Genetic association of stomatal traits and yield in wheat grown in low rainfall environments

Published: 4 July 2016Background: 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.Fahimeh Shahinnia, Julien Le Roy, Benjamin Laborde, Beata Sznajder, Priyanka Kalambettu, Saba Mahjourimajd, Joanne Tilbrook and Delphine Fleur

The Koolungar Moorditj Healthy Skin Project: Elder and Community Led Resources Strengthen Aboriginal Voice for Skin Health

In partnership with local Aboriginal Community Controlled Health Organisations, the Elder-led co-designed Koolungar Moorditj Healthy Skin project is guided by principles of reciprocity, capacity building, respect, and community involvement. Through this work, the team of Elders, community members, clinicians and research staff have gained insight into the skin health needs of urban-living Aboriginal koolungar (children); and having identified a lack of targeted and culturally appropriate health literacy and health promotion resources on moorditj (strong) skin, prioritised development of community-created healthy skin resources. Community members self-appointed to Aboriginal Community Advisory Groups (CAG) on Whadjuk (Perth) and Wardandi (Bunbury) boodjar (land/place) provided local leadership and led the development of moorditj skin resources. Over several online and face-to-face meetings facilitated by an Aboriginal project officer, CAG members shared local perspectives and cultural knowledge to develop and inform the messaging, medium, and dissemination of health literacy and health promotion resources for healthy skin. All CAG-created research approaches, resources and materials were presented to the Elder Researchers for discussion, final review, and implementation by the project team. Culturally appropriate moorditj skin resources, designed by community for community, build on knowledge of healthy skin to achieve moorditj skin and moorditj health for urban-living Aboriginal koolungar

Characterising weight loss in Vitis vinifera Shiraz berries at sub-optimal maturity.

Post-veraison and prior to reaching harvest maturity, Vitis vinifera cv Shiraz berries lose weight where other varieties such as Chardonnay and Thompson Seedless do not. The berry weight loss occurs in the later stages of ripening from 90-100 days after anthesis. 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. A method of direct measurement was developed using a pressure probe to measure the pedicel xylem hydraulic conductance of single detached berries through development. The probe measured the pressure developed in the xylem of non-transpiring berries. Pre-veraison, negative xylem pressures of -0.2 to -0.1 MPa were measured, increasing to around zero between veraison and 90 days after anthesis. The pressures around zero were maintained until harvest when the berry juice osmotic potential was around -3 MPa for Chardonnay and -4 MPa for Shiraz. Since cell turgor is low in the berry, this indicates that the juice osmotic potential is not translated into negative xylem pressure. It may suggest that the reflection coefficient of cell membranes surrounding the berry xylem in both varieties changes from close to 1 pre-veraison, to about 0.1-0.2 at veraison and decreases to 0 at harvest. Both varieties showed a ten-fold reduction in hydraulic conductance from veraison to full ripeness. Shiraz had conductances that were two to five fold larger than Chardonnay, and maintained higher conductance from 90 days after anthesis, the period where berry weight loss occurred. In both varieties the hydraulic conductance reduced in the distal and proximal portions of the berries from veraison. Focusing on xylem hydraulic conductance into and out of berries from 105 days after anthesis and during berry weight loss in Shiraz, significant varietal differences in xylem hydraulic conductance were found. Both varieties showed flow rectification such that conductance for inflow was higher than conductance for outflow. For flow in to 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 lose about 7% of berry volume per day, consistent with rates of berry weight loss. Using a XYL’EM™ flowmeter, flow rates of water under a constant pressure into berries on detached bunches of these varieties are similar until 90-100 days after anthesis. Shiraz berries then maintain constant flow rates until harvest maturity while Chardonnay inflow tapers to almost zero. Thompson Seedless maintains high xylem inflows. These data are consistent with single berry measurements with the pressure probe. 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 prior to 97 days after anthesis in Chardonnay, but was still transported into the torus and pedicel xylem of Shiraz at 118 days after anthesis. 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. 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. We assess the membrane integrity of the three varieties, Shiraz, Chardonnay and Thompson Seedless throughout development using the vitality stains, fluorescein diacetate and propidium iodide, on fresh longitudinal sections of whole 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 amore 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 gibberellic 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. I 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. Weight loss in Shiraz berries before harvest maturity for winemaking has, to date, not been manipulable by viticultural practices such as irrigation. This work shows that foliar application of molybdenum to Shiraz vines changed the time course of berry weight accumulation regardless of the timing of the application in two vineyards over two seasons. Molybdenum treatment delayed the transition of berries from phase 2 (berry weight accumulation) to phase 3 (weight loss) of development for 2 to 7 days. It also slowed sugar accumulation relative to berry weight accumulation in phase 2. Allometric analysis of abscisic acid content of berries relative to weight accumulation in phase 2 and phase 3 showed no significant differences. Fruit yields from molybdenum treated and control vines were not significantly different when harvested at the same ºBrix rather than the same day after anthesis. Pruning weights of treated vines were significantly higher than control vines, suggesting increased vigour related to increased availability of the molybdoenzyme nitrate reductase, and therefore increased potential to reduce nitrate for assimilation. Wine made from fruit of treated vines contained five times higher molybdenum than wines made from control fruit, but were still at levels safe for human consumption. Sensory analysis of wines made from molybdenum treated and control fruit indicate that organoleptic differences may be perceived in the wines because of molybdenum treatment. In summary, significant varietal differences were found in how berries isolate from the vine, with strong evidence that weight loss from Shiraz berries is caused by xylem backflow to the vine, perhaps associated with changes in aquaporin or cell membrane function in xylem associated tissue. Differences were also found in cell vitality and membrane competence across the endocarp and mesocarp of berries through development, with distinct varietal differences between the wine varieties Shiraz and Chardonnay, and the table grape Thompson Seedless. The kinetics of berry weight accumulation in Shiraz is altered by the foliar application of molybdenum to vines at anthesis and capfall, but molybdenum may affect the organoleptic qualities of wine made from the fruit.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 201

Hydraulic connection of grape berries to the vine: varietal differences in water conductance into and out of berries, and potential for backflow

© CSIRO 2009Weight 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.Joanne Tilbrook and Stephen D. Tyerma

Relative growth rates (RGRs) of seedlings of Berkut, Krichauff, Gladius and Drysdale over 0 to 7 days grown with no added NaCl (circles) or treated with 100 mM NaCl (triangles).

<p>(SE, n = 6 for Berkut and Krichauff, n = 4 for Gladius and Drysdale). RGRs of treated plants were significantly difference to RGRs of control plants (2 way ANOVA, p = 0.025).</p

Gene expression pattern for the four cultivars under control conditions.

<p>(A) Venn diagrams showing a five-fold or greater difference in expression with all possible regressions during the first 3 days of growth under control conditions compared with the starting point (day 0) of the experiments. (B) Heat maps indicating intensity of gene expression in Berkut. Log FC = log₂ (the signal intensity under saline conditions / the signal intensity under control conditions). (C) Analysis of the gene ontology of 39 genes upregulated only in Berkut under control conditions. Functional categorizations by annotation were shown as gene ontology of biological process.</p

Additional file 1: Figure S1. of Genetic association of stomatal traits and yield in wheat grown in low rainfall environments

Frequency distribution of phenotypes for stomatal size related traits and yield in the RAC875/Kukri DH lines based on means obtained over each experiment. a) Lameroo, b) Roseworthy, c) Well watered conditions in the glasshouse, d) Drought conditions in the glasshouse. Arrows indicate phenotypic values of RAC875 (R) and Kukri (K). (PPTX 264 kb

Additional file 4: Figure S3. of Genetic association of stomatal traits and yield in wheat grown in low rainfall environments

Morphological features of a single stomata. Arrows indicate aperture length (APL) and width (APW) and guard cell length (GCL) and width (GCW). Aperture area (APA) and guard cell area (GCL) were calculated by multiplying the length and width of the rectangle. (DOCX 261 kb