A major concern in a changing climate is sustainably feeding the next billion people. Increasing grain production in plants has occurred mainly by selecting for above-ground traits specifically based on visual assessment or easily visible traits. This has meant that root traits which might increase yields have often been neglected in breeding programs because roots are hidden in opaque soil. Also, the agricultural environment is heterogeneous in terms of nutrient distributions in the soil and competition is ubiquitous. Thus, plants in a community might evolve non-optimal root traits that are undesirable in agriculture such as ignoring nutrient patches and root over-proliferation at the cost of a lower population yield. We phenotyped 20 soybean genotypes for root traits to identify: i) soybean’s response to nutrient rich patches of soil, ii) soybean’s root response to the roots of neighboring plants, and; iii) how foraging for nutrients and presence of a neighbor affect soybean yield. Plants were grown alone (individual plant per pot) or with neighbors (two plants per pot, competition treatment) and an organic nutrient patch was created in all pots. We monitored root growth in alone and competition treatments and toward and away the patch using a minirhizotron camera. We concluded the study using the existing game-theoretic model.
Results/Conclusions
There was no variation among genotypes in their foraging strategies for nutrient patch and neighbors did not influence it. All genotypes treated nutrient patch and poor zones equally. Root over-proliferation was manifest in all genotypes when grown with a neighbor compared with alone treatment suggesting that plant engaged in tragedy of the commons game. Although, all genotypes produced more roots at the presence of a neighbor, pod weight was not significantly different from plants grown alone indicating that root over-proliferation did not lead to yield loss. We tested the root and yield production of plants to neighbors using game theoretic model. The model predicted that If plants engage in a game-theoretic strategy, the evolutionarily stable strategy of root production is always greater than root production when grown alone. Although in most cases over-proliferating roots are at the cost of yield, based on the model it is possible that plant produce as much yield in alone treatment as at the presence of a neighbor. But if root over-proliferation does not have benefits for the plant in terms of increased yield, this extra carbon could be invested in reproduction organs and leads to increased yield.