Diseases of Potatoes: Bacterial Ring Rot

 
 
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 Just when we think we know everything about Bacterial Ring Rot (BRR) it jumps back on us like a bent penny. All that we think that we know about it is written in the fact sheet "Understanding Bacterial Ring Rot in Potatoes," Alberta Agdex 258/635-5.

Despite every effort at eradication, this bacterial disease has turned up everywhere potatoes are grown. It's got some kind of last ditch survival mechanism that we don't understand or have discovered. Perhaps this BRR bacterium can live in exotic potato cultivars and never cause disease. A few years back in the 1980's, infected clones of Urgenta, Bel Rus, and Teton with BRR bacteria but after growing on these clones for a few years, the BRR bacteria disappeared in these three cultivars. Had the bacteria vanished or were they present at a level that made them undetectable to the detection technology at that time.

We're not alone in Canada in combating BRR since in the last few years this disease has become widespread in Europe after it was thought that this disease was virtually eradicated. In 2003, BRR has been reported from 1 farm in Wales and 2 farms in England. It is suspected that at least two sources of BRR infected potatoes were introduced into the UK where some 300,000 to 400,000 acres are grown annually. The Welsh BRR infection originated from tubers supplied by a Dutch grower in the Netherlands. The original source of BRR in England has yet to be traced. In recent years, BRR has caused problems in France, Germany, the Netherlands and Denmark.

How bacterial ring rot has reappeared in seed potatoes remains a mystery. The litigious disease thought to have been eliminated from the United Kingdom a very long time ago has now (2002) appeared in at least 4 farms in England and Wales.

What to look for?


Photo: Evans
The Irish Orchid

Potato flowers are typically white, ping or purple

Photo: Evans
Alberta seed potato production now second only to PEI

Photo: Evans
Bacterial Ring Rot (BRR) Research Plots. The late John Stenrue, BRR inspector, was reputed to spot a ring rot infestation for 100 paces.
Photo: Evans
Old Federal poster depicting BRR the scourge of the potato industry at the early part of the 20th century

Photo: Evans
BRR on highly or susceptible cultivars generally causes complete tuber rotting soon after harvest.
Photo: Evans
BRR infection causes total tuber rot in susceptible potato cultivars sometimes prior to harvest

Photo: Evans
BRR in Russet Burbank may have a few slight cracks. This cultivar shows a good degree of resistance to BRR
Photo: Evans
Not the ring pattern of BRR - following the major vascular tissue inside the potato. In some cultivars the BRR infection may not proceed further in storage.

Photo: Evans
BRR cause major yield loses in very susceptible cultivars even before harvest.
Photo: Evans
BRR trial with very many different potato cultivars from total resistance to extreme susceptibility.

Photo: Evans
Norchip - very highly susceptible to BRR.
Photo: Evans
Russet Burbank - somewhat resistant to BRR and not that easily infected.

Photo: Evans
Deseree - highly resistant to BRR.
Photo: Evans
Bel Rus - very resistant to BRR.

Photo: Evans
Pontiac - highly susceptible to BRR.
Photo: Evans
An elastic band binding healthy Pontiac potato halves to a symptomless Teton, Bel Rus and Urgenta potato halves. The Teton, Bel Rus and Urgent arose from parent tubers that had been deliberately inoculated with an undiluted culture of BRR the previous year.

Photo: Evans
Ten tubers each of Teton, Bel Rus and Urgent all resistant to BRR were bound to healthy Pontiac potato halves and planted out in replicate trials with lots of checks
Photo: Evans
Around 70% of the elastic bound Pontiacs bound to the Bel Rus, Teton and Urgenta halves showed up with BRR infections after being bound to the symptomless potato cultivars. Note the wilted Pontiac stem in the centre of this experiment.1
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Photo: Evans
In order for the BRR bacteria to move from the seed piece to new tubers, it must first pass from the infected tuber into the transport system of the stem.

Photo: Evans
In resistant cultivars, the BRR bacteria may not enter if any of the new tubers in sufficient quantity to cause an obvious rot.

Stem pieces cut next to the old tuber are the best possible place to find the BRR bacteria even in resistant cultivars seed.
.

Photo: Evans
Cut stem end of a potato vine.
Photo: Evans
Gentle squeezing may produce a milky fluid - obvious signs of the BRR bacteria.

Photo: Evans
In low levels of BRR bacterium in the stem piece a pair of needle-nosed forceps was used to squeeze the stem.
Photo: Evans
The old technique was to demonstrate the presence of gram positive staining bacteria, a method now superseded by modern technology.

Photo: Evans
From the mid-eighties to the present time BRR was thought to be eliminated from Alberta seed potato stocks.
Photo: Evans
Elimination of BRR coincided with a steady and continuing rise in the export seed potato sales for distribution in the U.S.
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Clavibacter michiganensis subsp. sepedonicus

Photo: Evans
Rosette stage; mid to late August
Typical of Russet Burbank which is somewhat resistant to this disease.

Photo: Evans
Bacterial Ring Rot symptoms in Teton. Tuber disease symptoms are rarely visible in such resistant varieties, but the bacteria has been shown to be present in the absence of any disease symptoms.

Photo: Evans
One stem totally wilted. Late August early September typical of Russet Burbank infection when only some of the tubers may show obvious BRR disease.
Photo: Evans
Mild internal symptoms of Bacterial Ring Rot; Typical of a resistant Russet Burbank infection following harvest.

Photo: Evans
Severe internal symptoms of Bacterial Ring Rot; Typical of very susceptible cultivars e.g. Norland which can rot prior to harvest.
Photo: Evans
Some potato cultivars e.g. Teton, Deseree and Urgent are very resistance to Bacterial Ring Rot, no symptoms may ever show even if the BRR bacteria are present and readily recovered.

Photo: Letal
Old method of Bacterial Ring Rot diagnosis; gram stain showing BRR bacteria. An old but reliable method abandoned in 1990.
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1 The research was done by Evans and Stenrue in 1983 and showed for the first time ever that the BRR bacterium could be carried completely symptomless in apparently healthy tubes. The symptomless resistant tuber could transfer the BRR bacterium to susceptible potato cultivars

Photographs and information assembled and prepared for ARD by Dr. Ieaun R. Evans Agri-Trend Agrology Ltd.
 
 
 
 
For more information about the content of this document, contact Robert Spencer.
This document is maintained by Shelley Barkley.
This information published to the web on December 21, 2003.
Last Reviewed/Revised on April 7, 2014.