Integrated genomics, physiology and breeding approaches for improving drought tolerance in crops. Abstract. Drought is one of the most serious production constraint for world agriculture and is projected to worsen with anticipated climate change. Inter- disciplinary scientists have been trying to understand and dissect the mechanisms of plant tolerance to drought stress using a variety of approaches; however, success has been limited. Modern genomics and genetic approaches coupled with advances in precise phenotyping and breeding methodologies are expected to more effectively unravel the genes and metabolic pathways that confer drought tolerance in crops.
CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources 2011 6, No. 032 Review Plant mutation breeding in agriculture Ranjith Pathirana* Address: The New Zealand Institute for Plant and. CR OP SERIES CLEARFIELD* Wheat no. CLEARFIELD* is a production system comprised of an herbicide-tolerant wheat variety (Above or AP502 CL) and BeyondTM herbicide to. Legume Crops Phylogeny and Genetic Diversity for Science and Breeding.
This article discusses the most recent advances in plant physiology for precision phenotyping of drought response, a vital step before implementing the genetic and molecular- physiological strategies to unravel the complex multilayered drought tolerance mechanism and further exploration using molecular breeding approaches for crop improvement. Emphasis has been given to molecular dissection of drought tolerance by QTL or gene discovery through linkage and association mapping, QTL cloning, candidate gene identification, transcriptomics and functional genomics. Molecular breeding approaches such as marker- assisted backcrossing, marker- assisted recurrent selection and genome- wide selection have been suggested to be integrated in crop improvement strategies to develop drought- tolerant cultivars that will enhance food security in the context of a changing and more variable climate. Introduction. Drought is the most devastating abiotic stress affecting crop productivity, which is caused by insufficient rainfall and/or altered precipitation patterns (Toker et al. The seriousness of drought stress depends on its timing, duration and intensity (Serraj et al.
The impact of drought on crop production has been evidenced as early as the beginning of the seventeenth century, known as “Sahel drought”, caused due to human intervention effects of deforestation, overgrazing and industrialization (Held et al. Increase in greenhouse emissions has resulted in altered precipitation, increase in arid land, desertification and finally reduction in crop productivity. Moreover, it has been causing global warming, which in turn is responsible for raising the earth’s surface temperature and sea water level. As of today, climate–yield predictions are well captured in several important major crop species through simulations (Lobell et al. These important crops are in need of adaptation investments to avoid catastrophic yield losses and to meet the food demand of a fast- increasing population. Drought is often accompanied by relatively high temperatures, which promote evapotranspiration and affects photosynthetic kinetics, thus intensifying the effects of drought and further reducing crop yields. It is anticipated that the occurrence of drought in many food- producing regions will increase significantly in response to climate change (Collins et al.
Reynolds and Ortiz 2. Tolerance to drought is a complex quantitative trait controlled by several small effect genes or QTLs and is often confounded by differences in plants phenology (Barnabas et al. To address the complexity of plant responses to drought, it is vital to understand the physiological and genetic basis of this response. Failure to understand the molecular mechanisms of seed yield stability has hampered both traditional breeding and the use of modern genetics in the improvement of drought tolerance of crop plants (Passioura 2. Sinclair 2. 01. 1). Recent advances in crop physiology, systematic plant phenotyping and genomics have led to new insights in drought tolerance, thus providing crop breeders with greater knowledge of the gene networks and providing new tools for plant improvement to increase crop yield (Tuberosa and Salvi 2.
While plant physiology improves our understanding of the complex network of drought tolerance- related traits thus improving selection efficiency, molecular biology and genomics approaches identify the candidate genes and quantitative trait loci (QTLs) associated with these traits. While QTLs can be deployed in crop improvement through molecular breeding, candidate genes are the prime targets for generating transgenics using genetic engineering (Varshney et al. Identification of the “most appropriate” candidate genes along with selection of “most suitable promoters” and generation of a large number of events are critical for the development of desirable transgenics with enhanced drought tolerance using know- how knowledge (http: //www. Luo 2. 01. 0; Varshney et al.
- Union of Concerned Scientists. Evaluating the Performance of Genetically Engineered Crops.
- Integrated genomics, physiology and breeding approaches for improving drought tolerance in crops.
- Plant breeding started with sedentary agriculture and particularly the domestication of the first agricultural plants, a practice which is estimated to date back 9,000 to 11,000 years. Initially early farmers simply selected.
- ISB NEWS REPORT JULY 2013 Current Developments of Intragenic and Cisgenic Crops Inger B
- Biofortification is the development of micronutrient-dense staple crops using the best traditional breeding practices and modern biotechnology. This approach has multiple advantages.
However, the expensive regulatory process and negative public perceptions of biosafety limit the application of genetic engineering approach, while there is a wider acceptance of products generated through molecular breeding (Vogel 2. Farre et al. 2. 01. Targetted Induced Local Lesions in Genome (TILLING) (see Barkley and Wang 2. In the last decade, several important reviews of plant drought response and tolerance have been published (http: //www. Recent. The importance of multifaceted strategies including genetic engineering (Bhatnagar- Mathur et al.
Woody perennial plants, including trees that produce fruits and nuts of horticultural value, typically have long breeding cycles, and development and introduction of improved cultivars by plant breeders may require many.
Sinclair 2. 01. 1) and genomics approaches (Tuberosa and Salvi 2. Cattivelli et al. Ashraf 2. 01. 0; Varshney et al. Leung 2. 00. 8; Bernier et al. Fleury et al. 2. 01. Manavalan et al. 2.
Yadav et al. 2. 01. Wan et al. Also, the descriptions of molecular- physiological mechanisms of drought tolerance were outlined by several reviews (Bartels and Sunkar 2.
Maggio et al. 2. 00. Charron and Quatrano 2. In this review, we highlight the importance of drought tolerance, especially in a variable climate and discuss the recent progress made in the area of crop physiology for precise phenotyping and genomic approaches, such as identification and cloning of QTLs and identification of candidate genes associated with drought tolerance. In addition, new molecular breeding strategies such as marker- assisted recurrent selection (MARS) and genomic selection (GS) or genome- wide selection (GWS) are discussed as options to be integrated in crop improvement programmes for developing the next generation of drought- tolerant crops.
The increasing importance of drought tolerance in variable climates. The global water shortage caused by an increasing world population and worldwide climate change is considered as one of the major challenges facing agriculture today. The combination of continued impact of drought and high temperature impairs the photosynthesis during the day- time and increases the surface temperatures in the night, which in turn increase the photorespiratory losses and thus the productivity. The elevated greenhouse gas concentrations may lead to the general drying of the subtropics by the end of this century, thus creating widespread drought stress in agriculture . This shortage of water may threaten sustainable crop farming, since agricultural activities account for 7. UNEP 2. 00. 9; Yang et al. It is also anticipated that by 2.
Reynolds and Ortiz 2. In brief, the convergence of population growth and variable climate is expected to threaten food security on a worldwide scale. Relatively inexpensive and easier to adapt methods would be to switch crops or altering planting seasons according to predicted precipitation patterns and continued expansion of irrigation. However, worldwide occurrence of drought has become endemic due to climate change. This raises serious concerns and places huge responsibilities on the shoulders of scientists for developing “drought- suited varieties” through molecular breeding and genetically modified approaches.
However, it is clear that the demand to produce sufficient major food crops (wheat, rice and maize) for the growing population has always been increasing. Hence, optimizing yield stability for these major crops and locally important crops is essential. Therefore, maintaining food security in this scenario will require systematic approaches (see later) including the use of drought- tolerant germplasm (Reynolds and Ortiz 2. Recent advances in plant physiology, genomics and some future breeding strategies (Fig. A holistic approach for integrating genomics, physiology and breeding approaches for developing the superior varieties with enhanced drought tolerance. Addressing the complexity of plant response to drought. Among the various abiotic stresses that curtail crop productivity, drought is the most recalcitrant to breeding (Tuberosa and Salvi 2.
In the past, drought tolerance breeding has been hindered by the quantitative inheritance of the trait and our poor understanding of the physiological basis of yield in water- limited conditions (Sinclair 2. The physiological dissection of complex traits like drought is a first step to understand the genetic control of tolerance and will ultimately enhance the efficiency of molecular breeding strategies. Developing and integrating a gene- to- phenotype concept in crop improvement requires particular attention to phenotyping and ecophysiological modelling, as well as the identification of stable candidate genomic regions through novel concepts of . Knowledge of both the plant physiological response and integrative modelling are needed to tackle the confounding effects associated with environment and gene interaction (Tardieu and Tuberosa 2.
To maximize the impact of using specific traits, breeding strategies requires a detailed knowledge of the environment where the crop is grown, genotype . A physiological approach has an advantage over empirical breeding for yield per se because it increases the probability of crosses resulting in additive gene action for stress adaptation, provided that the germplasm is characterized more thoroughly than for yield alone (Reynolds and Trethowan 2. Criteria for using physiological traits in breeding programmes.