Heterozygosis drives maize hybrids to select elite 2,4- diacethylphloroglucinol-producing Pseudomonas strains among resident soil populations

By comparing the distribution of two genomic markers among Pseudomonas strains recovered from the rhizosphere of two maize hybrids with those of strains recovered from the rhizosphere of their four respective parental lines, we showed that both hybrids supported more elite probiotic strains than the parents. Elite Pseudomonas strains showed genomic potential for both an appropriate in vitro 2,4-diacetylphloroglucinol (DAPG) productivity, and a superior root-colonization ability. The actual biocontrol and root-colonization abilities of these strains were confirmed by bioassays on five fungal strains and on axenic maize plants. Furthermore, results on the abundance and genetic diversity of resident DAPG Pseudomonas strains indicated that each hybrid was able to select its own specific DAPG population, whereas the four parental lines were not. The evidence that heterozygosis can drive maize plants to select elite probiotic rhizospheric DAPG Pseudomonas strains opens the way to a new strategy in the set up of plant breeding for low-input and organic agriculture. © 2006 Federation of European Microbiological Societies.