- Lead scientist
- Geoff Denton
- Start date
- 2006
- End date
- 2011
- Keywords
Phytophthora, Pythium, Detection, Baiting, Nested PCR, Immunoassay Antibodies, UK Gardens, RHS Advisory Service.
- Benefits to gardeners
This project will compare methods for detection of Phytophthora species in plant and soil samples. Improved detection will provide gardeners with a clear, straightforward answer and enable specific advice to be given by the RHS Advisory Department. This will help with the detection of this increasingly major pathogen of garden plants.
- The problem
Phytophthora species are only visible with the aid of microscopes. Plants react to infections with discolouration of the plant tissue and in the case of Phytophthora this can cause foliar lesions, bleeding cankers, stem lesions and blackening of roots.
These plant symptoms can be caused by other diseases, pests or stresses on the plant. Detection and confirmation of the correct causal agent is paramount to being able to provide useful advice.
Detection and confirmation of Phytophthora species in samples received through the RHS Advisory Service has traditionally relied on trying to grow a live culture of the pathogen. Many molecular techniques have been developed, able to detect Phytophthora proteins or DNA directly within plant and soil samples. Research has shown these molecular techniques can detect as little as 1 to 100fg (femtograms) of DNA, 1fg is equal to 0.000000000000001g, as an example a single grain of table salt weighs approximately 100 billion femtograms.
Although these are highly sensitive and before changing our current system we need to be able to confirm they are as reliable as our existing measures. They need to be able to detect any Phytophthora species from any host plant. This is a huge order as there are around 100 Phytophthora species recorded. RHS Garden Wisley has 23,000 taxa of plants (within 1,616 genera), this gives some illustration of the number of possible hosts that we can see.
By comparing various techniques for the detection of Phytophthora species from RHS Advisory Department samples we can improve detection and give clearer advice.
- Approach
Samples received through the RHS advisory service showing typical Phytophthora symptoms are put forward for further testing. These samples are processed using three detection methods:
- Recovering a live culture of Phytophthora, using a fruit as a bait. Once a live culture is recovered, production of spore-containing structures (sporangia) is required for positive identification.
- Detection of Phytophthora using nested PCR. Regions of DNA have been shown to have specificity to different genera/families. One of these has been chosen and if this region is detected then it is recorded as a positive result.
- Detection of Phytophthora using antibodies. Commercial tests are available with embedded antibodies for the detection of Phytophthora. One of these has been chosen and the production of an appropriate band was recorded as a positive results.
This work is still ongoing but preliminary results are suggesting that recovery of a live culture is producing about 15% positive results, the detection using nested PCR is producing 75% positive results and the detection using antibodies is producing 50% positive results.
- References
Read the research paper written by Béatrice Henricot on Phytophthora ramorum
- Advisory information
Read more about Phytophthora bleeding canker
Read more on Holly leaf blight
Read about Potato and tomato blight
Advice on Phytophthora ramorum and Phytophthora kernoviae
Find out how to use commercial antibody kits
Read the Phytophthora survey
Read the study on the pathogenicity Phytophthora and Pythium on yew (Taxus baccata)
Read Pythium: A garden pathogen?