Simultaneous epidemic development of scald and net blotch on single leaf layers of a spring barley crop

Background and objectives Two pathogens growing on the same leaf compete for the same resources, i.e. space and plant nutrients. This may lead to density dependent disease development. The pathogens may also influence each other directly such that the influence of one on the other is more complex than a simple function of the area of the other pathogen. Different interaction types are, for example, competition, mutualism and exploitation. The importance of such interactions for epidemics of simultaneously occurring pathogens has received little attention. The objective of this study is to investigate the simultaneous epidemic development of Rhynchosporium secalis (causing scald) and Drechslera teres (causing net blotch) on spring barley under field conditions. Materials and methods The field trial was performed with artificial inoculation of R. secalis and D. teres on three spring barley varieties differing in their susceptibility towards the pathogens. The pathogens were inoculated in three combinations: only one was inoculated, they were inoculated together, the second pathogen was inoculated 26 days after the first. A non-inoculated treatment was included. The trial had three replications. Nine plants were harvested from each plot five times during the season. Leaves were dried and disease severity and senescence observed. Only leaves with < 50 % senescence were included in the analysis. Whole-plant disease severity over time was calculated as average of disease severity on leaves weighted by leaf area. Disease development per leaf layer was evaluated by fitting an exponential model to severity data over time for each leaf layer per variety, treatment and replicate. Association between scald and net blotch severity on individual leaves was analysed using Kendall’s tau. Results and discussion Net blotch developed on all leaf layers and reached whole-plant disease severities up to 15%. Scald did not develop on upper leaf layers and whole-plant severity was less than 2%. Disease severity curves at whole-plant level showed no effect of inoculating the other pathogen. The analysis of the growth rate of each disease per leaf layer showed a significant effect of variety and leaf layer within variety but no effect of treatment. However, we observed significant negative associations between the diseases on individual leaves for several combinations of leaf layer and variety. These results show that the individual leaf approach can provide new information and underline the importance of considering interactions between pathogens in the field. Acknowledgement This work was funded by the DARCOF II project BAR-O

Vekselvirkning mellem plantesygdomme påvirker sygdomsudviklingen

Sygdomme i planter kan være forårsaget af mange forskellige mikroorganismer, og ofte vil der i en enkelt afgrøde og på én plante være flere arter tilstede samtidigt. På trods af denne erfaring har der været tradition for at forske i sygdomme enkeltvis, og betydningen på det totale sygdomsniveau af vekselvirkninger mellem de enkelte patogener er kun blevet studeret i begrænset omfang. Her beskrives vekselvirkningen mellem sygdommene bladplet og skoldplet på byg i markforsøg

Plant Biology and Biogeochemistry Department annual report 1998

The annual report from the Plant Biology and Biogeochemistry Department aims to provide a summary of our research and achievements and to give an idea of the research directions in the Department. The Department is engaged in research to establish the scientific basis for new methods in industrial and agricultural production. Through basic and applied experimental research, the Department aspires to develop methods and technology for industrial and agricultural production, exerting less stress and strain on the environment. The research approach in the Department is mainly experimental. In the autumn of 1997 it was decided to reorganize and expand the Department and in 1998 the Department includes six research programmes and special facilities. Selected departmental research activities during 1998 are introduced and reviewed in seven chapters: 1. Introduction, 2. Plant-Microbe Symbioses, 3. Plant Products and Recycling of Biomass, 4. DLF-Risø Biotechnology, 5. Plant Genetics and Epidemiology, 6. Biogeochemistry, 7. Plant Ecosystems and Nutrient Cycling. The Department’s contribution to education and training are presented. Lists of publications, papers accepted for publications, guest lectures, exchange of scientists, lectures and poster presentations at international meetings are included in the report. Names of the scientific and technical staff members, visiting scientists, Postdoctoral fellows, Ph.D. students, M.Sc. students and apprentices are also listed

Impacts of climate change on plant diseases – opinions and trends

There has been a remarkable scientific output on the topic of how climate change is likely to affect plant diseases in the coming decades. This review addresses the need for review of this burgeoning literature by summarizing opinions of previous reviews and trends in recent studies on the impacts of climate change on plant health. Sudden Oak Death is used as an introductory case study: Californian forests could become even more susceptible to this emerging plant disease, if spring precipitations will be accompanied by warmer temperatures, although climate shifts may also affect the current synchronicity between host cambium activity and pathogen colonization rate. A summary of observed and predicted climate changes, as well as of direct effects of climate change on pathosystems, is provided. Prediction and management of climate change effects on plant health are complicated by indirect effects and the interactions with global change drivers. Uncertainty in models of plant disease development under climate change calls for a diversity of management strategies, from more participatory approaches to interdisciplinary science. Involvement of stakeholders and scientists from outside plant pathology shows the importance of trade-offs, for example in the land-sharing vs. sparing debate. Further research is needed on climate change and plant health in mountain, boreal, Mediterranean and tropical regions, with multiple climate change factors and scenarios (including our responses to it, e.g. the assisted migration of plants), in relation to endophytes, viruses and mycorrhiza, using long-term and large-scale datasets and considering various plant disease control methods

Disequilibrium, adaptation and the Norse settlement of Greenland

This research was supported by the University of Edinburgh ExEDE Doctoral Training Studentship and NSF grant numbers 1202692 and 1140106.There is increasing evidence to suggest that arctic cultures and ecosystems have followed non-linear responses to climate change. Norse Scandinavian farmers introduced agriculture to sub-arctic Greenland in the late tenth century, creating synanthropic landscapes and utilising seasonally abundant marine and terrestrial resources. Using a niche-construction framework and data from recent survey work, studies of diet, and regional-scale climate proxies we examine the potential mismatch between this imported agricultural niche and the constraints of the environment from the tenth to the fifteenth centuries. We argue that landscape modification conformed the Norse to a Scandinavian style of agriculture throughout settlement, structuring and limiting the efficacy of seasonal hunting strategies. Recent climate data provide evidence of sustained cooling from the mid thirteenth century and climate variation from the early fifteenth century. Archaeological evidence suggests that the Norse made incremental adjustments to the changing sub-arctic environment, but were limited by cultural adaptations made in past environments.Publisher PDFPeer reviewe