Agriculture consumes 70% of the total freshwater reserves, a renewable but finite resource. Among the challenging objectives of sustainable development, more crop biomass needs to be produced with less water consumed. This is what scientists call increasing ‘water use efficiency’ (WUE) and intensive research is dedicated to the dissection of this complex trait and to the identification of the genes controlling the trait in model and crop species. With some success, via conventional or molecular marker-assisted breeding, and via gene transfer technology. Here are some examples of GM applications, not yet in the fields:

Using water efficiency
 

–- Plants control both water transpiration to the atmosphere and carbon dioxide uptake from the atmosphere via the same openings in the leaves called stomata. The control of stomata density and opening is critical to WUE and some of the key genes involved have been isolated and manipulated to increase the ratio ‘biomass produced / water transpired ‘.(1)

Controlling carbon dioxide
 

–- Carbon dioxide fixation by photosynthesis follows different pathways, with contrasting water use efficiencies. The conversion of less efficient crops to more efficient ones by shifting their photosynthetic type was once considered as a dream but is now actively attempted by a rice research consortium under the umbrella of the International Rice Research Institute (IRRI) in the Philippines.(2)

Protecting soil water
 

–- Water released from the fields to the atmosphere is the sum of the water transpired by the plants and of the water directly evaporated by the soil. It is important to maximize the first portion and to minimize the second, and this ratio depends on the way plants colonize the soil with their roots and cover the soil with their leaves. Genes controlling root and leaf growth and architecture are being isolated and functionally tested in model and crop plants, providing increased yields with limited water loss from the soil.(3)

–

For a broader account on the role of biotechnology in saving water resources, go to: FAO, 2007. Coping with water scarcity in developing countries: what role for agricultural biotechnologies? Background Document to the Conference 14 of the FAO Biotechnology Forum (5-30 March 2007): http//www.fao.org/biotech/C14doc.htm