Pore architecture of rhizosphere soil
The soils used in the experiments had contrasting physical and chemical
properties (Table S1). Hence, the contribution of rhizosphere soil
architecture to the diversity of root microbiome was assessed using
micro-CT scan. Firstly, we calculated soil porosity (based on micro-CT
observed >30 µm diameter pores) at the inner rhizosphere
zone (0-1 mm from root, Fig. 6a) relative to the outer rhizosphere zone
(1-2 mm from root), and found an interaction between the effect of soil
type and root segment was significant (P < 0.01, Fig S7),
while genotype was not. The variation in soil porosity (rhizosphere :
bulk soil) between different soil types was large at basal rhizosphere,
but small at apical rhizosphere (Fig S7). The regression analysis using
5 soil types × 3 chickpea genotypes identified a positive correlation of
rhizosphere soil porosity with abundance of phylum Actinobacteria,
Acidobacteria, and Chloroflexi in the rhizosphere relative to bulk soil
(P < 0.01, Fig. 6), but was negative with phylum Firmicutes
and one core ASV, ASV17781: unclassified Micrococcaceae, (P <
0.05, Fig. 6a and 6b). These significant correlations were only detected
in the rhizosphere of the basal root.