Delivering drought tolerance to those who need it: from genetic resource to cultivar
R. M. TrethowanUniversity of Sydney, Plant Breeding Institute, 107 Cobbitty Road, Cobbitty, NSW, Australia. Email: richard.trethowan@sydney.edu.au
Crop and Pasture Science 65(7) 645-654 https://doi.org/10.1071/CP13401
Submitted: 19 November 2013 Accepted: 28 April 2014 Published: 15 July 2014
Abstract
Drought limits crop yields, and with climate change, the severity of water stress is projected to increase in many production environments. Therefore, it has never been more important to deliver the findings of drought research to farmers. The maintenance in situ, collection and characterisation of key genetic variability for stress tolerance, its introgression into agronomically adapted materials, and the subsequent deployment of improved cultivars is a continuum. This paper focuses on one segment of the pathway—the process from genetic characterisation to cultivar delivery—and possible efficiencies are discussed with emphasis on wheat, one of the world’s most important food crops.
The first efficiency is to limit the initial exploitation of genetic resources to close relatives, as much of this variation remains uncharacterised, rather than attempting gene transfers from unrelated species, which is time-consuming and has a low probability of success. Synthetic wheat, developed by crossing modern tetraploid wheat to Aegilops tauschii, the donor of the D-genome, has provided new genetic diversity for stress tolerance and yield advantages under drought in excess of 30% have been reported. Synthetic wheat can also be made using Triticum dicoccum, often referred to as emmer wheat, thus introducing new variation for all three wheat genomes.
The second efficiency is better coordinated, field-based phenotyping. The Australian Managed Environment Facility and similar national facilities established in India and China provide a basis for accurate field-based phenotyping and the weighting of physiological traits related to water-use efficiency on a national scale. The calculation of a water balance, careful management of site heterogeneity and judicious use of rain shelters maximise trait expression and improve the relevance of results.
The third efficiency is to maximise locally the benefits of global public-good research. The global wheat improvement programs of the Consultative Group on International Agricultural Research (CGIAR) have a mandate to ‘tame’ genetic diversity and distribute these improved materials globally in nurseries targeted to specific environmental conditions such as drought. Nevertheless, the exploitation of these materials is rarely managed well at the national level. The CIMMYT Australia ICARDA Germplasm Evaluation (CAIGE) program is a nationally coordinated germplasm introduction and evaluation program. Key CGIAR nurseries are received and grown by Australian quarantine, increased at one or two locations, tested for disease resistance and subsequently grown nationally in yield trials. The data are stored on the CAIGE website and, along with all supporting data generated by the international centres, are publicly available.
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