Climate change in Australia is expected to influence crop growing conditions through direct increases in elevated carbon dioxide (CO2) and average temperature, and through increases in the variability of climate, with potential to increase the occurrence of abiotic stresses such as heat, drought, waterlogging, and salinity. Associated effects of climate change and higherCO(2) concentrations include impacts on the water-use efficiency of dryland and irrigated crop production, and potential effects on biosecurity, production, and quality of product via impacts on endemic and introduced pests and diseases, and tolerance to these challenges. Direct adaptation to these changes can occur through changes in crop, farm, and value-chain management and via economically driven, geographic shifts where different production systems operate. Within specific crops, a longer term adaptation is the breeding of new varieties that have an improved performance in 'future' growing conditions compared with existing varieties. In crops, breeding is an appropriate adaptation response where it complements management changes, or when the required management changes are too expensive or impractical. Breeding requires the assessment of genetic diversity for adaptation, and the selection and recombining of genetic resources into new varieties for production systems for projected future climate and atmospheric conditions. As in the past, an essential priority entering into a ` climate-changed' era will be breeding for resistance or tolerance to the effects of existing and new pests and diseases. Hence, research on the potential incidence and intensity of biotic stresses, and the opportunities for breeding solutions, is essential to prioritise investment, as the consequences could be catastrophic. The values of breeding activities to adapt to the five major abiotic effects of climate change (heat, drought, waterlogging, salinity, and elevated CO2) are more difficult to rank, and vary with species and production area, with impacts on both yield and quality of product. Although there is a high likelihood of future increases in atmospheric CO2 concentrations and temperatures across Australia, there is uncertainty about the direction and magnitude of rainfall change, particularly in the northern farming regions. Consequently, the clearest opportunities for ` in-situ' genetic gains for abiotic stresses are in developing better adaptation to higher temperatures (e. g. control of phenological stage durations, and tolerance to stress) and, for C-3 species, in exploiting the (relatively small) fertilisation effects of elevated CO2. For most cultivated plant species, it remains to be demonstrated how much genetic variation exists for these traits and what value can be delivered via commercial varieties. Biotechnology-based breeding technologies (marker-assisted breeding and genetic modification) will be essential to accelerate genetic gain, but their application requires additional investment in the understanding, genetic characterisation, and phenotyping of complex adaptive traits for climate-change conditions.
