Agriculture Reference
In-Depth Information
Chapter 11
R
HIZOBIUM
L
EGUMINOSARUM
I
SOLATED FROM
A
GRICULTURAL
E
COSYSTEMS
S
UBJECTED TO
D
IFFERENT
C
LIMATIC
I
NFLUENCES
:
T
HE
R
ELATION
B
ETWEEN
G
ENETIC
D
IVERSITY
,
S
ALT
T
OLERANCE
AND
N
ODULATION
E
FFICIENCY
S.I.A. Pereira
1
, A.I.G. Lima and E.M.A.P. Figueira
1
Centre for Cell Biology, Department of Biology, Campus Santiago,
3810-193 AVEIRO, Portugal
A
BSTRACT
Salinity is a major environmental constraint of crop production, and with the climate
changes that are being announced for the next decades, like global warming or local
reduction of rainfall, this problem will be amplified. Salinity stress negatively impacts
agricultural yield throughout the world affecting production whether it is for subsistence
or economic gain.
Rhizobium
has considerable scientific, economical and ecological
interest because of their ability to establish nitrogen-fixing nodules on leguminous hosts.
This feature enables plants to grow in soils with low nitrogen levels, to achieve good crop
yields without massive nitrogen fertilization, and, as a consequence, to decrease the
contamination of water reservoirs by inorganic nitrogen compounds. Salinity not only
affects free-living rhizobia but also considerably restrains the nodulation process and
symbiotic nitrogen fixation. To fix nitrogen in saline environments leguminous plants
require both free-living rhizobia and hosts tolerant to salt. Therefore, the selection of
tolerant phenotypes, which can withstand the negative impact of saline soils, can be of
great use to improve nitrogen fixation and productivity in salt-affected soils.
In this work
Rhizobium
was isolated from several locations in Portugal with different
environmental conditions.
Rhizobium
isolates were screened for their tolerance to salinity
as free-living organisms and for their efficiency to fix N
2
under salt conditions in
