- Lead scientist
- Dr Liz Beal
- Start date
- 2010
- End date
- 2011
- Benefits to gardeners
In conjunction with the other projects currently running with Armillaria species, tests on pathogenicity would allow us to give better advice on whether plants were affected by less pathogenic species and other factors such as stress have played a role, or if a pathogenic species is attacking a healthy plant. This information could help improve the cultural aspects of control of Armillaria infections in a garden environment.
- The problem
Due to the problems in identification of the distinct species of Armillaria many assumptions have been made about conditions needed for their initial infection. It is often assumed that for an infection to occur the host must first have been stressed in some other way; however this is not always the case.
It is widely accepted, and research has proved, that A. mellea and A. ostoyae are the most pathogenic Armillaria species, dependent on host, where A. mellea is more often seen on hardwoods, and A. ostoyae on coniferous hosts. However in a garden environment, although many of the isolates found through the Armillaria survey were identified as A. mellea, it has been shown that the other main species which have been assumed more saprophytic are in fact found on living hosts. Although it is difficult to currently ascertain how much this is due to host stress from other abiotic and biotic factors.
- Approach
This project has two main constituent experiments.
The first aims to look at the response of a host plant in the field to the different species of Armillaria. The field trial will use a known highly susceptible host of Armillaria species and will be set up in such a way that the inoculum source is close enough to the host to allow infection if the species is able, but the plants are not artificially inoculated at the start of the experiment. This will allow us to see which species are able to overcome the hosts’ natural defences without the aid of external factors, such as stress or wounding.
We will also have another set of plants which have been exposed to stressful situations, mirroring those of a gardener, such as pruning, or accidental root damage, and observe whether there is a different pattern of infection in these plants.
This will enable us to gather information about the initial infection in a field environment, indicating the more pathogenic species, and also whether stress alters the ability of a less pathogenic or even a species thought to be saprophytic to infect a host.
Although much work has been carried out looking at the direct result of differing levels of pathogenicity, such as colonisation of material, the other experiment involved in this project intends to utilise enzyme assays in order to assess pathogenicity. By looking at specific enzymes it will hopefully be possible to understand the ability of the various species to be pathogenic. By looking at several different enzymes it will be possible to look at discrete areas of the infection process, for example the initial overcoming of the hosts defences, the use of host resources for growth and development, and host cell death.
Due to the collection of isolates that are held at RHS Garden Wisley it may also be possible to use both of these experiments to test for individual isolate virulence, and see if that differs across a species. This could provide extremely detailed information about the species and their role in the environment.
- Further information
Read more on honey fungus
Read the Armillaria survey
Read about the identification of Armillaria spp, using molecular methods
Behaviour of severed rhizomorphs of A. mellea and A. gallica in growing media
Effect of abiotic factors on Armillaria growth
Growth and behaviour of Armillaria in mulches
- References
Pérez Sierra A, Whitehead, D S & Whitehead, M P (1999). Investigation of a PCR-based method for the routine identification of British Armillaria species. Mycological Research 103 (12), 1631-1636