Research Overview

How and why do new pathogens emerge, and more specifically, what makes a pathogen a pathogen?

Emerging pathogens include both invasive species, native species that have recently made a host-jump to a novel plant species, and native species that have increased in abundance and cause greater disease due to climate change. These represent unique natural evolutionary experiments that allow us to understand what genes are selected for during an invasion or host-jump event. We can use comparative genomics of pathogen species along with closely related non-pathogenic species to determine what genes under positive selection pressure and which genes are present in pathogen species and absent in non-pathogenic microbes. We also use experimental evolution approaches, such as serial inoculation, to observe phenotypic and genotypic differences when microbes are forced to adapt to new plant hosts.

What impact will climate change have on geographic expansion, disease intensity and evolution of pathogens?

Perhaps the single biggest factor driving disease epidemiology in the future will be the role climate change will play in altering the range of pathogen species. We study pathogen epidemiology and ecology in response to climate change in both temperate and tropical ecosystems, using a combination of historical climate data, future climate predictions, surveillance of natural pathogen populations and controlled experiments to determine impacts of temperatures and CO2 concentration on pathogen evolution.

How many fungal species are in the tropics?

Current estimates of the number of fungal species globally range from 1.5 to 3 million. However, this is largely based on surveys and work done in temperate regions and there remain comparably fewer studies investigating the number of fungal species in the tropics. Our work utilizes traditional culturing approaches and molecular identification along with metagenomic approaches to estimate fungal diversity from plants, insects, soil, leaf litter and air. Developing long-term fungal datasets in tropical sites will allow us to estimate how well our sampling efforts capture the full complement of fungal species richness, and how these fungal species fluctuate between season, location and niche. 

Education

B.Sc. University of Nebraska–Lincoln, 2008

Ph.D., The Ohio State University, 2014.

Selected Publications

Wyka, S.A., McIntire, C.D., Smith, C., Munck, I.A., Rock, B.N., Asbjornsen, H., Broders, K. 2018. Effect of climatic variables on abundance and dispersal of Lecanosticta acicola spores and impact of defoliation on eastern white pine (Pinus strobus). Phytopathology. 108: 374-383.

Schuelke, T. Woeste, K., Plachetski, D., Broders, K., MacManes, M. 2017 Comparative genomics of beetle-vectored fungal pathogens reveals a reduction in genome size and independent evolution of pathogenicity of two tree pathogens. Genome Biology & Evolution. 9: 3312-3327

Wyka, S.A., Smith, C., Munck, I., Rock, B., Ziniti, B., Broders K. 2017. Emergence of white pine needle damage (WPND) in the northeastern U.S. associated with changes in pathogen pressure in response to climate change. Global Change Biology. 23: 394 – 405

Wyka, S. A. and Broders, K.D. 2016. The new family Septorioideaceae, within the Botryosphaeriales and Septorioides strobi as a new species associated with needle defoliation of Pinus strobus in the United States. Fungal Biology. 120: 1030-1040.

Broders, K. D., **Barbison, L., **Boraks, A., **Brown, J., and Boland, G. J. 2015. Recent insights into the pandemic disease butternut canker caused by the invasive pathogen Ophiognomonia clavigignenti-juglandacearum. Forest Pathology.  45: 1-8. 

Hale, I., Broders, K. D., and Broders-Iriarte, G. A. 2014. A Vavilovian approach to discovering crop-associated microbes with the potential to enhance plant immunity.  Frontiers in Plant Science, 5:492. 

Broders, K. D., Boraks, A. W., Sanchez, A. M. and Boland G. J. 2012. Population structure of the butternut canker fungus, Ophoignomonia clavigignenti-juglandacearum, in North American forests. Ecology and Evolution. 2: 2114-2127.

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