Plant growth promoting rhizobacteria (PGPR) is a group of
free-living bacteria that colonize the rhizosphere (Kloepper
and Schroth 1978). They can promote plant growth,
nutrient and mineral uptake, and also inhibit the harmful
effects of microorganisms (Malik and Pakhshanda 1997;
Figueiredo et al. 2008). PGPR mechanisms can be classified
into direct or indirect promotion. Direct promotion
occurs when compounds synthesized by bacteria, such as
fixed nitrogen, soluble phosphate, phytohormones, and
iron that have been sequestered by bacterial siderophores,
are provided to the plant. Indirect promotion or biological
control occurs when PGPR reduces or prevents the
deleterious effects of phytopathogens.
Bacillus species are widespread in the rhizosphere
which play very important role in microflora of plant rhizosphere.
Since Bacillus species can produce spore, this
genus is more stable than others as a natural biological
control agent. So Bacillus strains with PGPR features
are very useful in sustainable agriculture (Van 2007).
Peanut is an important industrial crop which is mainly
used for extracting oil and direct consuming. It has
high nutritional values because it contains plenty of
fat, protein and vitamin A. China is the largest peanut
producing country in the world accounting for about
two-fifths of the world production. During the process
of planting, harvesting and storing peanuts, they are
always invaded by fungi which produce aflatoxin. In
the most places of southern China, the weather is very
humid and the temperature is high.