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Diagnostic tools

2 August 2011

Agronomists can now use quicker and more accurate diagnostic tools to detect fungal and bacterial pathogens on tubers, industry delegates at the SBCSR Storage Event heard.

Glyn Harper from Sutton Bridge Crop Storage Research (SBCSR) and Jeff Peters from the Food and Environment Research Agency (Fera) told visitors to the Storage Event in September that faster diagnosis of disease in store was now possible, allowing corrective action to be taken sooner.

New, quicker and more accurate diagnostic tools can help save growers and packers up to a fifth of their potatoes often lost after washing.

Detection of diseases by the industry has relied on physical examination, which has some limitations. Some diseases have similar symptoms and may not be identified early enough to prevent spread.

“Where possible, it is best to minimise disease entering into store,” said Glyn. “However, once there, it is important to minimise development and infection of other tubers.”

An example of this can be seen in recent PCL-funded research carried out by Fera and SBCSR. It demonstrated a relationship between skin spot DNA levels in tuber peel at harvest and skin spot on tubers after storage. Store managers can now use this information to effect a skin spot risk assessment and put procedures in place to minimise the economic loss as a result of this costly blemish disease.

Trials have been completed using real-time polymerase chain reaction (PCR). This technique, used by the police in forensic examination, amplifies ‘unique’ DNA from a sample to produce millions of copies to enable the pathogen to be identified from even the smallest samples. New assays are being developed that will be capable of recognising Dickeya solani.

Jeff described a new portable PCR machine already useful for identifying quarantine diseases. However, at £80 - £100 per test, it is considered too expensive for routine store testing of individual stocks.

Jeff then introduced a new and promising pathogen detection technique, . A programme funded by Hortlink, AHDB Potatoes and the Horticultural Development Company (HDC) was set up at the beginning of 2010 to modify the Loop Mediated Isothermal Amplification (LAMP) method for on-site detection in packhouses and stores. This method combines the convenience of ‘pregnancy-type’ test kits with the accuracy of PCR.

“These methods of on-site detection are of real value to store managers as they can allow implementation strategies that reduce the risk of fungal or pathogenic spread,” said Jeff. “However, store managers can also reduce the risk of disease in stores by maintaining high hygienic standards. Cleaning a store before use removes the store of crop debris and dust which can otherwise provide a carry-over for disease.”

And for the more distant future, testing for unknown organisms can be done by pyrosequencing, a very new method of massively parallel DNA sequencing. This technique can examine the entire ‘ecology’ of a sample and could be used in the future for soil health profiling.

For more information contact Glyn Harper at SBCSR on 01406 359 413 or email  gharper@potato.org.uk.

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