Abstract
By 2050 world population will reach more than 9 x 109 people; to feed them, crop productivity must be quickly boosted,
since at the present rates the increase in food production will not be able to cope with human population growth. The
simplest way to attain this goal is to improve the abiotic stress tolerance of cultivated species. For all important crops, average
yields are only a fraction - between 20% and 50% - of record yields, and these losses are mostly due to drought and high soil
salinity; these adverse environmental conditions will worsen in many regions because of global climate change, increasing in
addition the scarcity of new arable land and of water for irrigation. Neither traditional plant breeding nor genetic engineering
has yet provided commercial stress-tolerant crops - except for a transgenic drought-tolerant maize variety - which is not
surprising considering the complexity of these traits. However, based on several promising lines of research presently in
progress, we should be confident that in the coming years the combination of classical breeding and transgenic approaches
will allow the improvement of abiotic stress tolerance for, at least, some of our major crops. A complementary strategy will
rely on the development of new tolerant crops by domestication of wild plants naturally resistant to stress, halophytes and
xerophytes. Highly salt-tolerant halophytes, for example, could be grown in salinised crop land already lost for agriculture, and
also in naturally saline, marginal soils, using brackish or sea water for irrigation - with the added advantage that they will not
compete for limited resources (good-quality water and fertile crop land) with standard cultivated species. The problem that we
face is serious enough to exploit all available opportunities to increase agricultural productivity in the shortest possible time.
