STUDIES ON POPULATION DYNAMICS OF RHIZOSPHERE AND NON RHIZOSPHERE SOIL BACTERIA IN CHIRPINE AND DEODAR FORESTS AS INFLUENCED BY DIFFERENT ALTITUDINAL RANGES OF HIMACHAL PRADESH
Abstract
ABSTRACT
Species diversity refers to the richness of species and also balanced species distribution. Forests are
essential for the availability of a variety of ecosystem services that are crucial to human well-being and also are
critical habitats for the wide range of biological diversity. The high spatial variation in microbial activity is due
to the spatial heterogeneity of forest soils (e.g. enzyme activity or respiration) and microbial biomass content.
Coniferous trees are cosmopolitan within the world and have tremendous environmental and economic
importance. Large numbers of bacteria resides in the rhizosphere or rhizoplane of their roots, and a few of those
may promote tree growth through various mechanisms. Tree species like Pinus roxburghii Sarg. (chirpine) and
Cedrus deodara (Roxb.) Loud (deodar) are known among the foremost magnificent conifer trees for the
dynamic bacterial communities due to decomposing organic matter under these trees. Though lots of research
has been done on PGPR in agricultural systems yet research on this bacterial group in forest ecosystem remains
at its nascent stage. Hence, investigation entitled “Studies on population dynamics of rhizosphere and non
rhizosphere soil bacteria in chirpine and deodar forests as influenced by different altitudinal ranges of Himachal
Pradesh” was carried out to explore the diversity of plant growth promoting rhizosphere and non rhizosphere
soil bacterial communities associated with Cedrus deodara and Pinus roxburghii and their characterization for
plant growth promoting traits followed by their genetic diversity. A total of 168 rhizospheric and non
rhizospheric bacteria were isolated from soil samples of Cedrus deodara and Pinus roxburghii collected from
four different sites of Shimla, Kullu, Solan and Sirmour valleys of Himachal Pradesh. A significant variation
was recorded in rhizosphere and non rhizosphere bacterial population in deodar and chirpine which increases
from lower to higher altitude. All these bacterial isolates were screened for multifarious plant growth promoting
traits i.e. P-solubilzation shown by 76.78% , siderophore production shown by 79.16%, IAA shown by 69.04%
of isolates and zinc solubilization was shown by 76.78% of total isolates. Maximum plant growth promoting
traits were shown by rhizosphere soil samples of deodar. After this, they were subjected to test for various
antagonistic traits (HCN, Chitinase, Protease, Amylase) and also test for antifungal against Fusarium sp. and
Phytophthora sp. Fifty seven isolates exhibiting maximum PGP traits were subjected to study their biochemical
tests. Then, a total of 19 representative isolates were selected to study genetic diversity among them using 16S
rDNA sequencing. In silico analysis grouped these isolates into three major genera i.e. Bacillus and
Pseudomonas being predominant while other is Alcaligenes. Overall, present study conclude that, isolates from
rhizosphere soil exhibit higher multifarious PGP traits than non-rhizosphere soil. Also the soil under deodar is
well enriched by various soil nutrients which supports the proliferation of large number of beneficial bacteria as
compared to chirpine forests.