Biotechnology approaches to overcome biotic and abiotic stress constraints in legumes - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 259

the antimicrobial activities of various metabolites in
response to a microbial attack.
These biotechnology approaches have, thus, helped
in the provision of significant benefits to farmers and
the overall agriculture sector. The improvements in
yield and quality of the crops have been directly related
to the incorporation of the molecular sciences into the
legume fields.

proteins produced thereby. Additionally, a number of
resistance genes are not naturally available in the
botanical gene pool. Hence, for the development, intro-
duction and evaluation of the effects of the foreign/
synthetic gene introduced into the plants, a longer
duration and a large number of experimental trials are
necessary before the gene can be introduced into the
agricultural system.
The success of molecular techniques depends greatly
upon the frequency of crossing, generation times and
the employment of manipulative techniques for
improving yields. Therefore, they fail to exhibit any
beneficial effects in cases where the plants show
restrained breeding habits, longer life cycles and vegeta-
tive propagation techniques are frequently employed.
Physical stress factors involve responses that are poly-
genic traits; i.e. a number of plant defence mechanisms
are activated. Hence, prior to the incorporation of resis-
tance genes against these traits, complex screening
procedures may be required to ensure the ideal response
against the threat. Moreover, a number of concerns
have been raised against the adoption of biotechnology
procedures by environmental, regulatory and public
health authorities. Use of genetically modified organisms
(GMOs) for pest control purposes have been the centre
of discussion for years. The introduction of GMOs to the
open field setting can threaten the overall biological
cycle, resulting in the disturbance of food chains and
ecological cycles.
However, the recent advances in biotechnology can
help in reassuring decision makers that it can serve as a
safer alternative to meet the food and energy demands
of the world. The threats associated with the use of
GM crops are mainly based upon hoax and unsound
knowledge about the actual biotechnological tech-
niques. A simple, yet comprehensive, educational
scheme should be devised to educate the masses about
the benefits of employing biotechnology methods for
legumes. This would involve a combined effort by the
agriculture sector, academia and industry. This would
not only promote the acceptance of biotech methods
by the general public but also help in establishing
linkages for evaluating, studying and addressing new
problems in legume agriculture. One of the main
limiting factors in the employment and incorporation
of biotechnology procedures in agriculture is the avail-
ability of resistance genes that can serve in the generation
of effective stress responses. Consequently, only the

15.8 Integration of GM legumes in
current agricultural systems

The most effective biotechnological advance is the
incorporation of disease resistance genes into the plant
genome. This strategy has advantages for plant bio-
technologists as it is effective in providing disease
control, is inexpensive, heritable and environmentally
safe. The technique utilizes the isolation of genes that
may be overexpressed by certain plants in response to
a biotic or abiotic stress condition. Referred to as the
hypersensitive reaction, the response of the plants
involves the release of certain phytochemicals that
work in collaboration to detoxify the threat or neu-
tralize the agents attacking the plant. Glucanases,
chitinases, phytoalexins and protease inhibitors are the
chief species released by the plants to neutralize the
infectious agents. At the cellular level, the response to
the stress factor necessarily involves the alteration of
membrane integrity and the production of reactive
oxygen species. However, the overall morphological,
anatomical and physiological response varies widely
among the taxonomically diverse plants. The resistance
to various stresses and the degree to which a plant
tolerates a stress is markedly different among different
families and species. Lateral transfer of resistance
from one species to another is very rare. Hence, bio-
technology is the only means of transmitting these
characteristics. Resistance to various factors is only
expressed when there is exposure to the causative
agent. Moreover, there are good chances of acceptance
of the foreign disease resistance gene.
However, a number of concerns have been raised
regarding the incorporation of biotechnological proce-
dures into mainstream agricultural processes. In the
case of biotic stress factors, when a single disease resis-
tance gene is introduced into a plant species, many
pathogenic organisms may become resistant to the