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Potato pathologist discusses the emergence and prevalence of potato mop top virus

In a recent presentation, Dr. Julie Pasche, potato pathologist at North Dakota State University (NDSU), discusses the emergence and prevalence of potato mop top virus (PMTV).

Dr. Pasche says in her presentation that potato mop top virus is present in many potato growing countries around the world. It?s been a serious problem in Europe for decades. Studies that were conducted in 2001 and 2002 in the US and Canada looked at about three thousand seed lots and found that approximately four percent of them were positive for PMTV. Unfortunately, in this study no province or state distribution data was presented so at that time we did not know where the pathogen was.

Dr. Pasche points out that another interesting finding with this study was that they looked at the virus strains in the US and Canada, and found that they were 100 percent similar to each other, and then compared the North American strains to European strains and found that they were 97 percent similar. This is important, Dr. Pasche says, because when we look at things like genetic resistance and other control measures we know that we?re dealing with the same pathogen population.

According to Dr. Pasche, PMTV has been officially reported in seven states in the US starting with Maine in 2003. In addition to that it has been recently detected in a couple of other states, but 3 of these have not been officially reported.

PMTV has a complex genome with three parts, Dr Pasche says, but not all plant tissues may contain the completely assembled virus particle. The incomplete virus particle may still be infectious and capable of movement in the plant, but they might not cause symptoms or be moved to all tubers or stems.

This is important because when we look at detecting the virus, one tuber may test negative but other tubers produced by that same plant may be infected, according to Dr. Pasche. She says PMTV can cause foliar symptoms, including stunting, modeling chevrons and yellow blotches or rings, but these are only rarely seen in the field. Foliar symptoms occur from seed infections – they do not develop from soil borne infections. These foliar symptoms can be easily confused with those induced by alfalfa mosaic virus and typically occur on lower leaves.

The presentation below can also be watched on YouTube here.

Source: Dr Andy Robinson, North Dakota State University (NDSU)
Cover photo credit: Ipsita Mallik

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