International Cooperation

International and regional cooperative agricultural research has historically been an example, par excellence, of the open source approach to biological research. Beginning in the 1950s, and especially in the 1960s, a looming global food crisis led to the development of a group of international agricultural research centres with a specific mandate to foster international exchange and crop improvement relevant to many countries.

This formalization of global biological commons in genetic resources was implemented through an elaborate system of international nurseries with a breeding hub, free sharing of germplasm, collaboration in information collection, the development of human resources, and an international collaborative network (Lantican et al., 2005; Reynolds and Borlaug, 2006; Dixon et al., 2007). The international crop improvement networks implemented by the International Maize and Wheat Improvement Center (CIMMYT) and the International Rice Research Institute (IRRI), and evaluation networks prevalent throughout the USA, Canada and Australia operate an open source system in practice and have impacts on world poverty and hunger. The open source approach is just as relevant today, as witnessed by current crises in food prices and looming crop disease problems of global significance (Byerlee and Dubin, 2008).

Multi-environment trials and managed stress screens: tools for assessing crop adaptation

Modern crop cultivars developed by seed companies, international crop research centres and large national breeding programmes often exhibit very wide geographical adaptation, as well as broad adaptation to the range of environmental and management conditions that occur within a target population of environments (TPE). For example the popular rice varieties 'Swarna' and IR64 are each grown on many millions of hectares in several Asian countries, and the maize inbred line CML312 has contributed to hybrids throughout the Latin American and African subtropics. For wheat, megavarieties have existed since wheat breeding started. Kharkov and Kubanka occupied one-third of the USA wheat area after introduction in early 1900. Cultivars that spearheaded the Green Revolution such as 'Siete Cerros' (also named 'Mexipak' and 'Kalyansona') were grown on millions of hectares from North Africa to South Asia. Selections from the CIMMYT cross 'Veery' were released in more than 40 countries

(Skovmand et al., 1997). The Russian winter wheat Bezostaya dominated in Eastern Europe and West Asia. This breadth of adaptation has been achieved in different ways by different breeding programmes, but the most important tool has been the extensive field testing of experimental breeding lines in many environments during the selection process. Increases in tolerance to a range of stresses such as drought, low fertility and cold in US Corn Belt maize, for example, have contributed greatly to yield gains (Castleberry et al., 1984; Duvick, 1997; Tollenaar et al., 2000) but have not resulted from direct selection for any of these stresses. Rather, they have resulted mainly from the broad-scale multi-location hybrid testing programmes of commercial maize breeding companies that effectively sample conditions occurring in farmers' fields.

Modern commercial breeding programmes, and a few public-sector programmes, evaluate new cultivars in trials sampling their TPE over hundreds of locations and several years. With such extensive testing, the odds are good that some sites will be affected by drought, flooding and heat, and can be used to characterize culti-vars for these stresses. However, multienvironment trials (METs) are also expensive and complex to conduct, and have been implemented on a scale that could provide predictive information for cultivar adaptation to climate change in only a few public and commercial breeding programmes. Small breeding programmes serving local markets often have no access to METs, sampling a wide range of related environments outside their jurisdiction, some of which may not be immediately relevant but may be useful in predicting responses to climate change. Better access to information on cultivar performance in broad-scale multi-location METs could help local and regional breeding programmes speed up their adaptation to climate change.

METs, however, are not the only selection tools that have been used to achieve tolerance to a broad range of stresses. Shuttle breeding in the CIMMYT wheat breeding programme (Trethowan et al., 2007), selection in both the wet and the dry seasons in the IRRI irrigated rice breeding programme (Wassmann et al., 2009a), and managed drought screening in maize, wheat and rice have all contributed to the development of more stress-tolerant cultivars (Banziger et al., 2006). All of these techniques, and more extensive sharing of information and well-characterized germplasm, are key tools that will be needed to allow rapid adaptation to a changing climate.

Compared to maize and rice, the wider natural adaptation of wheat can be attributed to the combination of multiple alleles of photoperiod and chilling (or 'vernalization') sensitive genes that determine the crop's agroecological productivity from high latitudes to equatorial highlands. Spring wheats developed by CIMMYT and its predecessor organizations, that have made impacts since the Green Revolution, were photoperiod-insensitive, a prerequisite for geographic wide adaptation. The breeding system used to develop such germplasm consisted of shuttling alternating generations of wheat between two contrasting north-to-south environments in Mexico -the Yaqui Valley (Ciudad Obregon, Sonora) where days are short during the 'winter cycle' and where photo-insensitivity is required for earlier flowering to avoid terminal heat stresses, and Toluca (Estado de Mexico) with longer days and cool nights. This shuttle was the foundation of the success of what we know today as the Green Revolution wheats, whose main output was a completely new kind of wheat: semi-dwarf, high yielding, insensitive to photoperiod and disease resistant (Trethowan et al., 2007).

The second important component for success of the shuttle is the multi-environment testing of lines selected under the scheme. Every year, several hundred new wheat lines are sent to around 200 cooperators in more than 50 countries, who evaluate the material and share the results with the international wheat community. Without this International Wheat Improvement Network (IWIN), in which basically every major wheat programme worldwide participates, and which is based on germplasm and information exchange between CIMMYT and cooperators (the International Center for Agriculture in Dry Areas (ICARDA) uses a similar system) it is unlikely that wheat developed in Mexico would have had a global impact on wheat improvement. Extensive reviews of the impact from CIMMYT wheat germplasm have been conducted by Lantican et al. (2005) and Reynolds and Borlaug (2006). The information on the performance of the wheat lines in international nurseries obtained through IWIN is paramount for the crossing plan at CIMMYT. Using parents that performed well across a wide range of environments allowed increases in the frequency of desirable alleles in CIMMYT germplasm and is the basis for the high and stable yield.

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