Bread wheat (Triticum aestivum L.) is one of the most important food crops, however it is only moderately tolerant to salinity stress. To improve wheat yield under saline conditions, breeding for improved salinity tolerance of wheat is needed. We have identified nine quantitative trail loci (QTL) for different salt tolerance sub-traits in a recombinant inbred line (RIL) population, derived from the bi-parental cross of Excalibur × Kukri. This population was screened for salinity tolerance subtraits using a combination of both destructive and non-destructive phenotyping. Genotyping by sequencing (GBS) was used to construct a high-density genetic linkage map, consisting of 3236 markers, and utilised for mapping QTL. Of the nine mapped QTL, six were detected under salt stress, including QTL for maintenance of shoot growth under salinity (QG(1-5).asl-5A, QG(1-5).asl-7B) sodium accumulation (QNa.asl-2A), chloride accumulation (QCl.asl-2A, QCl.asl-3A) and potassium:sodium ratio (QK:Na.asl-2DS2). Potential candidate genes within these QTL intervals were shortlisted using bioinformatics tools. These findings are expected to facilitate the breeding of new salt tolerant wheat cultivars.

Key message Novel QTL for salinity tolerance traits have been detected using non-destructive and destructive phenotyping in bread wheat and were shown to be linked to improvements in yield in saline fields. Abstract Soil salinity is a major limitation to cereal production. Breeding new salt-tolerant cultivars has the potential to improve cereal crop yields. In this study, a doubled haploid bread wheat mapping population, derived from the bi-parental cross of Excalibur × Kukri, was grown in a glasshouse under control and salinity treatments and evaluated using high-throughput non-destructive imaging technology. Quantitative trait locus (QTL) analysis of this population detected multiple QTL under salt and control treatments. Of these, six QTL were detected in the salt treatment including one for maintenance of shoot growth under salinity ( QG (1 – 5) .asl - 7A ), one for leaf Na + exclusion ( QNa.asl - 7A ) and four for leaf K + accumulation ( QK.asl - 2B.1 , QK.asl - 2B.2 , QK.asl - 5A and QK:Na.asl - 6A ). The beneficial allele for QG (1 – 5) .asl - 7A (the maintenance of shoot growth under salinity) was present in six out of 44 mainly Australian bread and durum wheat cultivars. The effect of each QTL allele on grain yield was tested in a range of salinity concentrations at three field sites across 2 years. In six out of nine field trials with different levels of salinity stress, lines with alleles for Na + exclusion and/or K + maintenance at three QTL ( QNa.asl - 7A , QK.asl - 2B.2 and QK:Na.asl - 6A ) excluded more Na + or accumulated more K + compared to lines without these alleles. Importantly, the QK.asl - 2B.2 allele for higher K + accumulation was found to be associated with higher grain yield at all field sites. Several alleles at other QTL were associated with higher grain yields at selected field sites.

Soil salinity can severely reduce crop growth and yield. Many studies have investigated salinity tolerance mechanisms in cereals using phenotypes that are relatively easy to measure. The majority of these studies measured the accumulation of shoot Na+ and the effect this has on plant growth. However, plant growth is reduced immediately after exposure to NaCl before Na+ accumulates to toxic concentrations in the shoot. In this study, nondestructive and destructive measurements are used to evaluate the responses of 24 predominately Australian barley (Hordeum vulgare L.) lines at 0, 150 and 250mM NaCl. Considerable variation for shoot tolerance mechanisms not related to ion toxicity (shoot ion-independent tolerance) was found, with some lines being able to maintain substantial growth rates under salt stress, whereas others stopped growing. Hordeum vulgare spp. spontaneum accessions and barley landraces predominantly had the best shoot ion independent tolerance, although two commercial cultivars, Fathom and Skiff, also had high tolerance. The tolerance of cv. Fathom may be caused by a recent introgression from H. vulgare L. spp. spontaneum. This study shows that the most salt-tolerant barley lines are those that contain both shoot ion-independent tolerance and the ability to exclude Na+ from the shoot (and thus maintain high K+:Na+ ratios).

Background: In wheat, grain filling is closely related to flag leaf characteristics and function. Stomata are specialized leaf epidermal cells which regulate photosynthetic CO2 uptake and water loss by transpiration. Understanding the mechanisms controlling stomatal size, and their opening under drought, is critical to reduce plant water loss and maintain a high photosynthetic rate which ultimately leads to elevated yield. We applied a leaf imprinting method for rapid and non-destructive phenotyping to explore genetic variation and identify quantitative traits loci (QTL) for stomatal traits in wheat grown under greenhouse and field conditions.Results: The genetics of stomatal traits on the adaxial surface of the flag leaf was investigated using 146 double haploid lines derived from a cross between two Australian lines of Triticum aestivum, RAC875 and Kukri. The drought tolerant line RAC875 showed numerous small stomata in contrast to Kukri. Significant differences between the lines were observed for stomatal densitity and size related traits. A negative correlation was found between stomatal size and density, reflecting a compensatory relationship between these traits to maintain total pore area per unit leaf surface area. QTL were identified for stomatal traits on chromosomes 1A, 1B, 2B, and 7A under field and controlled conditions. Most importantly some of these loci overlap with QTL on chromosome 7A that control kernel number per spike, normalized difference vegetation index, harvest index and yield in the same population.Conclusions: In this first study to decifer genetic relationships between wheat stomatal traits and yield in response to water deficit, no significant correlations were observed among yield and stomatal traits under field conditions. However we found some overlaps between QTL for stomatal traits and yield across environments. This suggested that stomatal traits could be an underlying mechanism increasing yield at specific loci and used as a proxy to track a target QTL in recombinant lines. This finding is a step-forward in understanding the function of these loci and identifying candidate genes to accelerate positional cloning of yield QTL in wheat under drought.

Salinity stress has significant negative effects on plant biomass production and crop yield. Salinity tolerance is controlled by complex systems of gene expression and ion transport. The relationship between specific features of mild salinity stress adaptation and gene expression was analyzed using four commercial varieties of bread wheat (Triticum aestivum) that have different levels of salinity tolerance. The high-throughput phenotyping system in The Plant Accelerator at the Australian Plant Phenomics Facility revealed variation in shoot relative growth rate and salinity tolerance among the four cultivars. Comparative analysis of gene expression in the leaf sheaths identified genes whose functions are potentially linked to shoot biomass development and salinity tolerance. Early responses to mild salinity stress through changes in gene expression have an influence on the acquisition of stress tolerance and improvement in biomass accumulation during the early "osmotic" phase of salinity stress. In addition, results revealed transcript profiles for the wheat cultivars that were different from those of usual stress-inducible genes, but were related to those of plant growth. These findings suggest that, in the process of breeding, selection of specific traits with various salinity stress-inducible genes in commercial bread wheat has led to adaptation to mild salinity conditions.

Over the last decade, biological sciences have been revolutionised by the adoption of high-throughput omics technologies, and many of the discoveries that have underpinned this revolution have now been adopted for use in plant phenotyping. The field of whole-plant phenomics resulting from this combines robotics, image capture and high-performance computational analysis and provides plant scientists with the ability to characterise dozens of phenotypes on thousands of plants daily. The throughput and accuracy offered by plant phenomics systems, which are often designed for direct experimentation in crops like barley, are providing plant physiologists and geneticists with the opportunity to benefit from the ever-increasing genomics resources that are available in these species. Combined with the ability to record data in multiple visible and non-visible wavelengths and to study root structure or entire field trial sites, these techniques are providing previously unachievable insights into many aspects of plant biology and productivity. Phenomics research in barley is generating novel data about response and tolerance to drought and salinity stress, and applications are being developed that will enhance our understanding of growth patterns, water and nutrient usage and photosynthetic efficiency, among many other traits. At the same time, phenomics techniques are being applied in large-scale genetic screening and breeding systems.

Background and Aims: For Vitis vinifera L. berries late in ripening, varietal differences have been found in tissue vitality and water relations linked to berry shrivel. Berry shrivel impacts on quality attributes. Here we quantified berry tissue vitality and shrivel across a broader range of varieties. Methods and Results: Berries from 22 varieties (similar °Brix at harvest maturity) were sectioned longitudinally at the centre and stained to measure tissue vitality and morphology. An analysis tool using MATLAB®R2008a (The Mathworks, Inc, Natick, MA, USA) quantified vitality and morphology, from which a shrivel index was developed. There was a correlation between shrivel and vitality across all varieties, such that greater vitality was associated with less shrivel. Similar within-variety correlations occurred for some varieties. Three clusters were identified across the varieties that reflected different degrees of tissue vitality and shrivel. Patterns of tissue vitality within the berry were also identified that appeared to differentiate between white and red winegrape varieties. Conclusion: Tissue vitality and shrivel indices separated varieties into distinct clusters that indicates mechanistic differences in the way cell vitality in the mesocarp is linked to berry water relations. Significance of the Study: Cell death before harvest may impact on berry quality. Tools to identify the onset of cell death and shrivel may allow more refined measures of quality and maturity assessment.

Weight loss in Vitis vinifera L. cv. Shiraz berries occurs in the later stages of ripening from 90–100 days after anthesis (DAA). This rarely occurs in varieties such as Chardonnay and Thompson seedless. Flow rates of water under a constant pressure into berries on detached bunches of these varieties are similar until 90–100 DAA. Shiraz berries then maintain constant flow rates until harvest maturity, and Chardonnay inflow tapers to almost zero. Thompson seedless maintains high xylem inflows. Hydraulic conductance for flow in and out of individual Shiraz and Chardonnay berries was measured using a root pressure probe. From 105 DAA, during berry weight loss in Shiraz, there were significant varietal differences in xylem hydraulic conductance. Both varieties showed flow rectification such that conductance for inflow was higher than conductance for outflow. For flow into the berry, Chardonnay had 14% of the conductance of Shiraz. For flow out of the berry Chardonnay was 4% of the conductance of Shiraz. From conductance measurements for outflow from the berry and stem water potential measurements, it was calculated that Shiraz could loose ~7% of berry volume per day, consistent with rates of berry weight loss. A functional pathway for backflow from the berries to the vine via the xylem was visualised with Lucifer Yellow CH loaded at the cut stylar end of berries on potted vines. Transport of the dye out of the berry xylem ceased before 97 DAA in Chardonnay, but was still transported into the torus and pedicel xylem of Shiraz at 118 DAA. Xylem backflow could be responsible for a portion of the post-veraison weight loss in Shiraz berries. These data provide evidence of varietal differences in hydraulic connection of berries to the vine that we relate to cell vitality in the mesocarp. The key determinates of berry water relations appear to be maintenance or otherwise of semi permeable membranes in the mesocarp cells and control of flow to the xylem to give variable hydraulic connection back to the vine.

Some varieties of Vitis vinifera L. can undergo berry weight loss during later stages of ripening. This defines a third phase of development in addition to berry formation and berry expansion. Berry weight loss is due to net water loss, but the component water flows through different pathways have remained obscure. Because of the very negative osmotic potential of the cell sap, the maintenance of semipermeable membranes in the berry is required for the berry to counter xylem and apoplast tensions that may be transferred from the vine. The transfer of tension is determined by the hydraulic connection through the xylem from the berry to the vine, which changes during development. Here we assess the membrane integrity of three varieties of V. vinifera berries (cvv. Shiraz, Chardonnay and Thompson seedless) throughout development using the vitality stains, fluorescein diacetate and propidium iodide, on fresh longitudinal sections of whole berries. We also measured the xylem pressure using a pressure probe connected to the pedicel of detached berries. The wine grapes, Chardonnay and Shiraz, maintained fully vital cells after veraison and during berry expansion, but began to show cell death in the mesocarp and endocarp at or near the time that the berries attain maximum weight. This corresponded to a change in rate of accumulation of solutes in the berry and the beginning of weight loss in Shiraz, but not in Chardonnay. Continuous decline in mesocarp and endocarp cell vitality occurred for both varieties until normal harvest dates. Shiraz grapes classified as high quality and sourced from a different vineyard also showed the same death response at the same time after anthesis, but they displayed a more consistent pattern of pericarp cell death. The table grape, Thompson seedless, showed near to 100% vitality for all cells throughout development and well past normal harvest date, except for berries with noticeable berry collapse that were treated with giberellic acid. The high cell vitality in Thompson seedless berries corresponded to negative xylem pressures that contrasted to the slightly positive pressures for Shiraz and Chardonnay. We hypothesise that two variety dependent strategies exist for grapevine berries late in development: (1) programmed cell death in the pericarp and loss of osmotically competent membranes that requires concomitant reduction in the hydraulic conductance via the xylem to the vine; (2) continued cell vitality and osmotically competent membranes that can allow high hydraulic conductance to the vine.

Due to current environmental issues concerning the use of water for irrigation, the improvement of crop water-use efficiency and a reduction in water consumption has become a priority. New irrigation methods that reduce water use, while still maintaining production have been developed. To optimise these techniques knowledge of above- and below-ground plant physiological responses is necessary. During growth, plant roots are exposed to cycles of wetting and drying in normal rain-fed and irrigation situations. This review concentrates on the below-ground aspects, in particular the water permeability of roots. Significant research has been conducted on the root anatomy and hydraulic conductivity of desert plants subjected to wetting and drying. Major intrinsic proteins (MIPs), most of which show aquaporin (water-channel) activity are likely to be involved in balancing the water relations of the plants during water deficit. However, many MIPs seem to allow permeation of other small neutral solutes and some may allow permeation of ions under certain conditions. The ability of the plant to rapidly respond to rewetting may be important in maintaining productivity. It has been suggested that aquaporins may be involved in this rapid response. The down-regulation of the aquaporins during dry conditions can also limit water loss to the soil, and intrinsic sensitivity of aquaporins to water potential is shown here to be very strong in some cases (NOD26). However, the response of aquaporins in various plant species to water deficits has been quite varied. Another component of aquaporin regulation in response to various stresses (hypoxia/anoxia, salinity and chilling) may be related to redistribution of flow to more favourable regions of the soil. Some irrigation techniques may be triggering these responses. Diurnal fluctuations of root hydraulic conductance that is related to aquaporin expression seem to match the expected transpirational demands of the shoot, and it remains to be seen if shoot-to-root signalling may be important in regulation of root aquaporins. If so, canopy management typical of horticultural crops may impact on root hydraulic conductance. An understanding of the regulation of aquaporins may assist in the development of improved resistance to water stress and greater efficiency of water use by taking into account where and when roots best absorb water.

Berries of Vitis vinifera L. cv Shiraz can undergo weight loss during later stages of ripening. Existing published views on how weight loss occurs are based on changes in capacity of the vascular system to import water during development (McCarthy and Coombe, Australian Journal of Grape and Wine Research, 5, 17–21, 1999). One important element of these views is the proposed cessation of water flow through the xylem after veraison. We have now measured the water flow into berries of Shiraz and Chardonnay as they develop using the pressure probe and the high pressure flow meter (HPFM). The pressure probe connected to the pedicel of individual berries provided measurements of single berry hydraulic conductance. By systematic excision of tissue segments of the berry and pedicel we determined where in the pathway hydraulic conductance changed during development. The HPFM was used on whole bunches showing that berries (including pedicels) represent parallel high hydraulic resistances and that the hydraulic resistance of the bunch axis was rather small. The hydraulic conductance per berry could be determined from excision experiments. There was close agreement between the pressure probe and HPFM measurements. Both showed a ten-fold reduction in hydraulic conductance of whole berries from veraison to full ripeness. Shiraz had hydraulic conductances that were 2- to 5-fold higher than those for Chardonnay. Shiraz maintained a higher hydraulic conductance past 90 days after flowering than Chardonnay. The decrease in hydraulic conductance occurred in both the distal and proximal parts of the berry for both varieties. The pressure probe also provided measurements of the xylem pressure that non-transpiring berries could develop. These pressures were –0.2 to –0.1 MPa until veraison and increased to zero when the juice osmotic potential reached about –3 MPa in Chardonnay and –4 MPa in Shiraz. The results suggest values of the reflection coefficient of the osmotic barrier around the xylem vessels of about 0.1–0.2 at veraison decreasing to 0 at harvest. It is suggested that in addition to changes in xylem anatomy, aquaporins in berry membranes may play a role in regulating hydraulic conductance. Water movement from the berry back to the parent vine via the xylem (backflow) may be an important component of berry weight loss in Shiraz, particularly if the phloem ceases functioning at high osmotic potentials near maximum weight. Backflow could account for a weight loss of 43 mg per day in Shiraz berries for a relatively small gradient of 0.1 MPa.