Agriculture Reference
In-Depth Information
physiological plant-promotion characteristics (e.g., N-fixation, P-mobilization,
antagonism, phytohormone production, and others) may vary with soil and weather
parameters, and (3) indigenous strains, when isolated, added to the seed in high
numbers, and planted in the same geographical region, under favorable moisture
and temperature conditions, will establish themselves in the rhizosphere of crops
(H
¨
flich et al.
1994
; Pandey et al.
2006a
). Nevertheless, in apparent contradiction
with these premises, Pandey et al. (
1998
) tested the effectiveness of well-known
mesophilic PGPR inoculants—such as
Azotobacter chroococcum
and
Azospirillum
brasilense
—on the promotion of maize growth in colder (
¼
higher) locations of
Sikkim Himalaya. A statistically significant positive effect on the
A. chroococcum
inoculated plants was observed when they were grown under subtropical conditions
(1,200 m altitude). On the contrary, bacterial inoculations were found to be inef-
fective at the temperate site (1,900 m altitude). In a similar investigation,
Egamberdiyeva and H¨flich (
2003
) assessed the impact of mesophilic PS-PGPR
on wheat plants grown at low temperatures (16
C) and under greenhouse condi-
tions (pot experiments). The bacteria used previously isolated from the
phyllosphere, rhizosphere, or soil of the root zone of different crops were not
described as psychrophilic or even psychrotolerant and were isolated instead from
two distant regions of the world (i.e., Germany and Uzbekistan). Inoculation of
seedlings with
P. fluorescens
PsIA12,
Pantoea agglomerans
050309, and
Myco-
bacterium
sp. 44 (the three of them isolated from M¨ncheberg, a German region
with semi-continental climate) was found to significantly increase the root and
shoot growth of winter wheat at 16
C compared to 26
C in loamy sand. On the
other hand,
Mycobacterium phlei
MbP18 and
Mycoplana bullata
MpB46, both
isolated from the semiarid region of Tashkent in Uzbekistan, significantly increased
root and shoot growth of wheat in nutrient-poor Calcisol at 38
C and in nutrient-
rich loamy sand at 16
C. Furthermore, the inoculated wheat plants had significantly
higher N, P, and K contents. In addition, some of these bacterial isolates could
survive and establish better at 16
C than at 26
C, in the rhizosphere of winter
wheat and in the bulk soil.
Apart from these pioneer experiments, later efforts were directed toward isolat-
ing indigenous CT-PSB from natural environments of cold mountainous regions
and subsequently testing them as potential PGPB under different conditions. With
the exception of one study conducted with bacterial isolates obtained from ginseng
rhizospheric soil in South Korea (Park et al.
2010
) and another one conducted with
a bacterial strain naturally colonizing the rhizosphere of Antarctic hair grass
(Berrıos et al.
2013
), all the other studies conducted so far have involved bacterial
strains isolated from either rhizospheric or bulk soil fractions collected at different
alpine and sub-alpine locations in the IHR. Not surprisingly, major findings on this
subject have come mainly from several Indian research groups. Besides, one of the
main outcomes of this effort was the establishment of a culture collection of native
“high altitude bacteria,” allowing characterization of some selected isolates for
plant growth promotion and biocontrol, with special reference to their adaptability
to low temperatures (Pandey et al.
2004
,
2006a
) (Fig.
5.1
).
