Manipulating root-associated microbiomes to boost drought resistance in dryland winter wheat with Streptomyces pactum Act12

Drought critically compromises agricultural productivity and threatens sustainable wheat production. Streptomyces pactum Act12 confers benefits to plant growth under drought stress, but its possible effects on root-associated microbiomes remain understudied. Here, shotgun metagenome sequencing and culture-dependent approaches were integrated to investigate the responses of rhizosphere and rhizoplane microbiomes in dryland winter wheat to exogenous S. pactum Act12 and their potential linkage to plant drought resistance. Seed biopriming with S. pactum Act12 increased plant aboveground dry weight at flowering (by 63.2%) and maturation (by 41.9%) stages, leading to improved grain yield (by 8.7%). Microbial inoculation reduced malondialdehyde contents in wheat leaves and roots at the flowering stage alongside compartment-specific alterations in soil microbiomes. Metagenomic analysis revealed inoculation-induced enrichment of distinct taxa in rhizosphere soils (flowering: Fibrobacterota, Altererythrobacter; maturation: Mucoromycota, Rhodospirillum) and rhizoplane soils (flowering: Pseudomonadota, Serratia; maturation: Candidatus_Pacebacteria, Variovorax). Functional profiling showed up-regulation of key pathways related to oxidative phosphorylation in inoculated rhizosphere soils at the flowering stage. In rhizoplane soils, ABC transporters and pyrimidine metabolism were up-regulated across stages upon inoculation. Two key strains isolated from rhizoplane soils, designated Glycomyces lechevalierae A4 and Microbacterium algeriense B3, demonstrated the ability to enhance drought resistance in wheat seedlings. Inoculation of S. pactum Act12 heightens drought resistance in dryland winter wheat through compartment-specific phylogenetic restructuring and functional reprogramming of root-associated microbiomes.