Scientists create a new technique to combat scourge of potato crops

By using DNA sequencing to make pathogen-specific probes, researchers are able to detect and count the deadly bacteria in soil and on plant surfaces and advise growers on the best method of disease control.

Currently, there are more than a dozen different kinds of scab-producing Streptomyces that affect potato crops worldwide. These filamentous pathogens can penetrate expanding plant cells, including potato tubers, producing raised or pitted scab-like lesions.

S. scabies is pathogenic due to its ability to produce thaxtomin, a protein that breaks down the walls of growing cells, which is encoded on a short segment of DNA transferred during mating. This gives the bacterium the ability to infect any elongating part of a plant that is underground. It is these thaxtomin biosynthethic genes that have been used to develop the pathogen-specific probes.

The potato crop is propagated vegetatively and when infected seed tubers are shipped around the globe, the harmful bacteria get a free ride to new production areas. It is not uncommon to find more than one scab-producing species in the same place, and by using the new probes, scientists can target all known variants. With further advancements in DNA analysis, even better techniques to identify these pathogens and prevent disease may be developed in the future.

Other features in the May 2007 issue of Microbiology Today include:

• An introduction to the actinobacteria (page 60)
• Good, bad, but beautiful: the weird and wonderful actinobacteria (page 68)
• Corynebacteria: the good guys and the bad guys (page 74)
• The mycobacteria (page 78)
• Comment: Review of UK microbial science (page 100)
These are just some of the articles that appear, together with all the regular features and reports of Society activities.