The first step in breeding crops with improved response to water and temperature stress is identification of genetic variability governing the plant response. This response may be environment specific and its genetic control is likely to be complex. Soil type and associated water holding capacity and infiltration rates, crop management practices, timing of water stress during the plant growth cycle, temperature and biotic constraints will all influence plant response to drought. Determination of the dominant stress patterns in the target environment is of critical importance if the appropriate genetic variability is to be identified and used in crossing. Chapman et al. (2003) used the concept of 'target population of environments' (TPE) to identify dominant environment types in space and time. Historic weather data, genotype performance in multi-environment trials (METs) and crop distribution information can be used to determine the frequency of occurrence of defined stresses (Edmeades et al. 2006). Once these are known, weighting can be given to those locations representing the TPE in any MET analysis, thereby improving the breeder's selection of appropriate germplasm. Once the TPE is identified and the underlying environmental constraints understood, it will be possible to select parents representing the genetic variability needed to improve adaptation in the TPE. If climate modeling indicates a change in the dominant stress pattern over the next 10-20 years, the breeder can give weighting to the occurrence of this future TPE in the MET analysis, thereby skewing gene frequency in favor of adaptation to the predicted conditions in the target region. It may be possible to develop managed selection environments that mimic the TPE and further improve the selection response.
Climate predictions for the state of New South Wales in Australia typify the challenges crop breeders face in targeting their long-term breeding objectives. Projections for the year 2030 are that the frequency of drought will increase by 70% in the worst case scenario (decreased rainfall) and decrease by 35% in the best case scenario (increased rainfall) (Hennessy et al. 2004). Given these predictions, it is sensible for a plant breeder to assume that improved drought and heat tolerance will be beneficial in the future production environment. Chapter 3 presents more specific information on expected rates of heat and drought changes in key agricultural regions.
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.