A PCR-based method for detection of potato pathogen, Helminthosporium solani, in silver scurf infected tuber tissue and soils.

Silver scurf caused by Helminthosporium solani causes significant economic losses in table stock, seed and processing potatoes. Specific polymerase chain reaction (PCR) primers, Hs1F1/Hs2R1, from H. solani were used for the amplification of a 447-bp product from 20 tissue samples and 54 single spore H. solani isolates, from eastern Canada (27 isolates), western Canada (13 isolates) and North Dakota in USA (14 isolates), but not from other potato fungal pathogens. In addition to PCR analysis, all 54 isolates were studied using conventional detection methods, visual disease symptoms and/or colony morphology and microscopic examination of the morphology of conidiophores and conidia. The PCR assay successfully detected H. solani and the PCR results correlated well with assessments based on conventional techniques. The detection of H. solani by PCR (1 day) is rapid and offers an alternative to the time consuming conventional diagnostic techniques (4-5 weeks). Nested PCR assay was necessary for the detection of H. solani in soils and thus can provide a sensitive technique to study the epidemiology of silver scurf in soils.