rice plants

Sun protection and diversity could be key to more productive rice crops

With a rapidly growing population, improving the yield of global food staples such as rice has become an urgent focus for plant scientists.

In a recent study published on Plant Physiology, scientists have discovered they can improve rice productivity by selecting rice varieties that are better at capturing sunlight to produce grains instead of reflecting it as heat.

The team, which included Dr Xavier Sirault from the Australian Plant Phenomics Facility’s High Resolution Plant Phenomics Centre (APPF – HRPPC), focused on rice’s natural diversity by using traditional breeding techniques to select cultivated varieties – or cultivars – that are better at converting sunlight into food.

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“We studied hundreds of plants from five rice cultivars and found that there is variation between these varieties in relation to the quantity of light they use for growth or dissipate as heat. Some of them are capable of converting more sunlight into chemical energy, producing greater leaf area over time,” said lead researcher, Dr Katherine Meacham.

When leaves intercept sunlight, this sunlight is either; 1) absorbed by the leaf and converted via the process of photosynthesis into the plants own components; leaves, grains, roots, etc. 2) dissipated as heat as an strategy to protect the proteins of the plant from sun damage (photo-protection) or, 3) re-emitted as fluorescent light. In this study, the researchers measured fluorescence to infer the quantity of energy that is either converted into food or dissipated as heat.

“Recently scientists in the US found that they can produce transgenic plants that are better at catching sunlight without getting sun damage. Our work shows that this is also achievable by taking advantage of the natural variation of rice plants,” says Professor Robert Furbank, Director of the ARC Centre of Excellence for Translational Photosynthesis and one of the authors of this study.

“What is new about our research is that scientists had previously thought there was not much variation in how efficiently leaves could absorb and use light, and the reason for this is that they were not considering the full picture and measuring the plants throughout the entire day under natural illumination. We revealed that there are considerable differences between the five rice cultivars under moderate light and that means that there is room for selecting the most efficient plants,” said Professor Furbank.

“We found that there is room for improvement in some cultivars that can result in more photosynthesis without risking the plant’s protection strategies against sunlight damage.

The scientists measured fluorescence by clipping light receptors on leaves throughout a whole day to get a full picture of how the plant uses sunlight.

Traditional breeding for photosynthetic traits has not been a common strategy in any major cereal crop, in part due to the difficulty in measuring photosynthesis in thousands of plants. However, rapid screening tools are now available to study the interaction between the genes and the way they interact with the environment.

“Using unique facilities at the Australian Plant Phenomics Facility’s High Resolution Plant Phenomics Centre we were able to follow chlorophyll fluorescence in rice canopies throughout the entire day under natural illumination. This gave us completely different results when compared to the usual 30 min measurement of leaf level light use efficiency. By combining this with digital biomass analysis using PlantScan, we could link light use efficiency with growth, revealing genetic variation in rice varieties not previously detected,” said Professor Furbank.

“Our next step is to find varieties with superior photo-protection. We can directly use these for breeding and find the genes responsible. We have the capacity to screen many thousands of rice varieties for which we have gene sequence through the International Rice Research Institute,” said Dr Meacham.

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Measuring photosynthesis.  Photo credit:  International Rice Research Institute (IRRI)

 

 

Drip-fed success

The Australian Plant Phenomics Facility (APPF) is pleased to announce the new DroughtSpotter precision irrigation platform has been fully tested and commissioned, and is now ready to support your plant phenomics research.

The DroughtSpotter is a gravimetric platform with precision irrigation allowing accurate and reproducible water application for drought stress or related experiments.

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Left:  Wheat plants on the DroughtSpotter  –  Right:  Cecilia and Viviana from Monash University harvest sorghum plants during their research

A number of pilot projects were carried out to test the platform with excellent results.

Monash University researchers, led by Associate Professor Ros Gleadow, investigated the impacts of dhurrin (a chemical that is toxic to grazing animals) on drought tolerance in sorghum plants. Plants were grown under a range of drought stresses and then harvested throughout growth for biomass characterisation, metabolomics and transcriptomic responses.

“We found the DroughtSpotter to be an excellent platform to apply accurate, reproducible amounts of water to large numbers of individual plants for growth and compositional analysis under different levels of water limitation,”said Associate Professor Gleadow.

Led by Professor Steve Tyerman, researchers from the ARC Centre of Excellence in Plant Energy Biology at the University of Adelaide and TA EEA-CONICET Mendoza, Argentina investigated the relationship between hydraulic and stomatal conductance and its regulation by root and leaf aquaporins under water stress.

“A better understanding of these mechanisms is highly relevant to irrigation scheduling and to ensure sustainable vineyard management in a context of water scarcity” said Professor Tyerman.

“The DroughtSpotter platform allowed us to achieve precise control over soil moisture and vine water stress, which was the most critical aspect to the success of this project.”

The DroughtSpotter greenhouse is available to all publicly or commercially funded researchers. For further information, please visit the APPF website or contact Dr Trevor Garnett.

To read the DroughtSpotter pilot project reports:  “Drought Response in Low-Cyanogenic Sorghum bicolor Mutants”  and  “Investigating the relationship between hydraulic and stomatal conductance and its regulation by root and leaf aquaporins under progressive water stress and recovery, and exogenous application of ABA in grapevine”

Salt tolerant genetic loci in rice exposed

Rice is a staple food for over half of the world’s population. It is also the most salt-sensitive cereal crop, with losses in yield reaching up to 69%.

In a new study published in Nature Communications collaborators from King Abdullah University of Science and Technology (KAUST) and The Plant Accelerator®, Australian Plant Phenomics Facility investigated the early responses of rice plants to moderately-saline conditions and pinpointed new salt-tolerant genetic loci.

Project lead, Professor Mark Tester (KAUST), supervised PhD student Nadia Al-Tamini’s project which grew 297 indica and 256 aus rice varieties under low and high salinity. Using a technique called ‘high-throughput non-invasive phenotyping’ plants are moved on conveyor belts, imaged daily using digital cameras to monitor biomass and shoot development, and weighed to carefully measure transpiration levels (water use).

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Dr Bettina Berger (left) and Nadia Al-Tamimi (right) in The Plant Accelerator®

“The Plant Accelerator® allowed us to analyse numerous aspects of the growth of multiple plants simultaneously,” says Professor Tester.

Using the facility’s cutting-edge technology, the researchers were able to show some genes, for example those connected with signaling processes, were important to plant growth in the first two to six days after salt application, while other genes became prominent later.

“This is perhaps the most astonishing aspect of this work – we can now obtain genetic details daily, pinpointing exactly when each locus comes into play in response to salinity,” says Professor Tester.

The results of this study could prove useful for breeding programs seeking to address yield and stress resistance to meet the demand of our increasing global population and climate challenges.

Congratulations to everyone involved in this study!!

Find the full articlewww.nature.com/articles/ncomms13342

More on Nadia Al-Tamini’s story:  https://blog.plantphenomics.org.au/2015/02/24/saudi-arabian-students-joins-plant-accelerator-team-to-investigate-salinity-tolerance-in-rice/

Professor Mark Tester, Plant Science Associate Director of the Center for Desert Agriculture Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology, Saudi Arabia, mark.tester@kaust.edu.sa, www.kaust.edu.sa/en/study/faculty/mark-tester

Dr Bettina Berger, Scientific Director, The Plant Accelerator, Australian Plant Phenomics Facility, University of Adelaide, www.plantphenomics.org.au, bettina.berger@adelaide.edu.au