Peanut (Arachis hypogaea L.) is one of the economically important oil and
food crops. Peanut is generally grown across a wide range of environments
including rain-fed conditions. Because of this, drought is a main limiting
factor to peanut production in the semi-arid areas. The development of
salinity and drought stress-tolerant peanut to exploit the drought-prone and
salinity-affected areas of the world has been imperative these past years.
Now, mannitol may just be the thing that would make it a reality.

Mannitol accumulation in most plants works for the alleviation of salinity
and osmotic-induced stresses. However, it is not naturally synthesized in
peanut. The mtlD gene (from Escherichia coli) codes for an enzyme that
converts fructose 2 with 6-phosphate to mannitol1-phosphate. Peanuts
transformed with mtlD were evaluated for salinity and drought stress
tolerance. The overexpression of the mtlD gene translated to the transgenic
peanuts' improved tolerance to salinity and drought. This was revealed by
better growth and physiological parameters like mannitol content, total
chlorophyll content, and relative water content in transgenic peanuts.

The better performance of the transgenic plants was attributed to the
stress-shielding role of mannitol. However, the mtlD expression causing the
activation of other protective reactions in transgenic peanut may also be
possible.

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