For over 40 years a collaborative network of publicly funded international wheat scientists has made a significant contribution to food security in the developing world. Thousands of modern wheat varieties (MVs) have been released for use in both favourable and marginal environments on well over 50 million hectares. The yield increases associated with genetic improvement in yield potential and adaptation to biotic and abiotic stresses are well documented. Millions of small-scale farmers in the developing world have benefited. While this so-called ‘Green Revolution’ displaced landraces in favour of more productive MVs, these and other genetic resources, held in trust by international organizations, have been utilized to improve the inherent genetic diversity of modern varieties. Furthermore, the result of increased yields reduced the need to bring natural ecosystems under cultivation, by as much as a billion hectares.
Although international wheat breeding has its origins in the 1940s, recognition of a common scientific basis of agricultural problems worldwide was highlighted by the creation of International Agricultural Research Centres (IARCs) which included the International Maize and Wheat Improvement Centre (CIMMYT) established in 1965. This grew into a larger network called the Consultative Group for International Agricultural Research (CGIAR) now comprising 15 IARCs, including the International Centre for Agricultural Research in the Dry Areas (ICARDA) established in Syria in 1977, another key player in the international wheat and barley breeding network. Two of the major coordination responsibilities of CIMMYT are maintaining the world collection of wheat genetic resources – a public good protected by international treaty – and the facilitation of the International Wheat Nurseries.
After the initial impact of the Green Revolution in high production zones through exploitation of Rht-B1 and Rht-D1 dwarfing genes in conjunction with disease resistance, international breeding encompassed more challenging environments through, for example, international shuttle breeding between Brazil and Mexico to overcome problems associated with acid soils that restricted adoption of MVs. Another example is drought, which affects at least 30 million ha of wheat in the developing world. The approach focused initially on exploiting the inherent yield potential and disease resistance of MVs and later combined this with new stress-adaptive traits from wild wheat ancestors through wide crossing techniques. Adoption of modern varieties has increased substantially in drier areas between 1990 and 1997. In all environments, possibly the greatest threat to productivity is disease, especially those caused by fungal pathogens. International wheat breeding has placed great emphasis on genetic control of disease since resource-poor farmers generally lack the means to control diseases chemically.
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