Omics approaches and abiotic stress tolerance in legumes - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 215

Chapter 13

Omics approaches and abiotic stress
tolerance in legumes

Syeda Fatma Hasan Bukhari 1 , Sadia Arshad 1 , Mohamed Mahgoub Azooz 2 and Alvina Gul Kazi 1
1 Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology (NUST), Islamabad, Pakistan
2 Department of Botany, Faculty of Science, South Valley University, Qena, Egypt

13.1 Introduction

Given their great economic and commercial impor-
tance, it is unfortunate that legumes have not been
given as much priority as cereals when improving
crop yield. This could partly be due to the abiotic
stresses under which legumes are often cultivated.
The major abiotic stresses are high temperature,
salinity, water stress, acidity, sodicity and nutrient
deficiencies (Reddy et al., 2012; Mantri et al., 2013;
Varshney & Kudapa, 2013). Such stresses not only
greatly decrease the crop yield and growth but also
negatively affect the formation and function of the
symbiotic relationship between legumes and rhizobia
(Chalk et al., 2010).
Temperature has a marked effect on the plant's
survival, growth and formation of root nodules. Very
high temperatures can therefore lead to reduced crop
yield. Drought is another abiotic stress factor that has
dire consequences on crop yield. The growth of shoots
and roots is greatly decreased in high temperature -
so much so that the roots may actually die (Brisson
et al., 2010). Moreover, plants can suffer poor pollina-
tion if the temperature remains high. The effect of
drought is largely dependent on the duration and
magnitude of the stress to which the plant is exposed.
Drought conditions hinder legume symbiotic per-
formance, retard growth and lead to extremely poor
crop yields (Arrese-Igor et al., 2011). In a study car-
ried out by Basu et al. (2007), it was shown that under
conditions of drought stress, eight cultivars of peas
underwent starch glucose augmentation of hexose
phosphates. Also, a decrease in leaf photosynthesis
was observed.

Legumes characteristically have an unusual flower
structure; their fruit is podded and approximately 88%
of the known species have the ability to form rhizobial
nodules (Udvardi et & Poole, 2013), i.e. an association of
the roots with symbiotic diazotrophs (rhizobia). Both
organisms benefit from this association. The rhizobia
are provided with energy in the form of amino acids by
the plant whereas the rhizobia in turn fix nitrogen from
the atmosphere, which is taken up by the plant. This
association is extremely valuable as the reduction of
atmospheric dinitrogen into ammonia is second only to
photosynthesis as the most important biological process
on earth (Sylvia et al., 2005). Biological fixation of
nitrogen is also the leading form of global annual
nitrogen input (Russelle, 2008).
Legumes are a major part of the human diet globally
and closely follow the Gramineae in their importance to
humans. The main uses of legumes are as food grains/
seeds, livestock forage, silage and green manure (Jensen
et al., 2012). The well-known legumes include clover,
alfalfa, beans, pea, lentils, mesquite, soybeans, peanuts
(groundnuts), lupins, wisteria and tamarind. Legumes,
especially soybean and peanut, are predominantly used
for the production of vegetable oil. The global harvested
area under legumes is around one tenth of the cereal
crops, and a high proportion of the legumes are grown
in rainfed, low-input systems as compared to cereal
crops. Thus, the average global yield of pulses is only
about one-quarter the average yield of cereal crops
(Akibode & Maredia, 2011).