Comparative performance of spectral and thermographic properties of plants and physiological traits for phenotyping salinity tolerance of wheat cultivars under simulated field conditions.

Successful plant breeding in saline environments requires high-throughput phenotyping techniques to differentiate genotypes for salinity tolerance. This study employed advanced, non-destructive sensing technologies to identify traits contributing to salinity tolerance in wheat (Triticum aestivum L.). Plants were grown in large containers to simulate field conditions for control, salinity stress alone, and combined salinity and drought stress treatments. The comparative performance of spectral reflectance sensing, thermography, digital imaging, and the assessment of physiological traits of two wheat cultivars were tested at booting, anthesis and grain filling. Variation in grain yield between the two cultivars was significant for all treatments (controls, P<0.01; others, P<0.001), whereas there were no significant differences in straw DW regardless of treatment. Among the spectral and thermographic assessments, spectral indices were sufficiently sensitive to detect genotypic differences in salinity tolerance among the wheat cultivars after anthesis for the salinity alone and combined treatments. In contrast, physiological traits such as leaf water status and photosynthetic properties demonstrated no differences between the wheat cultivars for either the salinity alone or the combined treatments. These results suggest that spectral sensing has the potential for high-throughput screening of phenotypic traits associated with salinity tolerance of wheat cultivars.

Evaluating growth platforms and stress scenarios to assess the salt tolerance of wheat plants.

Crops are routinely subjected to a combination of different abiotic stresses. Simplified platforms, stress scenarios and stress protocols are used to study salt tolerance under largely controlled and uniform conditions that are difficult to extrapolate to real arid and semiarid field conditions. To address the latter deficit, this work compares a realistic stress protocol (for salinity alone, drought alone and combined salinity plus drought stress) simulating a field environment in large containers to equivalent results from a more artificial pot environment. The work was based on two wheat cultivars known to differ in their salt tolerance (salt-sensitive Sakha 61 and salt-tolerant Sakha 93). Our results showed that previously established differences in the salt tolerances of the two wheat cultivars were no longer valid when the plants were exposed to a combined stress of salinity plus drought, regardless of the growth platform. Furthermore, in comparing a simulated field root-environment (containers) with pots, our results showed an interactive effect between the different treatments and platforms for both of the investigated cultivars. We conclude that a combined salinity+drought stress scenario and a reliable growth platform are of utmost importance in screening for salt tolerance of spring wheat. In future studies, increased emphasis should be placed on combining salinity with drought stress in well suited platforms to better mimic real field conditions where salinity is present.

Spectral assessments of wheat plants grown in pots and containers under saline conditions.

Spectral measurements allow fast nondestructive assessment of plant traits under controlled greenhouse and close-to-field conditions. Field crop stands differ from pot-grown plants, which may affect the ability to assess stress-related traits by nondestructive high-throughput measurements. This study analysed the potential to detect salt stress-related traits of spring wheat (Triticum aestivum L.) cultivars grown in pots or in a close-to-field container platform. In two experiments, selected spectral indices assessed by active and passive spectral sensing were related to the fresh weight of the aboveground biomass, the water content of the aboveground biomass, the leaf water potential and the relative leaf water content of two cultivars with different salt tolerance. The traits were better ascertained by spectral sensing of container-grown plants compared with pot-grown plants. This may be due to a decreased match between the sensors' footprint and the plant area of the pot-grown plants, which was further characterised by enhanced senescence of lower leaves. The reflectance ratio R760 : R670, the normalised difference vegetation index and the reflectance ratio R780 : R550 spectral indices were the best indices and were significantly related to the fresh weight, the water content of the aboveground biomass and the water potential of the youngest fully developed leaf. Passive sensors delivered similar relationships to active sensors. Across all treatments, both cultivars were successfully differentiated using either destructively or nondestructively assessed parameters. Although spectral sensors provide fast and qualitatively good assessments of the traits of salt-stressed plants, further research is required to describe the potential and limitations of spectral sensing.

Monitoring of spasticity and functional ability in individuals with incomplete spinal cord injury with a functional electrical stimulation cycling system.

BACKGROUND: The aim of this study was to investigate the integration of motor function and spasticity assessment of individuals with spinal cord injury into cycling therapy. METHODS: Twenty-three participants with incomplete spinal cord injury performed 18 training sessions (standard deviation (SD) 14) on an instrumented tricycle combined with functional electrical stimulation. Each therapy session included a power output test to assess the participants' ability to pedal actively and a spasticity test routine that measures the legs' resistance to the pedalling motion. In addition, the required time for the therapy phases was monitored. RESULTS: The results of the power output test showed a monthly increase in power output of 4.4 W (SD 13.7) at 30 rpm and 18.2 W (SD 23.9) at 60 rpm. The results of the spasticity assessment indicate a 12.2 W (SD 9.7) reduction in resistance at 60 rpm after the FES training for the subject group with spasticity. CONCLUSION: In clinical use over a time-period of 2 years this combined form of therapy and motor function assessment was well accepted by participants. The active power output test and the spasticity test routine offered a proper tool to monitor participants' progress in functional rehabilitation and changes in spasticity.