Ground-level ozone concentrations are high in many crop-growing areas of the world. Concentrations are increasing rapidly in developing countries and are predicted to continue to increase in coming decades unless measures are taken to cut precursor emissions. Ozone pollution has adverse impacts on crop production of sensitive species such as beans, soybean, wheat, rice and maize, and therefore contributes to the yield gap reported for these crops. The study reviewed the literature for field-based evidence of impacts of ambient ozone levels on crops in ODA countries. For most ODA countries, little to no field-based evidence has been collated for ozone impacts on crops. Data is especially lacking for Africa (although some evidence is presented here for Egypt), most of Central and South America and South-eastern and Eastern Europe, Caucasus and Central Asia. However, in the last 15 years, considerable evidence of ozone impacts on crops has emerged from a limited number of locations in China, India and to some extent Pakistan. The reduction of crop yield losses due to ozone in these countries is often in the range of 5 – 20%, with sometimes losses being reported in excess of 40%. The sensitivity to ozone varies between crop species, with legumes such as bean and soybean often being identified as very sensitive, wheat being sensitive and rice and maize being less sensitive to ozone. In addition, the sensitivity to ozone varies between varieties of crop species. There is a need to include assessment of ozone sensitivity in crop breeding programmes and field trials to develop high yielding ozone tolerant varieties that are also more resilient to future climate stresses such as heat and drought stress. In addition, potential crop management options that could contribute to reducing the adverse impacts of ozone on crops should be tested under field conditions. These approaches will contribute significantly to reducing the current yield gap for crops.
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