PhD student gains support to further her work on plant disease suppression in pastoral soils

5 February 2015
PhD student gains support to further work | Farm Research

An interest in sustainable farming is driving one young scientist’s research on naturally occurring plant disease suppression in New Zealand pastoral soil and her work has just been recognised with a prestigious grant.

Bryony Dignam, who is currently conducting her PhD research at AgResearch and the Bio-Protection Research Centre in Lincoln, is the recipient of the 2014 Kathleen Spragg Agricultural Research Trust grant aimed at furthering soil, plant and animal research of benefit to New Zealand’s pastoral industry.

Bryony’s research aims to deliver sustainable disease control options for pastoral farmers by identifying farm management practices that select for beneficial disease suppressive micro-organisms.

Soil-borne plant diseases are responsible for substantial losses in pasture production through drastic reductions in efficient use of water and nutrients, but the impacts are generally unnoticed and seriously underestimated. These diseases are difficult to control using conventional pesticides, many of which are likely to be unavailable to farmers in the future.  Inconsistent control provided by conventional techniques and increasing public concern regarding the effect of agrichemicals on the environment and human health is driving the search for environmentally safe methods for the control of soil-borne plant pathogens. The diversity and activity of these disease suppressive microbial communities is the topic of her PhD.

Bryony will use the grant to visit the Netherlands in 2015 where she will work with Professors George Kowalchuk (University of Utrecht) and Jos Raaijmakers (University of Wageningen), both world-leading international experts in plant disease suppression and soil microbial ecology.

“I think everyone should have a great interest in sustainable farming as we’re going to have to feed a growing population,” she says.

“And what interests me in particular is that farmers are having to produce more but face increasing environmental, economic and regulatory restraints. So we hope to develop more sustainable methods of disease control that use existing farm management practices; manipulate those practices and hopefully not have the increased cost and complexity of implementation.”

Bryony is using novel approaches to determine the functional gene ecology that underpins naturally occurring disease suppression in pastoral soils.  The genes involved in plant disease suppression are genetically conserved across microbial species.

In addition to analysing the diversity and functionality of the disease-suppressive microbial community in fifty pasture soils collected from across New Zealand, Bryony has completed experiments that measure the relative impact of many ‘on farm’ management practices on the composition and functionality of the disease suppressive microbial community. Results to date suggest that manipulation of certain soil properties (in particular Soil C/P Ratio and carbon availability) may provide opportunities to manage disease suppressive soil microbial communities.

Bryony is jointly supervised by Drs Steve Wakelin and Maureen O’Callaghan from AgResearch ( and who are also both members of the Bio-Protection Research Centre team ) and Professor Leo Condron from Lincoln University. Dr Wakelin says the majority of international research to date has focussed on arable crops and associated pathogens (such as ‘take-all’ disease of wheat) so the novel pasture-based system Bryony has developed is of great value. This work underpins future measurement, prediction and management of the disease suppressive capabilities of agricultural soils.

“Traditionally our pastures have been low input sheep and beef and if there was disease in the background then we just had to take it on the chin. However, nowadays our pasture is so incredibly valuable and diverse that there’s a lot more at stake. If plants are diseased then they’re putting resources into fighting, rather than growing, so the novel pasture-based system Bryony has developed is highly valuable,” Dr Wakelin says.

Dutch researchers are undertaking leading research but a lot of their work is focussed on arable land systems, he adds.

“So, it’s a case of Bryony learning the latest and greatest technologies and techniques and coming back to apply it to our farm systems, where we have lots of pasture diversity and lots of different diseases.”