Abiotic stress factors are the main limitation to plant growth and yield in agriculture.
Among them, drought stress caused by water deficit, is probably the most impacting
adverse condition and the most widely encountered by plants, not only in crop fields but
also in wild environments. According to published statistics, the percentage of droughtaffected
land area in the world in 2000 was double that of 1970 [1].
Another major environmental factor that limits crop productivity, mainly in arid and semiarid
regions is high salinity. Approximately 19.5% of the irrigated soils in the world have
elevated concentrations of salts either in the soil or in the irrigation water [2], damaging
both the economy and the environment [3, 4]. The deleterious effects of salinity on plant
growth are associated with low osmotic potential of
soil solution (water stress), nutritional
imbalance, specific ion effect (salt stress), or a combination of these factors [5].
Abiotic stress leads to a series of morphological, physiological, biochemical, and molecular
changes that adversely affect plant growth and productivity [6]. Drought, salinity, extreme
temperatures, and oxidative stress are often interconnected, and may induce similar cellular
damage (for more details see [7]).
During the course of its evolution, plants have developed mechanisms to cope with and
adapt to different types of abiotic and biotic stress. Plants face adverse environmental
conditions by regulating specific sets of genes in response to stress signals, which vary
depending on factors such as the severity of stress conditions, other environmental factors,
and the plant species [8].
The sensing of these stresses induces signaling events that activate ion channels, kinase
cascades, production of reactive oxygen species, and accumulation of hormones [9]. These signals ultimately induce expression of specific genes that lead to the assembly of the
overall defense reaction. In contrast to plant resistance to biotic stresses, which is mostly
dependent on monogenic traits, the genetically complex responses to abiotic stresses are
multigenic, and thus more difficult to control and engineer [10].
The conventional breeding programs are being used to integrate genes of interest from inter
crossing genera and species into the crops to induce stress tolerance. However, in many
cases, these conventional breeding methods have failed to provide desirable results [11].
In recent decades, the use of techniques based on in vitro plant tissue culture, has made
possible the development of biotechnological tools for addressing the critical problems of
crop improvement for sustainable agriculture. Among the available biotechnological tools
for crop breeding, genetic engineering based on introgression of genes that are known to be
involved in plant stress response and in vitro selection through the application of selective
pressure in culture conditions, for developing stress tolerant plants, have proved to be the
most effective approaches [12].
On the other hand, it is often difficult to analyze the response of plants to different abiotic
stresses in the field or in greenhouse conditions, due to complex and variable nature of these
stresses. In vitro tissue culture-based tools have also allowed a deeper understanding of the
physiology and biochemistry in plants cultured under adverse environmental conditions
[13].
In this work, the progress made towards the development of abiotic stress-tolerant plants
through tissue culture-based approaches is described. The achievements in the better
understanding of physiological and biochemical changes in plants under in vitro stress
conditions are also reviewed.
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