Abstract:
Endophytic bacteria colonize in plant tissues and e
nhance plant growth by a wide
variety of mechanisms. The objectives of this study
were to examine the population of root
endophytic bacteria in soybean and corn, and to ide
ntify IAA-producing endophytic
bacterial strains and their growth promoting effect
. The density of endophytic bacteria
varied irrespective of crops, sampling times and so
il amendments. A total of 119 and 277
bacterial isolates were isolated from soybean and c
orn roots, respectively. 39.6% of the
total isolates showed IAA production in the range o
f 1~23
μ
g mL
-1
in culture medium
supplemented with tryptophan. Fourteen isolates, de
signated as S1-S4 from soybean roots
and C1-C10 from corn roots, had the capacity of pro
ducing IAA over 10 mg L
-1
. Based on
16S rRNA gene sequence analysis, the fourteen isola
tes were closely related to
Psychrobacillus
,
Microbacterium, Lysinibacillus
and
Bacillus
. Pot experiment indicated
that the growth-promoting effects varied among thes
e 14 bacterial strains and not all of
the strains were able to promote growth of the test
ed soybean and wheat plants. Strains
Microbacterium
sp. C4 and
Lysinibacillus
sp. C7 showed better performances in
promoting soybean and wheat seedling growth.
Keywords:
Endophytic bacteria, Enhancement, IAA, Root, Plant
growth