Microbial Consortium Application Under Temperature Stress: Effects on the Rhizosphere Microbiome and Plant Growth

The aim of the present study was to investigate the effect of a synthetic microbial consortium (SMC) containing five functionally different bacterial strains (<i>Rahnella aquatilis</i>, <i>Rothia endophytica</i>, <i>Stenotrophomonas indicatrix</i>, <i>Burkholderia contaminans</i>, <i>Lelliotia amnigena</i>) on the growth and development of three agricultural crops (wheat, buckwheat, and rapeseed) on two soil types (chernozem and gray forest soil) under field conditions. The experiment was conducted from June to September 2024 under extreme field conditions, with temperatures reaching 43.8 °C. This study evaluates SMC efficacy under severe abiotic stress, reflecting increasingly common climate extremes. Metagenomic data analysis showed that the introduced strains did not establish stable populations in the soil, possibly due to heat-induced bacterial mortality, though other factors including competition with indigenous microflora and lack of protective formulations may have also contributed. No statistically significant effects on plant morphometric parameters were observed. The extreme temperature and water stress conditions appear to have been the dominant limiting factors, overriding any potential benefits from microbial inoculation, as evidenced by the lack of response to mineral fertilizer application as well. Crop-specific effects were revealed: when cultivating rapeseed on chernozem, a significant increase in available phosphorus content was noted (from 278 ± 45 to 638 ± 92 mg/kg with SMC application, <i>p</i> < 0.001).