Abstract/Summary

Rhizodeposition is an important source of substrate for microbial communities, supporting activitiesincluding soil organic matter (SOM) and nutrient cycling. Therefore, it is a potential trait of interest forcrop plants, particularly in the context of variety selection for sustainable production systems. However,we do not have a good understanding of (i) whether there is significant variation in root-C depositionbetween varieties of important agricultural crops and (ii) whether variation in C deposition betweenvarieties leads to major differences in C cycling in soil. In two experiments, we assessed variations in Cdeposition amongst barley genotypes and their respective impacts on microbial activity and SOM dy-namics. In experiment 1, we applied13CeCO2labelling to selected barley recombinant chromosomesubstitution lines (RCSLs) and traced root-derived C in surface soil CO2efflux, soil microbial biomass-C(MBC), soil solution, and soil particle-size fractions. In experiment 2, we conducted MicroResp analysisusing 15 ecologically relevant C substrates to assess the impacts of barley genotypes on microbial activity.Soil respiration measurements (partitioned into plant- and SOM-derived components) revealedgenotype-specific effects on plant-derived C, SOM-derived C and total C respired as CO2. For particle-sizefractionation, we found that incorporation of plant-derived C to the silt-and-clay fraction varied betweengenotypes, indicating differences in relative stabilization of root-derived C as a result of barley genotype.Our data did not indicate genotype effects on total MBC size or dissolved organic-C (DOC) in soil solu-tions, but significant differences in plant-derived MBC and DOC were observed. MicroResp analysisshowed differential utilization of 7 substrates (glucose, trehalose, lignin, arabinose, alanine, aminobutyricacid and lysine) revealing variation in community level physiological profiles (CLPPs) of soil microbes asimpacted by barley genotypes. Furthermore, we found significant clustering of microbial CLPPs as afunction of RCSLs and parent lines (Caesarea 26-24 and Harrington) suggesting a strong plant geneticcontrol of the barley microbiome, and that this genetic control is heritable. Our results demonstratebarley genotype-specific effects on soil processes, revealing the potential for germplasm selection andvariety improvement in barley to support sustainable production systems.