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Blum A.,PO Box 16246
Functional Plant Biology | Year: 2014

A meta-analysis of 520 reports published during the last 20 years on transgenic and mutant plants generated towards drought resistance revealed a total of at least 487 tested transgenic plants involving at least 100 genes claimed to be functional towards drought resistance. During this period, the rate of reported new experimental transgenic model or crop plants for drought resistance has been increasing exponentially. Despite these numbers, qualified sources of information indicate a very limited impact on global dryland agriculture, whereas the genetically modified (GM) market hardly recognises drought-resistant GM cultivars. This paper discusses possible reasons for the limited impact of genomics on the delivery of drought-resistant cultivars, which are beyond issues of regulation, propriety or commercialisation. These reasons are mainly tied to scientific and methodological problems in drought stress gene expression work and the functional genomics protocols used to identify drought resistance. Insufficient phenotyping of experimental transgenic plants for drought resistance often does not allow true conclusions about the real function of the discovered genes towards drought resistance. The discussion is concluded by proposing an outline of a minimal set of tests that might help us resolve the real function of discovered genes, thus bringing the research results down to earth. © CSIRO 2014.

Contemporary plant breeding is under pressure to improve crop productivity at a rate surpassing past achievements. Different research groups dealing with this issue reached similar conclusions that the solution lies in improved biomass production by way of enhanced light capture and use efficiency, modified photosystem biochemistry, and improved partitioning of assimilates to the economic part of the plant. There seems to be a consensus of sorts. This 'opinion paper' calls attention to the phenomenon of heterosis, as expressed in maize, sorghum, and other crops where, depending on the case and the trait, larger biomass and greater yield have been achieved without a change in growth duration, photosystem biochemistry, or harvest index. This discussion maintains that there is no consensus about the genetics or the genomics of heterosis in regulating yield under diverse environments. Therefore, in a search for the basis of heterosis in yield and adaptation, the discussion bypasses the genetics and searches for answers in the phenomics of heterosis. The heterotic phenotype in itself provides challenging and important hints towards improving the yield of open-pollinated crops in general. These hints are linked to the homeostasis of photosynthesis with respect to temperature, the photobiology of the plant as mediated by phytochrome, the architectural foundations of the formation of a large sink, and the associated hormones and signals in controlling sink differentiation and source-sink communication. This discussion does not lay out plans and protocols but provides clues to explore within and beyond the current thinking about breeding for high yield. © The Author 2013. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions.

Turner N.C.,University of Western Australia | Blum A.,PO Box 16246 | Cakir M.,Murdoch University | Steduto P.,Food and Agriculture Organisation of the United Nations | And 2 more authors.
Functional Plant Biology | Year: 2014

The objective of the InterDrought conferences is to be a platform for debating key issues that are relevant for increasing the yield and yield stability of crops under drought via integrated approaches. InterDrought-IV, held in Perth, Australia, in September 2013, followed previous InterDrought conferences in bringing together researchers in agronomy, soil science, modelling, physiology, biochemistry, molecular biology, genetics and plant breeding. Key themes were (i) maximising water productivity; (ii) maximising dryland crop production; (iii) adaptation to water-limited environments; (iv) plant productivity under drought through effective water capture, improved transpiration efficiency, and growth and yield; and (v) breeding for water-limited environments through variety development, and trait-based genomics-assisted and transgenic approaches. This paper highlights some key issues and presents recommendations for future action. Improved agronomic interventions were recognised as being important contributors to improved dryland crop yields in water-limited environments, and new methods for exploring root architecture and water capture were highlighted. The increase in crop yields under drought through breeding and selection, the development of high-throughput phenotyping facilities for field-grown and pot-grown plants, and advances in understanding the molecular basis of plant responses and resistance to drought stress were recognised. Managed environment phenotyping facilities, a range of field environments, modelling, and genomic molecular tools are being used to select and release drought-resistant cultivars of all major crops. Delegates discussed how individuals and small teams can contribute to progress, and concluded that interdisciplinary research, linkages to international agricultural research centres, public-private partnerships and continuation of the InterDrought conferences will be instrumental for progress. © CSIRO 2014.

Blum A.,PO Box 16246
Cereal Research Communications | Year: 2014

After a decade of genetic manipulation and improvement, triticale stand out as a crop of high biomass and grain yield potential which generally surpass that of wheat. Its high productivity is most likely derived from high rates of carbon assimilation linked to stomatal physiology and probably low respiration rate. Being a derivative of rye, triticale has always been assumed to be relatively resistant to abiotic stress. The last review of triticale adaptation to abiotic stress as published by Jessop (1996) pointed at its general and specific fitness to harsh growing conditions. This review as based on additional data published in the last 20 years indicates that triticale retain good to excellent adaptation to conditions of limited water supply and problem soils which involve salinity, low pH, defined mineral toxicities and deficiencies and waterlogging. Despite the understandable expectations, freezing tolerance of triticale was not found to be up to the level of rye. The freezing tolerance of the rye complement in triticale is inhibited by unknown factors on the wheat parent genome. Any given triticale cultivar or selection cannot be taken a priori as being stress resistant. Research has repeatedly shown that triticale presented large genetic diversity for abiotic stress resistance and most likely this diversity has not yet been fully explored due to the very limited research and the small studied sample of the potential triticale germplasm. Triticale is a valuable stress tolerant cereal on its own accord and a potential genetic resource for breeding winter and spring cereals. Because of its high productivity and resilience it might become as important as wheat or better on a global scale if its grain technological quality will be improved to the level of wheat.

Blum A.,PO Box 16246
Functional Plant Biology | Year: 2011

Drought resistance is being increasingly labelled as being a 'complex trait', especially with the recent expansion of research into its genomics. There is a danger that this label may turn into an axiom that is liable to damage education on the subject as well as research and the delivery of solutions to the farmer. This opinionated review examines whether there is grounds for such an axiom. Drought resistance is labelled as a 'complex trait' mainly when viewed by molecular biologists from the gene discovery platform. This platform is capable of expressing hundreds and thousands of drought-responsive genes, which are up- or down-regulated under dehydration stress according to growth stage, plant organ or even time of day. Sorting out the 'grain out of the chaff' in order to identify the function of the candidate genes towards drought resistance is difficult and, thus, the idea that drought resistance is complex is raised. However, when drought resistance is viewed from the physiological and agronomic whole-plant and crop platform, it appears much simpler; its control, whether constitutive or adaptive, is rather obvious with respect to manipulation in breeding and crop management. The most important and common drought resistance traits function to maintain plant hydration under drought stress due to effective use of water (EUW). The state of our knowledge and the achievements in breeding for drought resistance do not support labelling drought resistance as a complex trait. The genomics road towards drought resistance is complex but we already know that the destination is much simpler. © 2011 CSIRO.

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