Agriculture Reference
In-Depth Information
Chapter 9
Microbial strategies for the improvement of
legume production in hostile environments
Dilfuza Egamberdieva
1
, Vyacheslav Shurigin
1
, Subramaniam Gopalakrishnan
2
and Ram Sharma
3
1
Department of Microbiology and Biotechnology, Faculty of Biology and Soil Science, National University of Uzbekistan, Tashkent, Uzbekistan
2
International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesh, India
3
International Center for Agricultural Research in the Dry Areas (ICARDA), Tashkent, Uzbekistan
9.1 Introduction
Legumes are very important crop plants for human
and animal consumption, and the use of legumes in
crop rotations can be a useful management strategy to
increase the supply of nitrogen to non-legume plants
(Lüscher
et al.,
2011; Nyfeler
et al.,
2011). The legume-
Rhizobium
symbiosis is known to be the most efficient
system for biological nitrogen fixation (BNF) through
nodulation in legume roots (Molla
et al.,
2001). It has
been estimated that some 44-66 million tons of N
2
are
fixed annually by leguminous plants, providing nearly
half of all N used in agriculture worldwide (Alberton
et al.,
2006).
The response of legumes to environmental stresses
such as salinity and drought varies and depends on
soil type, salt toxicity and climatic factors (Cordovilla
et al.,
1995; Serraj
et al.,
2001; Predeepa & Ravindran,
2010; Jabborova
et al.,
2013a). Numerous studies have
shown that soil salinity inhibits legume growth and
development and decreases nodulation and N
2
fixation
(reviewed by Zahran, 1999; Mensah & Ihenyen, 2009;
Egamberdieva
et al.,
2013a). Grain legumes are known
to be salt-sensitive crops, but differences in salt toler-
ance exist among genotypes (Dua, 1992; Gandour,
2002). Genotypic variation in leguminous crops for
traits affecting nodulation and N
2
fixation has been
found (Montealegre
et al.,
1995). Bliss (1993) observed
that the selection and breeding of common bean culti-
vars tolerant to salinity could improve nodulation and
N
2
fixation. Thus, the selection of improved chickpea
cultivars with salt-tolerant symbioses is an absolute
necessity to enable its cultivation in salt-affected soils.
Available reports indicate that legumes show improved
Various biotic and abiotic factors limit crop productivity,
affecting nearly 1 billion people around the world
(Munns & Tester, 2008; UNEP 2009). Malnutrition is
recognized as the world's most serious health problem,
while agricultural development is considered as the most
effective sector in reducing hunger and poverty, through
improvements in crop productivity (Godfray
et al.,
2010).
Crop losses due to salinity and drought are a major area
of concern in coping with increasing food requirements
(Egamberdiyeva
et al.,
2007; Shanker & Venkateswarlu,
2011; Davranova
et al.,
2013). Salinity alone affects 33%
of the world's potential arable land, whereas 950 million
ha of salt-affected lands occur in arid and semi-arid
regions (UNEP, 2008). Major factors increasing salinity
include irrigation of cultivated lands with saline water,
poor cultural practices and low precipitation. The ability
of plants to take up water are inhibited by salinity
stress, causing ion imbalance and, in turn, resulting in
a reduction of root and shoot growth (Munns, 2002).
In such situations, the presence of salt-tolerant genetic
variants in a particular crop is a prerequisite for its
successful cultivation (Mahmood
et al.,
2000). Numerous
studies have been reported on the management and
identification of salt-tolerant crops such as cotton, wheat,
maize and alfalfa (Chauhan & Singh, 2000; Soltani
et al.,
2012). In addition, organic farming practices, such
as application of farm manure, compost, biofertilizer and
recycling of crop residues and/or green manures, also
improve degraded soils affected by salinity (Pathma &
Sakthivel, 2012; Adesemoye & Egamberdieva, 2013).
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