Exploring Genetic Resources to Increase Adaptation of Wheat to Climate Change
The opinions expressed and arguments employed in this publication are the sole responsibility of the authors and do not necessarily reflect those of the OECD or of the governments of its Member countries.The Special Session was sponsored by the OECD Co-operative Research Programme on Biological Resource Management for Sustainable Agricultural Systems, whose financial support made it possible for most of the invited speakers to participate in the Special Session.
Abstract The combined problems of climate change, population growth, and increased demands on a declining natural resource base force scientists to push crop performance to its limits. A powerful strategy is to explore genetic resources to identify promising material that can be used directly in breeding, for gene discovery, and to further understand the mechanisms of adaptation. Initially traits must be defined for stress targets using conceptual models, examples being better root systems to access subsoil deep water and the ability to store and remobilize water soluble carbohydrates from storage tissue. New sources of diversity for such traits can be found in collections such as the World Wheat Collection housed at CIMMYT; for example, Mexican landraces provide good sources of both of these traits. Being a polyploid, wheat has a useful secondary gene pool that can be used to re-synthesize hexaploid wheat, while transgenic approaches remove all taxonomic limits to plant improvement. To efficiently explore genetic resources, for crop improvement and to identify genetic and mechanistic bases, requires high throughput phenotyping approaches. For example, an airborne remote sensing platforms is used to determine spectral indices associated with temperature, water content, and pigment composition of leaves via thermal and multispectral imagery. Using the above approaches, best lines are used directly in pre-breeding to combine favorable combinations of traits and their alleles. These approaches have already delivered a new generation of drought adapted lines where cumulative gene action on yield is observed through strategic combination of stress adaptive traits many coming from landraces or products of wide crossing with wheat wild relatives.
Keywords Landraces • Physiological breeding • Phenotyping • Remote sensing • Synthetic wheat
The CIMMYT coordinated International Wheat Improvement Network (IWIN) partners with hundreds of wheat breeders worldwide to provide new genotypes (~1,000 annually) to national programs as international public goods, through the following mechanisms (Braun et al. 2010):
• Free exchange of germplasm with all national public and private breeding programs worldwide, including accessions from genetic resource collections.
• Centralized breeding hubs that focus on generic needs – i.e., yield potential, yield stability, genetic resistance to range of biotic and abiotic stresses, consumeroriented quality traits.
• Distribution of international nurseries specifically targeted to a number of major agro-ecosystems, via national wheat programs worldwide.
• Analysis of international yield trials and free access to all data collected.
• Global disease and pest monitoring to ensure relevance of current local, regional, and global breeding activities.
• Capacity building and training of research partners.
• Regular contact among research partners through consultation, workshops, etc., to help identify the latest technology needs.
Through the IWIN, wheat germplasm has spread continually since the Green Revolution and is now not only extremely well represented in farmers fields of the developing world, but is also commonly seen in the pedigrees of wheat lines in developed countries (Braun et al. 2010). The continued effectiveness of these wheat breeding strategies have been demonstrated right up the present with yield data from hundreds of testing sites worldwide showing average genetic yield gains of 1 % every year in germplasm targeted to water limited environments (Manes et al. 2012), and 0.6 % per year in fully irrigated environments (Sharma et al. 2012) based on lines distributed since 1995. Germplasm distributed by IWIN is maintained resistant to the full range of diseases that commonly affect wheat (Braun et al. 2010). As a result, resource poor farmers in LDCs are buffered financially from having to apply expensive fungicide, while the environment is protected from the additional agrochemical burden. An important spin off of the IWIN are massive phenotypic datasets that have allowed breeders to identify germplasm with either specific adaptation to local challenges and diseases, or broad (spatial and/or temporal) adaptation to many locations and cropping systems (e.g., Gourdji et al. 2012).
In spite of this achievement, genetic gains still fall short of meeting the predicted demands by 2050 (Rosegrant and Agcaoili 2010), a mismatch that represents a serious challenge for future food security especially in the light of the challenges associated with climate change. One of the best ways to address this challenge from the point of view of genetic improvement is through a more systematic use of genetic resources in breeding. To achieve this requires a series of steps that are outlined in the rest of this paper.