. Considering only individuals in the legume plant family, some adaptations for extreme environments include: perenniality (to beter utilize seasonal precipitation and temperatures); novel root structures for phosphorous uptake; tubers or thickened roots (for water and energy storage); photosynthetic stems and reduced leaves; optimization of leaf orientation for heat avoidance; and modified placement of flowers for improved temperature conditions.