Biotechnology provides a range of new tools and techniques that can provide increased flexibility and efficiency to plant breeders. Some of the most promising targets are described in Table 12.9.
Despite climate change, breeders will be able to respond more rapidly to the requirements of cropping systems. Improvements in conventional breeding are already being realized by many programmes through the application of molecular markers, the use of doubled haploids and a greater understanding of genetic diversity available for plant improvement (see Reynolds et al., Chapter 5; Braun et al., Chapter 7, this volume). Through climate change the environments being targeted by breeders will also shift resulting in changes in the disease and pest spectrum being faced by farmers and in a direct reduction in the stability of yield through adverse climate, such as increased frequency of drought.
In addition to the direct impact of climate change, the community is also expecting agriculture to address production inefficiencies, such as high fuel, fertilizer, pesticide and fungicide applications. In many cases, these represent new targets for breeders but they can be rapidly addressed through the application of new molecular techniques.
Genetic engineering or modification offers a means to accelerate plant improvement and to access diversity not available within the crossable gene pool for many crop species. Where farmers have access to GM technology, extremely rapid adoption has resulted in clear benefits to both the producer and the environment. However, limited consumer acceptance of GM, particularly in Europe, has limited access to the technology and led to high regulatory costs.
Climate change-related problem
Methods to ameliorate effects of climate change
Plants will be exposed to greater extremes in conditions
Water supply may become limited or more variable
Higher temperatures are likely
Drought tolerance and yield under water-limited conditions
Increasing soil salination from coastal salt water inundation, reduced rainfall and increased irrigation
Fertilizer use and production emits 1.2% of the world's greenhouse gases (Wood and Cowie, 2004); N fertilizer production consumes ten times more energy than other fertilizers (Lal, 2004)
Disease infection and pest infestations may increase
Gene sequences have been identified that determine flowering time for many crops. Rapid 'fine tuning' of crop phenology and life cycle duration can maximize yield under diverse climatic conditions
Omic analyses have enabled better understanding of regulatory networks controlling plant responses to limited water supply. Functional genomics has also enabled the identification of genes regulating drought responses
Yields increase with temperature up to a critical threshold and then decline sharply. Climate change is predicted to increase the likelihood of heat stress in many cropping regions
Identification of gene sequences and quantitative trait loci controlling Na+ exclusion and tissue tolerance
Crops only recover around 50% of N supplied (Eickhout et al., 2006). Identification of gene sequences controlling N-use efficiency has led to more fertilizer-efficient rice (Shrawat et al., 2008)
The dependence of pest and disease dynamics upon prevailing temperature and rainfall profiles makes future pest and disease outbreaks notoriously difficult to predict (Gregory et al., 2009). Breeders may not be able to keep pace with changes
Match plant development to availability of radiation, water and nutrient resources. Minimize exposure to climatic extremes at critical developmental stages (Craufurd and Wheeler, 2009)
Tailor molecular drought response regulators to engineer water-use efficient and drought-tolerant crops. Modify drought tolerance according to the time of onset of water constraints
Identify physiological mechanisms and associated molecular markers for application in crop breeding programmes. Advances in stress/trait dissection and rapid phenotyping will enhance the understanding of the physiological and genetic bases of heat tolerance
Select for salt tolerance using direct phenotyping or molecular markers. Engineer cell-specific Na+ exclusion using identified gene sequences as a more efficient strategy for salt-tolerant crop development (M0ller et al., 2009)
Transfer N-use efficiency gene sequences to other major crop species, including maize and wheat, as a major target for commercial plant breeding (Arcadia, 2009)
Manipulate levels of existing anti-pathogen or pest compounds (Delaunois et al., 2009; Hexima, 2009) or, through using novel biotechnology strategies (Nolke et al., 2004), identify novel pathogens and monitoring pathogen spread (Park, 2008)
The high costs have virtually eliminated the public sector's ability to deploy GM technologies and have restricted the types of traits and the crops in use. However, there are signs in several countries that community attitudes to this technology are changing, particularly with respect to the use of GM crops to improve tolerance to environmental stresses.
The combination of new methods in plant breeding, including MAS as well as the opportunities provided by GM crops, increase both the speed and the flexibility of crop improvement. However, relatively few breeding programmes have had the regulatory framework, skills, background information and technology access needed to deploy these methods. These limitations remain the major impediment to the widespread use of biotechnology and they will only be addressed through strong international collaboration and capacity building.
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