Stem rust of wheat

Stem rust is an occasional, but devastating disease of wheat. Epidemics occur when there is a carry over of stem rust from the previous season, susceptible varieties of wheat are grown, and warm humid conditions in the spring encourage disease development

Contrasting chemical environments in summertime for atmospheric ozone across major Chinese industrial regions:The effectiveness of emission control strategies

The UKCA chemistry-climate model is used to quantify the differences in chemical environment for surface O3 for six major industrial regions across China in summer 2016. We first enhance the UKCA gas-phase chemistry scheme by incorporating reactive VOC tracers that are necessary to represent urban and regional-scale O3 photochemistry. We demonstrate that the model with the improved chemistry scheme captures the observed magnitudes and diurnal patterns of surface O3 concentrations across these regions well. Simulated O3 concentrations are highest in Beijing and Shijiazhuang on the North China Plain and in Chongqing, lower in Shanghai and Nanjing in the Yangtze River Delta, and lowest in Guangzhou in the Pearl River Delta despite the highest daytime O3 production rates in Guangzhou. NOx/VOC and H2O2/HNO3 ratios indicate that O3 production across all regions except Chongqing is VOC limited. We confirm this by constructing O3 response surfaces for each region changing NOx and VOC emissions and further contrast the effectiveness of measures to reduce surface O3 concentrations. In VOC limited regions, reducing NOx emissions by 20 % leads to a substantial O3 increase (11 %) in Shanghai. We find that reductions in NOx emissions alone of more than 70 % are required to decrease O3 concentrations across all regions. Reductions in VOC emissions alone of 20 % produce the largest decrease (- 11 %) in O3 levels in Shanghai and Guangzhou and the smallest decrease (- 1 %) in Chongqing. These responses are substantially different from those currently found in highly populated regions in other parts of the world, likely due to higher NOx emission levels in these Chinese regions. Our work provides an assessment of the effectiveness of emission control strategies to mitigate surface O3 pollution in these major industrial regions, and emphasizes that combined NOx and VOC emission controls play a pivotal role in effectively offsetting high O3 levels. It also demonstrates new capabilities in capturing regional air pollution that will permit this model to be used for future studies of regional air quality-climate interactions

Post stocking survey report: Dawson River, Taroom, survey 1, 9 November 1999

In general, fish stocking of weirs can be viewed as stocking of a river system. Fish will migrate upstream in flows and in a flood flow they can successfully move downstream. Results from the post stocking survey conducted at Dawson River, Queensland (Australia) on 9 November 1999 are detailed. The purpose of the survey was to: determine the status of the sleepy cod (Oxyeleotris lineolatus) population; gain information on the fish community in the upper Dawson River; and measure the relative abundance of angling species. After 63 minutes of electrofishing, the total catch consisted of 476 fish. Bony bream dominated the catch, followed by rainbow fish, spangled perch, golden perch, freshwater jew (eel-tailed catfish), saratoga, glass perchlet and both black bream and eel. No sleepy cod were caught in this survey

Spot Form of Net Blotch Resistance in a Diverse Set of Barley Lines in Australia and Canada.

The responses of 95 barley lines and cultivars to spot form of net blotch (SFNB) caused by Pyrenophora teres f. maculata were analyzed as seedlings and adults in Australia and Canada. Cluster analyses revealed complex reaction responses. Only 2 lines (Esperance Orge 289 and TR3189) were resistant to all isolates at the seedling stage, whereas 15 lines and cultivars (81-82/033, Arimont, BYDV-018, CBSS97M00855T-B2-M1-Y1-M2-Y-1M-0Y, C19776, Keel, Sloop, Torrens, TR326, VB0111, Yarra, VB0229, WI-2477, WI2553, and Wisconsin Pedigree) were resistant toward the two Canadian isolates and mixture of Australian isolates at the adult stages. In Australian field experiments, the effectiveness of SFNB resistance in three barley cultivars (Barque. Cowabbie, and Schooner) and one breeding line (VB9104) with a different source of resistance was tested. Barque, which possessed a resistance gene that provided complete resistance to SFNB, was the most effective and showed no effect on grain yield or quality in the presence of inoculum. Generally, cultivars with seedling or adult resistance had less disease and better grain quality than the susceptible control. Dash, but they were not as effective as Barque. A preliminary differential set of 19 barley lines and cultivars for P teres I. maculata is proposed

Sensitivity of mid-19th century tropospheric ozone to atmospheric chemistry-vegetation interactions

We use an Earth-System model (HadGEM2-ES) to investigate the sensitivity of mid-19th century tropospheric ozone to vegetation distribution and atmospheric chemistry-vegetation interaction processes. We conduct model experiments to isolate the response of mid-19th century tropospheric ozone to vegetation cover changes between the 1860s and present-day and to CO2 induced changes in isoprene emissions and dry deposition over the same period. Changes in vegetation distribution and CO2 suppression of isoprene emissions between mid-19th century and present-day, lead to decreases in global isoprene emissions of 19% and 21% respectively. This results in increases in surface ozone over the continents of up to 2 ppbv and of 2-6 ppbv in the tropical upper troposphere. The effects of CO2 increases on suppression of isoprene emissions and suppression of dry deposition to vegetation are small compared with the effects of vegetation cover change. Assuming present-day climate in addition to present-day vegetation cover and atmospheric CO2 concentrations, leads to increases in surface ozone concentrations of up to 5 ppbv over the entire northern hemisphere (NH), and of up to 8 ppbv in the NH free troposphere, compared with a mid-19th century simulation. Ozone changes are dominated by: 1) the role of isoprene as an ozone sink in the low NOx mid-19th century at30 mosphere, and 2) the redistribution of NOx to remote regions and the free troposphere via PAN (peroxyacetyl nitrate) formed from isoprene oxidation. We estimate a tropospheric ozone radiative forcing of 0.264W m−2 and a sensitivity in ozone radiative forcing to mid-19th century to present-day vegetation cover change of -0.012W m−2