Rhizobacteria are not known to colonize the roots of cereal crops, typically only only legumes. You would think that scientists would spend more effort trying to create "super" rhizobacteria that can colonize even more aggressively and also fix many times more nitrogen than ordinary ones. I cannot say this one below has independent reviews by well published agroscientists, but it's a step in the right direction:

https://soilscapesolutions.com/products/RhizoGenesis-p668356...

Do a Google search: Methods for Breeding "Super Strains"

Chemical Mutagenesis: Scientists expose the rhizobacteria to alkylating agents like Ethyl methanesulfonate (EMS) to force point mutations.

Physical Radiation: Exposing bacterial cultures to UV light or gamma rays breaks DNA strands, inducing random repair variations.

Experimental Evolution: Google it.