The Role of Plant Breeding and Biotechnology in Meeting the Challenge of Global Warming

Abstract

The availability of water is already a major limitation for plant production in many parts of the world and shortages of water are recognised as major threats to food security. Drought is often, although not always, accompanied by high temperatures and although these two stresses provoke different responses in plants the dividing line is often blurred as one stress exacerbates the effects of the other. While both drought and heat stress are already problems, the range over which they impact seriously on crop yields and the frequency with which they do it are both predicted to increase as a result of global warming. Plants will also have to cope with a steeply rising atmospheric CO2 concentration. If the predictions of climate change are correct, global warming will cause changes in temperature at a rate unmatched by any temperature change over the last 50 million years. For example, the temperature changes that happened between ice ages and warm interglacial periods as a result of the glacial cycles of the past million years were of 4 to 7 °C (Solomon et al., 2007). Although these changes in temperature were large, they occurred relatively gradually, with the global warming at the end of each ice age taking approximately 5,000 years (Solomon et al., 2007). The current rate of global climate change is much more rapid. The upper end of the range predicted by Global Climate Models in the International Panel for Climate Change (IPCC) 4th Assessment Report is a 5°C increase in global mean temperature by the end of the century. As well as the mean increase in temperature, there is predicted to be an increase in the frequency and severity of extreme weather events. The potential consequences of such events for food production can be seen in the effects of the severe Australian drought of the last decade, which reached crisis point in 2007-2008, and the Russian drought of 2010. Both Australia and Russia are major wheat exporters in normal years, but in 2007-2008 exports of wheat from Australia fell to 1.7 million tonnes, compared with 7.5 million tonnes in 2005-2006, while in July 2010 the Russian government banned wheat exports altogether to protect domestic supply. The price of wheat grain on the London International Financial Futures & Options Exchange (LIFFE) rose in 2008 to 198 pounds (GBP) per tonne. It fell back to below 100 GBP per tonne in 2009 but rose to a new record of 200 GBP per tonne in December 2010. At the time of writing it is at 198 GBP per tonne for July 2011. In both the Australian and Russian droughts, lack of rain was accompanied by high temperature and both stresses would likely have affected grain yield. Drought stress can be