Integrated Screening Identifies Elite Indigenous Bacillus Strains for Enhancing Wheat Productivity and Irrigation...

Water scarcity is a major constraint to wheat production in arid regions, highlighting the need for sustainable approaches to improve crop productivity and irrigation water-use efficiency (IWUE). Although Bacillus-based bioinoculants have been widely investigated, the potential of indigenous strains adapted to arid environments remains underutilized for the developing of site-specific bioinoculants. This study developed an integrated screening strategy combining plant growth-promoting (PGP) traits characterization, greenhouse evaluation, correlation analysis, and multivariate analyses to identify elite indigenous Bacillus strains capable of improving wheat performance under contrasting irrigation regimes. Fifty-one indigenous Bacillus strains representing 19 species, identified by 16S rRNA gene sequencing, were characterized for indole-3-acetic acid (IAA), ammonia (NH₃), siderophore production, and potassium-solubilizing activity and subsequently evaluated in greenhouse conditions under full (FI) and deficit (DI) irrigation. Plant growth was assessed at 85 days after sowing, while yield and yield-related traits were evaluated at physiological maturity (130 DAS). Significant variation was observed among the strains in both PGP traits and their effects on wheat performance. Selected strains increased vegetative growth traits by 22.2-53.7% under FI and 16.4-49.2% under DI, while improving yield-related traits and IWUE by 24.7-52.3% and 14.7-67.2%, respectively, compared with the uninoculated control. Correlation analysis identified IAA production as the PGP trait most strongly associated with wheat growth, grain yield, and IWUE, followed by NH₃ production, whereas siderophore production showed weak associations with most agronomic traits. Hierarchical cluster analysis and principal component analysis consistently identified Bacillus cereus A2, B. pumilus D2 and E3, and B. safensis D5 as the elite strains, while several additional indigenous strains also exhibited considerable potential under both irrigation regimes. This study demonstrates that the integrated screening approach enabled the identification of strain-level differences that could not be adequately captured by individual PGP traits alone, highlighting indigenous Bacillus strains as valuable resources for developing locally adapted bioinoculants to improve wheat productivity, IWUE, and drought resilience in arid and semi-arid agroecosystems.