Response of Wheat Root System and its Mineralization to Chemical Inputs, Plant Genotype and Phenotypic Plasticity

Agricultural lands represent vast terrestrial surfaces, in which agricultural practices are likely to offer leverages to store carbon in soil. We hypothesize that ancient wheat varieties could store more carbon than modern ones, due to a likely bigger and deeper root system. Since modern varieties are often cultivated using synthetic chemical inputs known to modify soil carbon dynamics, it is important to decouple the effect of breeding types (ancient versus modern varieties) and inputs to assess breeding type’s storing potential. We conducted a field experiment with four modern and four ancient varieties, with and without chemical inputs (nitrogen, herbicide and fungicide). Root morphology was assessed by image analysis, potential catabolic activities of specific substrates (fructose, alanine, citric acid) by MicroResp™ and overall CO 2 emissions by incubating soil and roots from each modality of the experiment for 60 days. Results show that the breeding type did not affect root traits, substrates respiration nor overall CO 2 emissions in our environmental conditions. Application of inputs did not affect root traits but influenced the respiration of specific substrates and CO 2 emissions. The most noticeable response was due to the “breeding type x inputs” interaction : inputs increased CO 2 emissions from soil and root tissues of ancient varieties by 19%, whereas no effect was observed for modern varieties. Taken together, our results did not support the hypothesis that ancient varieties produce more root biomass and more recalcitrant root tissues. It is thus unlikely that they could be more performant than modern ones in storing carbon