Frunkranz and Berg [6] reviewed that plant growth
promoting bacteria (PGPB) and biological control
agents (BCAs) impart beneficial effects on plants via
direct and indirect mechanisms. PGPB directly serve
the plants by supplying nutrients (e.g. via the fixation of
atmospheric nitrogen (N2), phosphorous (P)
solubilization, segregation of iron (Fe) by
siderophores), by means of phytohormone synthesis
(e.g. indole-3-acetic acid, IAA), and by lowering the
hosts ethylene level due to ACC deaminase activity.
BCAs support plant health via the suppression of plant
pathogens, e.g. due to competition for nutrients and
space, the synthesis of antimicrobial compounds,
parasitism, or the induction of systemic resistance in
host plants. These plant growth promoting (PGP) traits
can be assessed under laboratory conditions and allow
the selection of strains that could lead to increased
plant growth [