Silver scurf

Silver scurf is a plant disease of potato, which is caused by the anamorphic ascomycete fungus, Helminthosporium Solani. Potato tubers are the only known host of Helminthosporium solani. It is a highly specific pathogen which does not have a secondary host or alternate host. A common symptom of this disease is blemishing on the surface of the potato tubers. These blemishes are tan and/or gray due to a loss of pigment, and they are usually irregularly shaped. Also, a post-harvest symptom can be shrinkage and shriveling of the outer tissue of the potato due to water loss. Black spots can also be found on the surface of infected tubers, which are a sign of the disease. These are made up of conidia and conidiophores of the pathogenic fungus. The conidia are characterized by being very darkly melanized and having multiple pseudosepta. Another characteristic of this fungus is the absence of motile spores.

Like with many other fungal plant diseases, a diagnosis can be made by looking for the specific sexual structures of the fungus and observing them for the specific characteristics of silver scurf. Another way that silver scurf can be diagnosed is through molecular techniques, such as PCR and sequencing to identify the presence of the pathogen. The primer pair, HSF19-HSR447, has been generated to be specific for amplifying only a section of Helminthosporium Solani DNA.

Currently, no known host factors have been identified that have been linked to increase susceptibility or development of the disease. It seems as though the environmental conditions are what plays a major role in severity of the disease.