A new diagnostic technique has been developed to identify tomato root mat disease infection in young tomato plants, enabling growers to respond before symptoms become severe. Root mat disease now affects almost nine out of 10 tomato nurseries across the UK.
The disease leads to a hormone imbalance that can cause root proliferation in tomato plants. Affected plants often produce fruit outside of retailer specifications and root systems can become more susceptible to infection by other pathogens. In rare cases, root systems can become so dense that the plant can no longer take up water effectively.
During the past year, research at Fera Science, funded by AHDB Horticulture, has been developing a molecular diagnostic technique. Root mat is established when the bacterium Rhizobium radiobacter releases plasmids, which are self-contained pieces of DNA. Genes on the plasmids then become incorporated alongside those of the host tomato roots, facilitating further infections and inducing the root mat symptoms.
Researchers established that the incorporated plasmid genes of the UK root mat pathogens could be detected by the same kind of test that has become widely used to pick up and measure other plant pathogens. However, Fera first had to devise a new DNA extraction method to obtain the relevant DNA sequences directly from root tissue.
The method that is in development has shown to be as effective and accurate as previous more laborious techniques. This method should enable young propagation material to be screened for infection before transplanting. For further details on project PE 029, see horticulture.ahdb.org.uk.