Detection and quantification of fungal and bacterial potato pathogens in plants and soil*

Abstract

We have developed polymerase chain reaction (PCR)‐based diagnostic assays for fungal and bacterial diseases of potato together with rapid methods of DNA extraction and purification from soil and plant samples. Pathogen detection and quantification is a crucial step in the control of crop diseases. PCR primers were designed to unique sequences for specific detection of the potato blemish complex of pathogens: Spongospora subterranea (powdery scab), Streptomyces scabies (common scab), Helminthosporium solani (silver scurf), Rhizoctonia solani AG‐3 (black scurf) and Colletotrichum coccodes (black dot). A multiplex PCR test was designed with a high level of sensitivity to detect H. solani, C. coccodes , and S. scabies simultaneously in one reaction, and individual quantitative PCR assays were also developed to detect these pathogens and S. subterranea in soil and tubers. PCR‐based detection systems for the major storage‐rot pathogens of potato ( Fusarium spp., Phoma foveata, Pythium ultimum and Phytophthora erythroseptica ) are also under development. The potential of these techniques to detect and monitor these pathogen populations in soil and potato tubers for epidemiological studies is discussed.