Biotechnology approaches to overcome biotic and abiotic stress constraints in legumes - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 255

Table 15.2 Genetically modiied legumes and the genes
manipulated for enhancing abiotic stress resistance.

of legume quality, in terms of better wood, nutritional
content and nitrogen fixation capability (Chandra et al.,
2010; Pratap et al., 2010; Provorov, 2013). Incorporation
of pest resistance genes into legumes helps enhance
tolerance to pests, thereby decreasing the need to
employ various pesticides (Keneni et al., 2011).
Additionally, the introduction of virus resistance genetic
cassettes has helped in the control of not only viral
diseases but also insect vectors that are involved in the
transmission of plant viruses (Cavatorta et al., 2012).
However, the main focus of biotechnologists has now
shifted from the control of biotic to abiotic stress factors.
Biological threats cause the activation of only a single
genetic pathway for the induction of disease. In
comparison, physical stress factors are involved in the
induction of a series of events that together result in
detrimental effects on the plant. Therefore, the intro-
duction of genes that can provide resistance against
these abiotic stress factors is the main target of biotech-
nological intervention. Genes encoding factors involved
in the defence against drought, extremes in tempera-
tures and salinity have been successfully incorporated
into a number of leguminous plants (Thao & Tran,
2012). These have resulted in the achievement of bene-
fits, both in the quality and overall agricultural yield of
legumes.

Legume species Genes isolated References

Glycine max DRE-binding protein

(drought tolerance)

Chen et al. (2007)

Vicia faba PR10a (cold tolerance) Hanafy et al. (2013)

Arachis hypogaea PnAG3 (drought resistance) Yu et al. (2012)

Phaseolus mungo Dn2 (aphid resistance) Priya et al. (2013)

the diagnosis of an aetiological agent to the final
development of a solution for the diseased condition,
the dedication of a number of scientists is required.
Plant pathologists, geologists, chemists, geneticists,
molecular biologists, biotechnologists, microbiologists,
bioinformaticians and ecologists, all are necessary for
the development of a successful remedy for a disease
condition. The discovery of a pathological condition,
determination of aetiological factors and the players
involved in mounting a response to the stress factors,
and ultimately the employment of interventional strat-
egies - all contribute to the introduction or enhancement
of legumes' defences against physical and biological
constraints. Molecular interventional strategies have
helped in the attainment of tolerance against cold stress,
herbicides, drought, salinity and high-intensity light.
Moreover, these strategies have aided in the provision
of resistance against viruses, bacteria, fungi and other
parasites. Transgenic plants encoding genes for the
enhanced production of osmoprotectants, enzymes and
secondary metabolites have helped legumes in attaining
stress resistance (Table 15.2).

15.7 Molecular approaches to
improving legume defences

The advent of modern biotechnological procedures has
helped in the incorporation of better protective strat-
egies against biological and physical stress factors. The
molecular intervention strategies are based upon an
understanding of various disease and stress conditions.
The molecular and cellular mechanisms involved are
investigated, followed by isolation of the factors involved
in mounting a response to these conditions. These
genetic and molecular entities are then introduced into
the target plants, which are then evaluated for their
ability to cope with a stress condition (Table 15.3).

15.6.2 Benefits obtained by biotechnology
approaches
A human population explosion over the past four
decades has added to the demand for both food and cash
crops. Increased nutritional demand, a growing need to
supply raw materials for industrial processes and a
decreased land area for agricultural purposes have all
contributed to the acceptance by the public of alternative
methods for crop yield improvement. Biotechnology
has provided innovative ideas and methods to deal with
many of the severe stress conditions that would not
have been targeted by any traditional means of crop
improvement (Hohn & Schachermayr, 2010). These
molecular techniques have helped in the improvement

15.7.1 Incorporation of disease
resistance genes
A basic stage in developing ways of dealing with the
biotic stress factors is gaining an understanding of the
disease pathogenesis. Many bacterial and fungal species