Omics approaches and abiotic stress tolerance in legumes - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 223

well as forage legume species belonging to the Lotus
genus (Pal'ove-Balang et al., 2013). Increased water
stress in the model legume gradually increased levels of
most of the smaller molecules, indicating a progressive,
probably global, reprogramming of the metabolic path-
ways. Unique metabolic responses to drought were also
revealed among different Lotus species, which were
highly conserved, by comparing their metabolomic pro-
files. It is important to note that not all pathways were
conserved among all species. Hence a potent obstacle
to translational approaches was highlighted - these
approaches target the development of traits that are
accompanied by an accumulation of compatible solute
molecules. Also, a comparison between the metabolic
changes induced by drought or salty conditions showed
that the metabolic stress responses studied within each
Lotus species were partially conserved. However, only a
few drought- and salt-responsive metabolites were
common to all of them, including sucrose synthase
involved in nodule formation. The consideration of
these findings can greatly aid in further understanding
water stress physiology of legumes.

2012). Translating the genomic data from sequenced
species to less researched but nonetheless important
'orphan' legumes could enhance the possibilities for
tackling abiotic stress issues.
The growing amount of sequence information when
combined with experimental genomics can revolu-
tionize the way cellular processes and cells are studied.
However, an important question faced by legume
researchers is how advantage should be taken of this
'next generation' opportunity. The fact that a massive
amount of data is now available does not mean the
potential exists to solve all legume problems; 'mega
data' cannot be a universal remedy (Doyle, 2013). The
analysis of this data alongside its incorporation into the
other omics approaches may prove to be a potent tool in
tackling the abiotic stress susceptibility of legumes.
The genomics approach involves developing molec-
ular markers so that the analysis of genetic diversity
can be carried out. This also enables the manipulation
of quantitative trait loci (QTL) through application of
marker-assisted selection (MAS) and hence improve-
ment of the cultivars. DNA regions, also referred to as
molecular markers, can be identified that are strongly
linked to genes related to stress responses and hence
facilitate the development of modified breeding strat-
egies (Yan et al., 2004). These strategies can then be
employed to enhance crop improvement, especially as
far as stress tolerance is concerned.

13.6 Genomics

Genomics is the study of the structure, function, evolu-
tion and mapping of an organism's genome. Hence it
involves intensive efforts to determine the complete
DNA sequence and fine-scale genetic mapping of the
genome of an organism (Marko, 2013). The research
carried out on a single gene cannot be classified as a
genomics study unless the aim of the information gath-
ered regarding genetic pathways and functional
mechanisms is to decipher the gene's effect on the entire
genome structure.
The first legume nuclear genome sequence appeared
only fairly recently, and was undoubtedly fuelled by the
emergence of NGS in the latter half of the 2000s. Owing
to this, there is now a large trove of genomic and tran-
scriptomic data driving a revolution in the world of
biology similar in significance to the previous molecular
revolution.
Genome sequencing of the model legumes Medicago
trunculata and Lotus japonicus along with Glycine max
(soybean) has been completed. Comparison of these
legume genomes has revealed a key role in crop
improvement and stress adaptation (Young & Bharti,

13.6.1 Chickpea
The genomics approach can be applied to develop
climate-resilient chickpea crops. High-throughput geno-
typing technologies along with modern breeding
technologies (e.g. MAS and genomic selection) can aid
in the cause. The efforts of the International Crops
Research Institute for the Semi-Arid Tropics (ICRISAT)
and partner institutes have yielded a great quantity of
genomic resources for the chickpea crop, including
single nucleotide polymorphism (SNP) markers, simple
sequence repeats (SSRs), high-density genetic maps,
diversity array technology (DArT), genome sequences
and transcriptome assemblies. These resources have
been used on various mapping populations to identify
molecular markers that play a role in tolerance to
salinity, drought and heat in chickpea. These approaches
have been used to enhance stress tolerance, and in some
cases, lines with up to 22% increase in yield have been
developed (Varshney & Kudapa, 2013).