Genotype-dependent salt tolerance is associated with the specific recruitment and assembly of rhizosphere bacterial communities in Amaranthus spp.

The impact of plant genotype on host-microbiome interactions and plant performance under salt stress is not well understood. This study examined 100 grain amaranth ( Amaranthus spp.) varieties under salt stress in lab and field settings. Varieties were divided into four quadrants (Q1-Q4) based on their growth responses. Q1 varieties enriched beneficial bacteria and carbohydrate metabolism, forming a strong network for stress resistance. Q2 varieties attracted stress-tolerant and predatory bacteria, creating a sparse network to activate stress-mitigation pathways. Q3 varieties recruited a diverse microbial community with a modular network, suggesting a metabolic response similar to an active cry for help under stress. Q4 varieties were enhanced with salt-tolerant, spore-forming bacteria, forming a network with similar functions, indicating adaptation to harsh conditions. Our results indicate that both taxonomy and geographic source are significantly associated with phenotypic variation in Amaranthus spp., and that this phenotypic variation covaries with the recruitment and composition of rhizosphere bacterial communities.