Heterozygosis drives maize hybrids to select elite probiotic Pseudomonas strains among resident soil populations.

By comparing the distribution of genomic and phenotypic markers among rhizospheric Pseudomonas strains recovered from two maize hybrids, with those of strains recovered from their four respective parental lines, we evidenced that both hybrids supported more elite probiotic strains than parents. Elite Pseudomonas strains showed potential for an appropriate in vitro 2,4-diacetylphloroglucinol (DAPG) and auxin (AIA) productivity, and a superior root-colonization ability. The actual biocontrol, root-stimulation and root-colonization abilities of these strains were confirmed by bioassays on five fungal strains and on axenic maize plants. Finally, results on the abundance and genetic diversity of resident probiotic Pseudomonas strains indicated that each hybrid was able to select its own specific probiotic population, while the four parental lines were not. The evidence that heterozygosis can drive maize plants to select elite probiotic rhizospheric DAPG+ -AIA+ Pseudomonas strains opens the way to a new strategy in the set up of plant breeding for low-input and organic agriculture.